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University of Nigeria Research Publications

UDOM, Bassey E.

PG/M.Sc./97/24135

Impact Of Long Term Disposal Of Sewage Sludge And Effluents On Properties And Productivity Of Nsukka

Sandy Soil

Agriculture

Soil Science

e June, 2000

IMPACY Oh' LONG 'L'EIIM DISPOSAL 0)' SEWAGX SLUDGE AND

h3'FLUENTS ON PROPEH'I'IES AND PHODUCTIVITY OF NSUKKA SANDY SOIL

UDOM, BASSEY E.

~Gi~.SC./97/24135

DEPARTMENT OF SOIL SCIENCE

UNIVERSITY OF NIGERIA

NSUKKA

W A C T O F LONG TERM D I S P O S A L O F SEWAGE SLUDGE AND

E F F L U E N T S ON P R O P E R T I E S AND P R O D U C T I V I T Y O F N S U M A SANDY S O I L

UDOM, BASSEY E.

PG/M. ~Cig'i ' /24135

A D I S S E R T A T I O N S U B M I T T E D I N P A R T I A L F U L F I L M E N T

O F THE REQUIREMLNTS FOR THE AWARD O F THE DEGREE O F MASTER

OF SCILNCE (MS.) IN SOIL S C I ~ C E (SOIL CON~I~HVATION/PHYSICS) .

DEPAHTMENT O F S O I L S C I E N C E

U N I V E S S I T Y O F N I G E R I A

NSUKKA

J U N E , 2000.

CERTIFICATION

U W M , Bassey Etim, a p o s t g r a d u a t e s t u d e n t i n t h e Department

o f S o i l S c i e n c e , w i t h t h e R e g i s t r a t i o n Number ~~ /~ .SC/97 /24135 . ,

has s a t i s f a c t o r i l y completed t h e r e q u i r e m e n t s f o r c o u r s e and

r e s e a r c h work f o r t h e degree of Master of S c i e n c e (M-SC) i n

S o i l S c i e n c e ( S o i l ~ o n s e r v a t i o n / ~ h ~ s i c s ) .

The work embodied i n t h i s d i s s e r t a t i o n i s o r i g i n a l and h a s

n o t been p u b l i s h e d o r s u b m i t t e d i n p a r t o r f u l l f o r any o t h e r .

diploma o r degree o f t h i ~ , o r any o t h e r U n i v e r s i t y .

SO$. J ..S . C . MBAG WU ( S u p e r v i s o r ) (Head o f ~ e ~ a r t m e n t )

DEDICATION

This study i s dedicated t o my dear w i f e Rossy,

t o l i t t l e Jane and Mfon-Obong, and t o a l l those

who p layed a major r o l e i n l a y i n g t h e foundation

upon which we have been a b l e t o ' b u i l d our

knowledge i n S o i l Sc ience i n Afr ica .

ACKNOWLEDGEMENT

I need t o r e c o r d my deep a p p r e c i a t i o n t o a number of peop le

and one hopes t h a t t h e s u c c e s s o f t h i s s t u d y w i l l b e a n

a c c e p t a b l e compensation f o r a l l t h e i r e f f o r t s .

1 w i l l e v e r remain g r a t e f u l and i n d e b t e d t o my s u p e r v i s o r s ,

ProI. J.S.C. Mbagwu and D r N.N. Agbim f o r ~ u p p l y i n g me wi th some

of t h e m a t e r i a l s used f o r t h e s t u d y and more i m p o r t a n t l y f o r

c o n t r i b u t i n g i d e a r , r e a c t i o n s , and comments t h a t s e r v e d a 8 t h e

s p r i n g b o a r d f o r t h e s u c c e s s of t h i s work. I wish t o e x p r e s s my

deep a p p r e c i a t i o n t o P ro f . F.O.R. Akamigbo, P r o f . M.E. Obi and

D r C.A. Igwe f o r t h e i r c o n s i d e r a b l e p r o f e ~ s i o n a l suppor t . 1 a l ~ o

wish t o acknowledge t h e c o n t r i b u t i o n o f Meuors C.J. Onyi r ioha

and A.P.A. Odo b o t h l a b o r a t o r y s t a f f i n t h e Department who

s u p e r v i s e d t h e l a b o r a t o r y p r o c e d u r e s i n t h e s tudy .

I d e e p l y wish t o t h a n k my spouse , M r s Rose B- Udom f o r

p r o v i d i n g unpa id m a t e r i a l and emot ional s u p p o r t s e r v i c e s , wi thou t

which t h i s work would n o t have been s u c c e s s f u l . I a m a l s o

g r a t e f u l t o my s tep-mother M r s Jenny O.E. Okpon, M r and M r s WON.

01010, and M r P. Anosike f o r t h e i r u n d e r s t a n d i n g , encouragement

and s u p p o r t . My a p p r e c i a t i o n a l s o goes t o a l l t h o s e who

c o n t r i b u t e d i n whatever form towards t h e s u c c e s s of t h i s ~ t u d y

b u t whose names a r e n o t mentioned due t o space .

BASSEY E. UDOM

LI TERATUHE R E V 1 EW

Effects of sewage sludge and e f f l u e n t s o n s o i l phys ica l properties

Effects of sewage s ludge and effluents on soil chemical p r o p e r t i e s

h a v y m e t a l s i n oewage sludge-treated soils

Pathogens

C W T Z R THREE:

. . 3.0 MATERIALS AND METHODS

3.1 S i t e description

3.2 F i e l d investigations

3.3 Green-house studies

3.4 L a b o r a t o r y studies

CHAPTER FOUR :

4.0 RESULTS AND DISCUSSION

4.1 S o i l morphology

4.2 S o i l p h y s i c a l p r o p e r t i e s

4.2. I T e x t u r e

4.2.2 Bulk d e n s i t y a n d p o r e s i z e d i s t r i b u t i o n

4.2.3 Water r e t e n t i o n c h a r a c t e r i s t i c s

4.2.4 S a t u r a t e d h y d r a u l i c c o n d u c t i v i t y and d i s p e r s i o n r a t i o

4.2.5 Aggregate s t a b i l i t y

403 Sodium a d s o r p t i o n r a t i o , exchangeab le sodium p e r c e n t a g e , e l e c t r i c a l c o n d u c t i v i t y , s a l t c o n c e n t r a t i o n , t o t a l c a t i o n c o n c e n t r a t i o n a n d osmot i c p r e s s u r e

4.4.1 Ekchangeable bases , a c i d i t y and b a s e s a t u r a t i o n

4.4.2 Heavy metals

4.5 R e l a t i o n s h i p s among soil p h y s i c a l p r o p e r t i e s

4.6 3 e l a t i o n s h i p s between p h y s i c a l and chemica l p r o p e r t i e s

4.7 Carbon d i o x i d e e v o l u t i o n

4.8 c o l i f o r m s a n d f e c a l c o l i f o r m s

4.9 Crop pe r fo rmance

CHAPTER FIVE:

5.0 SUbIblAHY AND CONCLUSION

APPENDICES

L I S T OE' I 'IGUHES P a ~ e

F i g u r e 1: S o i l m o i s t u r e c h a r a c t e r i s t i c c u r v e s of t h e p r o f i l e p i t s a t d i f f e r e n t d e p t h s 43

F i g u r e 2: Mean m o i s t u r e c h a r a c t e r i s t i c c u r v e s of t h e p r o f i l e p i t s 44

F i g u r e 3: Cumula t ive C 0 2 e v o l u t i o n of t h e s o i l s a t 0-30 c m and 30-60 cm d e p t h s 71

Figure 4: Mean h e i g h t o f maize plant a t weekly i n t e r v a l s for t h e sewage and non-sewage s o i l s

LIST OF TABLES

Tab le 1 : Elemen ta l c h a r a c t e r i s t i c s o f sewage s l u d g e

T a b l e 24; Somo p h y s i c u l and ~ a l i n i t y c h a r a c t e r i s t i c s of t h e 0-30 cm s o i l u sed i n t h e green-house s t u d y

Tuble 2h: Some chcmica l c h a r n c t e r i s t i c s of t h e t o p 0-30 cm s o i l u s e d i n t h e $reen-house s t u d y

T a b l e 3: C l a s s i f i c a t i o n o f e l e c t r i c a l c o n d u c t i v i t y ( E C ~ ) a t 250C and s a l i n i t y h a z a r d s

Tab le 4: Some p h y s i c a l p r o p e r t i e s o f t h e s o i l s , 36 y e a r s a f t e r sewage s l u d g e a n d e f f l u e n t s d i s p o s a l

Table 5 : Volumetr ic m o i s t u r e c o n t e n t a t s a t u r a t i o n a n d 60 cm t e n s i o n , h y d r a u l i c c o n d u c t i v i t y and d i s p e r s i o n r a t i o of t h e s o i l s , 36 y e a r s a f t e r sewage s l u d g e and e f f l u e n t s d i s p o s a l

Tab le 6 : Some s o i l c h a r a c t e r i s t i c s i n t h e sewage and non sewage d i s p o s a l a r e a s

T a b l e 7: Aggregate s t a b i l i t y of t h e s o i l , 36 y e a r s a f t e r sewage ~ l u d g e and effluents d i s p o s a l

Tab le 8: Sodium a d s o r p t i o n r a t i o , exchangeab le sodium p e r c e n t a g e , e l e c t r i c a l c o n d u c t i v i t y , s a l t c o n c e n t r a t i o n , t o t a l cation c o n c e n t r a t i o n and osmot i c p r e s s u r e of t h e s o i l , 36 years a f t e r sewage s l u d g e a n d e f f l u e n t s d i s p o s a l

Tab le 9 : The pli , o r g a n i c m a t t e r and t o t a l n i t r o g e n of t h e s o i l , 36 y e a r s a f t e r sewage and e f f l u e n t s d i s p o s a l

Tab le 10: Some exchangeab le c a t i o n s p r o p e r t i e s of t h e s o i l , 36 y e a r s a f t e r sewage s l u d g e and e f f l u e n t d i s p o s a l

Table 71: Heavy m e t a l d i s t r i b u t i o n (Fpm) i n t h e a o i l p r o f i l e s , 36 y e a r s a f t e r sewage s l u d g e and e f f l u e n t s d i s p o s a l

Tab le l 2 a : C o r r e l a t i o n be tween s o i l o r g a n i c m u t t e r , c a t i o n exchange c a p a c i t y a n d heavy m e t a l s

T a b l e 12b: C o r r e l a t i o n between c a t i o n exchange c a p a c i t y a n d heavy m e t a l s

T a b l e 13: C o r r e l a t i o n s among some s o i l p h y s i c a l p r o p e r t i e s

Table 14: C o r r e l a t i o n be tween some p h y s i c a l and chemica l p r o p e r t i e s o f t h e s o i l

Table 15: Maize and Bambara Groundnut p e r f o r m a n c e s i n t h e sewage and non sewage s o i l s

L I S T OF APPENDICES

Appendix 1: S o i l p r o f i l e d e s c r i p t i o n

Appendix 2: F i e l d r e c o r d s f o r green-house expe r imen t 96

Appendix 3 : Carbon d i o x i d e (Co2) e v o l u t i o n of t h e s o i l s at 0-30 cm and 30-60 cm d e p t h s 97

phyuicul, chomictd orrd b i o l o ~ ? ; i c c t l propcjrtiuu ul' rlrr N ~ w l t k u

sandy s o i l after i t h a s been s u b j e c t e d t o 3 6 - y e a r s of d i s p o s a l

of p a r t i a l l y t r e a t e d sewage s l u d g e and e f f l u e n t s and a l s o t o

a s o e a s t h e i m p l i c a t i o n s of s u c h d i s p o s a l on c r o p p r o d u c t i o n .

S a t q r a t e d h y d r a u l i c c o n d u c t i v i t i e s , b u l k d e n s i t i e s ,

a g g r e g a t e s t a b i l i t y and w a t e r r e t e n t i o n were h i g h l y v a r i a b l e

i n the newage soil h o r i z o n s b u t c o n s i s t e n t i n t h e h o r i z o n s

of un adjacent soil u n a f f e c t e d by t h o cowuge. C o i l o r g a n i c

matter, total N, exchangeab le Na and Ca, c a t i o n exchange

c a p a c i t y and maize performance were s i g n i f i c a n t l y enhanced

( P < o . o ~ ) i n t h e sewage t h a n t h e non-sewage s o i l .

E l e c t r i c u l c o n d u c t i v i t y , Zn, Pb, Cu, Cd, and s a l t c o n c e n t r a t i o n s

as w e l l a s o t h e r s a l i n i t y p r o p e r t i e s showed h i g h l y s i g n i f i c a n t

increase ( ~ 4 0 . 0 7 ) compared with the non-sewage s o i l . I n d e e d ,

t h e growth o f the s a l t - s e n s i t i v e t e s t c r o p (Bambara groundnut

(Vigna s u b t e r r a n e a ) ) was u n s u s t a i n a b l e until t h e sewage s o i l

was l e a c h e d o f e x c e s s sa l t . There upon, 5ts y i e l d p a t t e r n

was i d e n t i c a w i t h t h a t i n t h e non-sewage a o i l .

Nuch h i g h e r microbial a c t i v i t y (PL 0.05) was o b s e r v e d

i n t h e sewage t h a n non-sewage s o i l and t h e t o t a l and fecal

c o l i f o r m c o u n t s were much h i g h e r t h a n t h e limits imposed by U n i t e d

S t a t e s Envi ronmenta l P r o t e c t i o n Agency Un i t ed (USEPA).

x i i i

Micro- t o macro -poros i ty r a t i o s were h i g h i n t h e sewage

t r e u t a o i l b u t l ow i n t h o non-sewage coil, 'l'huo, s u t u r f i t e d

h y d r a u l i c c o n d u c t i v i t y wuu hip;hly i n f % u c n c o d by tho micro- t o

mac ro -po ros i ty r a t i o r a t h c r t h a n t h e t o t a l p o r o s i t y . A

s i g n i f i c a n t , (Pc0.05) n e g a t i v e c o r r e l a t i o n (r = -0.672)

e x i s t e d be tween s o i l organic m a t t e r and a ~ g r e g a t e s t a b i l i t y

i n t h e sewage s o i l which i n d i c a t e s t h a t o r g a n i c matter was

a c t i n g as a d i s a g g r e g a t i n g a g e n t t h e r e . However, a p o s i t i v e

(P(0 .05) , c o r r e l a t i o n , be tween o r g a n i c m a t t e r a n d a g g r e g a t e

s t a b i l f t y i n t h e non-sewage s a i l ( r = 0.7101 c o n f i r m s t h e

p o s i t i v e e f f e c t of organic m a t t e r on soil s t r u c t u r a l stability.

km,vy m o t a l r ~ (Xn and C d ) worr: t t i ~ y i f i c a n t l y c o r r e l a t e d

(Y(0 .01) with :,oil or8:rn.i~ m u t t e r in t h e ~iowugc s o i l

(r = 0.818 and 0.864, r e s p e c t i v e l y ) , but n o n - s i g n i f i c a n t

c o r r e l a t i o n were o b s e r v e d i n t h e non-sewage s o i l . T h i s

indicates t h a t l o n g t e rm a p p l i c a t i o n of sewage s l u d g e and

e f f l u e n t s w a s r e s p o n s i b l e f o r heavy m e t a l c o n t a m i n a t i o n s i n

t h i s s o i l . T h e r e f o r e , a g r i c u l t u r a l u t i l i z a t i o n o f sewage

s l u d g e and e f f l u e n t s s h o u l d b e r e s t r i c t e d t o certain c r o p s

o r , at leas t , l i m i t e d i n t e r m s of t h e amount a p p l i e d .

1 .o INTRODUCTION

'Ihe a p p l i c a t i o n of sewage s l u d g e and e f f l u e n t s t o l a n d i s ,

I n p r i n c i p l e , an e f f e c t i v e d i r p o s a l method. Not on ly does i t

p r o v i d e a s o l u t i o n t o t h e s l u d g e disposal problem, b u t i t c a n ,

prove t o b e b e n e f i c i a l t o a g r i c u l t u r a l p r o d u c t i v i t y .

S h o r t t e rm, l o w a p p l i c a t i o n o f sewage s l u d g e h a s been

demonst ra ted t o yield p o s i t i v e r e s u l t s in t h e improvement of

s o i l o r g a n i c matter ( ~ i g g i n s , 19841, i n s o i l a g g r e g a t e

stability, where problems of u n s t a b l e s o i l a g g r e g a t e s a re wide

s p r e a d (Tester, 1390; Pnliai a n d A n t i s a r i , 1993). Also such

a p p l i c a t i o n have been r e p o r t e d t o d e c r e a s e s o i l b u l k . d e n s i t y ,

i n c r e a s e water -holding c a p a c i t y a n d s a t u r a t e d h y d r a u l i c

c o n d u c t i v i t y (rclbagwu and P i c c o l o , 1990; Magesan e t aL, , 1996)

There fo re , the use of a g r i c u l t u r a l l a n d s f o r sewage sludge

and e f f l u e n t s diapoaal i s being i n c r e a s i n g l y considered i n

many c o u n t r i e s as a v a l u a b l e a l t e r n a t i v e in t h e management

o f sewage s l u d g e and e f f l u e n t s and h a s become attractive,

especially in low-organic matter soils.

The p r e s e n c e o f heavy m e t a l s such as Zn, Cd, Cu, and Pb

is t he most c r i t i c a l long- term hazard when applying s l u d g e and

e f f l u e n t s t o l a n d (Logan and Chaney, 1983). Shor t - t e rm

benefits from sludge n u t r i e n t s may be negated by long-term

d e l e t e r i o u s e f f e c t s on crop y i e l d s and q u a l i t y o r , i n t h e

case of Cd, d i r e c t human t o x i c i t y . While i t h a s g e n e r a l l y

been assumed t h a t t h e s e m e t a l s a r e immobile i n managed

a g r i c u l t u r a l s o i l s (McUride, 1995) . f a c t o r s t h a t enhance

m o b i l i t y c o u l d r e s u l t i n mare p l a n t u p t a k e o r l e a c h i n g o f t h e

m e t a l s t o t h e groundwater . These f a c t o r s i n c l u d e t h e

p r o p e r t i e s o f t h e .,metals i n q u e s t i o n , pH, a n d t h e compet ing

c a t i o n s i n s o i l s o l u t i o n .

A few o t h e r c r i t i c a l l ong- t e rm h a z a r d s r c p o r t e d i n c l u d e .

surface crusting, s o i l dispersion by monovalant i o n s t h u s

making t h e s o i l p rone t o e r o s i o n , and f o r m a t i o n of wa te r -

r e p e l l e n t waxy s u b s t a n c e s which r e d u c e f i e l d m o i s t u r e

r e t e n t i o n c a p a c i t y ( ~ e n c k i s e r and S i m a r n t a , 1 9 9 4 ) , and

t o x i c i t y on micro-organisms due t o h i g h sa l t c o n t e n t (Agbim,

et al;, 1977).

Numerous s t u d i e s have b e e n c a r r i e d o u t i n v a r i o u s

c o u n t r i e s on t h e e f f e c t o f sewage s l u d g e a n d e f f l u e n t s o n

s o i l s u n d e r g r e e n house and f i e l d c o n d i t i o n s , b u t a l m o s t all

d e a l t w i t h s h o r t - t e r m i m p a c t s e s p e c i a l l y i n deve loped

c o u n t r i e ~ ( ~ e i a n a e t a l . , 1990 a n d k r t e n s e t a l . , 1992).

L i t e r a t u r e shows t h a t long- te rm impac t o f l a n d

a p p l i c a t i o n o f sewage i n some N i g e r i a n s o i l s i s s t i l l n o t

w e l l unde r s tood . The e f f e c t s on s o i l p h y s i c a l p r o p e r t i e s

and how s u c h e f f e c t s c o r r e l a t e w i t h chemica l p r o p e r t i e s a r e

e s p e c i a l l y u n c l e a r . The a b s e n c e of s u f f i c i e n t i n f o r m a t i o n

on this topical i s s u e prompted t h i s i n v e s t i g a t i o n .

The general o b j e c t i v e o f this s t u d y was t o q u a n t i f y

changes i n s o i l p r o p e r t i e s and the r e l a t i o n of s u c h changes w i t h

crop y ie lda i n t h a t they may g ive u s e f u l d a t a f o r t h e

evaluation of t h e efficiency of management p r a c t i c e s , s u c h

as a o i l tillage o r a d d i t i o n of w a s t e o r g a n i c materials i n

o r d e r t o m a i n t a i n s o i l fertility a n d t o p r e v e n t t h e d e g r a d a t i o n

of s o i l r e s o u r c e s .

The s p e c i f i c o b j e c t i v e s were:

i) t o s t u d y t h e c h a r a c t e r i s t i c s o f t h e sewage and non-

G o W U p 3 and a f f l ~ e n t u urea, und,

i i ) t o p r e d i c t likely i m p l i c a t i o n s i n o t h e r a r e a s w i t h

similar envi ronment as t h e i n v e s t i g a t e d s i t e , and s u g g e s t

g u i d e l i n e s and a p p r o p r i a t e s t r a t e g i e s t o b e employed t o

minimize damage and maximize b e n e f i t s t o o u r s o i l s .

CHAPTER mo

LITERATURE REVIEW

Sewage s l u d g e a n d e f f l u e n t s are t h e h y p r o d u c t s of t h e

t r e a t m e n t o f domes t i c and m u n i c i p a l waste water a n d sewage.

Sewage s l u d g e i s t h e suspended b i o s o l i d s removed i n p r i m a r y ,

s e c o n d a r y , and t e r t i a r y t r e a t m e n t p r o c e s s e s r a n g i n g from 0.5

t o 3.7% suspended s o l i d s w i t h t h e l o w e s t c o n t e n t coming from

t e r t i a r y t r e a t m e n t (Logan a n d H a r r i s o n , 1995 1. The

compos i t i on o f sewage s l u d g e a n d e f f l u e n t s v a r i e s from one

t r e a t m e n t p l a n t t o a n o t h e r , depend ing on t h e extent of

t r e a t m e n t and on t h e d i f f e r e n c e s i n t h e o r i g i n a l sewage make-up.

Dorneotic und m u n i c i p a l wus te w a t e r und LiowaEo uro treu tod 80

t h a t t h e f i n a l p r o d u c t s o f s l u d g e and e f f l u e n t s may be

d i s p o s e d o f w i t h minimum a d v e r s e e f f e c t s on t h e soil and

envi ronment .

2.1 E f f e c t s o f Sewage S ludge and E f f l u e n t s on S o i l P h y s i c a l

P r o p e r t i e s

Sewage s l u d g e and e f f l u e n t s have been t r a d i t i o n a l l y

aaaaptod as sources of nutrients f o r crops and i n c i d e n t a l l y

as wendments that impart certain good p h y s i c a l p r o p e r t i e s t o

s o i l s . The e f f e c t s of l a n d n p p l i c a t i o n o f sewwe s l u d g e and

e f f l u e n t s have been r e p o r t e d t o depend on t h e t e x t u r e of t h e

s o i l ( ~ a ~ l i a i e t a l . , 1981) . Sandy s o i l s w i t h l ow s t a b i l i t y

r e spond more t h a n clay s o i l s w i t h i n h e r e n t l y h i g h s t a b i l i t y .

F o r example, t h e a p p l i c a t i o n s of 28t ha-1 of sewage s l u d g e

f o r 85 y e a r s to a clay loam s o i l was r e p o r t e d t o g i v e more

s t a b i l i z e d s t r u c t u r e a n d b o t t c r permeabil ity t o t h e oil

( u i l l i n m s and Cooke , 1491 1. Similarly, improved p e r m e a b i l i t y

W a s o b ~ e r v o d o n sandy loam s o i l i n w h i c h 6 O t ha- yr-7 of

sewage s l u d g e w a s a p p l i e d f o r 18 years .

E p s t e i n (7975) observed t h a t t h e a d d i t i o n s of sewage

s l u d g e and e f f l u e n t s t o sandy s o i l s i n c r e a s e d water -holding

c a p a c i t y , w h i l s t a d d i t i o n t o clay soil, improved s o i l t i l t h ,

reduced compaction, and i n c r e a s e d t h e a e r a t i o n of t h e r o o t i n g

environment. Improvements i n p e r m e a b i l i t y and w a t e r

p e r c o l a t i o n were a l s o r e p o r t e d f o r impermeable s o i l s treated

w i t h sewage e f f l u e n t s a t Woodland, C a l i f o r n i a ( ~ p c t e f n , 'I975 1.

Magesan e t a1*(1996) observed t h a t the app l i ca t ion of

s e c o n d a r y - t r e a t e d sewage e f f l u e n t i n c r e a s e d t h e macro-poros i ty

of a sandy l o a n from 1 1 t o 19% and the hydraul ic c o n d u c t i v i t y

from 39 t o 57 mmhr'l

P a g l i a i and A n t i s a r i (1993) observed an i n c r e a s e i n s o i l .

p o r o s i t y folLowing t h e a p p l i c a t i o n o f sewage sludge and

s t r e s s e d t h a t most of t h e i n c r e a s e was due t o t h e development

of s o i l macro-pores (7504m). The increase i n s o i l macro-.

p o r e s a c c o r d i n g t o t h e s t u d y , was p a r t i c u l a r l y impor tan t

. because of their dominant e f f e c t on r o o t growth, w a t e r

i n f i l t r a t i o n , and aeration. Martens et a1* (7992) also

observed t h e b e n e f i c i a l e f f e c t s an a o i l physical p r o p e r t i e s ,

s u c h as p o r o s i t y and m o i s t u r e r c t e n t i o n , as a r e s u l t of

i n c o r p o r a t i o n o f modera t e amoun t o 01 sewage :iludp;e and

o I f l u e n t s i n t o t h e [ ; o i l .

G i u s q u i u n i e t a l . (1995) showed. t h a t t h c m o d i f i c u t i o n r

of s o i l s t r u c t u r e as a consequence of sewage s l u d g e a p p l i c a t i o n

were q u a n t i f i e d th rouch t h e c h a r a c t e r i z a t i o n o f p o r o s i t y and

p o r e s i z e d i s t r i b u t i o n , s i n c e p o r e s de t e rmined t h e most

i m p o r t a n t p h y s i c a l p r o p e r t i e s f o r p l a n t growth. The s t u d y

f u r t h e r r e v e a l e d t h a t p o r e s h a p e , and t h e r e l a t i v e p o s i t i o n

of a g g r e g a t e s were v e r y i m p o r t a n t p a r a m e t e r s u sed i n e v a l u a t i n g

i n d u c e d m o d i f i c a t i o n s of s o i l s t r u c t u r e by sewage s l u d g e

a d d i t i o n s . 'Lhe improvement i n s o i l p h y s i c u l p r o p e r t i e s and .

p a r t i c u l a r l y soil porosity was e q u a l l y found t o r e l a t e t o

i m p a r t m t b ioLog icn1 a c t i v i t i e s buch as t h a t of s o i l enzymes

which were f o u n d t o p o s i t i v e l y c o r r e l a t e with t h e amount of

p o r e s r a n g i n g from 30 t o 200Bm ( ~ a ~ l i a i and DeNob i l i , 1993).

The m i c r o s c o p i c examina t ion o f t h i s s e c t i o n s o f t h e s l u d g e -

t r e a t e d s o i l s amples a c c o r d i n g t o t h e s t u d y , r e v e a l e d t h e

p r e s e n c e of o r g a n i c m a t t e r as w a l l - c o a t i n g s of e l o n g a t e d

p o r e s . The i n c r e a s e i n s o i l p o r o s i t y i n t h e t r e a t e d p l o t s

c o n t r i b u t e d o b v i o u s l y , t o a d e c r e a s e i n b u l k d e n s i t y and a n

i n c r e a s e i n t h e w a t e r r e t e n t i o n capacity of t h e sail.

Metzger and Yaron (1987) observed t h a t the increase i n water

r o t e n t i o n i n sewage t r e a t e d p l a t s was a s c r i b a b l e t o b o t h t h e

Water a d a o r p t i o n c a p a c i t y of o r g a n i c matter and the improvement

of pore ~ y s t e m i n t h e soil, which l e d t o b e t t e r s o i l

s t r u c t u r u l conditions,

S i m i l u r nucceusoo hnve boen reporLed f o r o t h o r o r g a n i c

wastes. For example t h e s t u d i e s of Weil and K r o o n t j e (1979)

on physical c o n d i t i o n s of a Davidson clay loam a f t e r 5 y e a r s

of heavy a p p l i c a t i o n o f p o u l t r y manure, r e v e a l e d a marked

i n f l u e n c e on s o i l s t r u c t u r e i n the plow l a y e r , p a r t i c u l a r l y

at 8 t o 10 cm d e p t h s . Long-term a p p l i c a t i o n of t h e p o u l t r y

manure, a c c o r d i n g t o t h e study, also i n c r e a s e d t o t a l w a t e r -

stable a g g r e ~ a t e s t o n e a r l y 94%- due most e n t i r e l y t o t h e

greater s t a b i l i z a t i o n of a g g r e g a t e s 7 2 mrn i n d i a m e t e r .

E u r l y oi;utiicn, tjuch ua t b o m of' Lcmmermtlnr~ und ljehrenrs

an o r g a n i c wastes re su l t ed i n h i g h e r w a t e r - p e r m e a b i l i t y when

compared w i t h similar u n t r e a t e d p l o t s , and t h a t l e s s water-

logging was obse rved on s l u d g e p l o t s that had been t r e a t e d

f o r t h r e e ~ u c c e s s i ~ e years at r a t e s o f 20 t haw1.

Obi and Ebo (1995) observed a 4 - f o l d i n c r e a s e i n h y d r a u l i c

c o n d u c t i v i t y from 34.8 to 187 mrn hr- I f o l l o w i n g t h e a d d i t i o n

of p o u l t r y manure t o t h e soil.. A r e d u c t i o n i n s o i l b u l k

d e n s i t y from 1.1 t o 0.8 g cmn3 w a s obse rved ( ~ e i l and

K r o o n t j e , 1979) a f t e r 5 y e a r s of a p p l i c a t i o n of p o u l t r y

manure at 110 t ham1 t o t h e s o i l . It w a s a l s o o b s e r v e d t h a t

soil water r e t e n t i o n at t h e m u t r i c p o t . e n t i a l oS -10 KPa

i n c r e a s e d from 32 t o 42% f o l l o w i n g s u c h a p p l i c a t i o n .

The a d d i t i o n s of p i g s l u r r y , sewage s l u d e e and c a t t l e s l u r r y

(Mbagwu and P i c c o l o , 1990) were obcerved t o h a v e i n c r e a s e d

t h e amount o f w a t e r r e t a i n e d at t h e m a t r i c p o t e n t i a l o f

-30 Qa; s i m i l a r l y , s o i l a g g r e g a t e s t a b i l i t y ( d e c r e a s e d

d i s p e r ~ i b i l i t ~ ) i n c r e a s e d by 34, 41 and 26% f o r p i g s l u r r y ,

sewage s l u d g e , a n d c a t t l e s l u r r y - t r e a t e d p l o t s r e s p e c t i v e l y .

Hafez (1974) a l s o obse rved t h a t t h e a p p l i c a t i o n o f o r g a n i c

w a s t e s t o s o i l changed t h e s o i l b i o l o g i c a l , p h y s i c a l , and

c h e n i c a l p r o p e r t i e s , which in turn a c t i v a t e d m i c r o b i a l

b iomass , improv d s o i l s t r u c t u r e , i n c r e a s e d w a t e r - h o l d i n g

c a p a c i t y and a g c r e g a t e s t a b i l i t y .

U n f o r t u n a t e l y , i n a d d i t i o n t o t h e improvemeat of soil

p h y s i c a l c o n d i t i o n s , n number of d e t r i m e n t a l e f f e c t s on s a i l

p h y ~ i c n l p r o p e r t i e s have been obse rved as a consequence of

l ong - t e rm a p p l i c a t i o n of scwugc aludge and e f f l u e n t s t o & o i l s .

O l sen e t a l . (1970) obse rved t h a t s h o r t - t e r m , l ow a p p l i c a t i o n

o f sewage e f f l u e n t s t o s o i l y i e l d e d p o s i t i v e improvement

i n t h e s o i l p h y s i c a l p r ~ p e r t i e s but l a r g e a p p l i c a t i o n s of

s u c h w a s t e s o v e r a l o n g p e r i o d of time r e s u l t e d i n t h e

d e t e r i o r a t i o n o f s o i l p h y s i c a l c o n d i t i o n s . Lieffering and

McLay (1996) obse rved t h a t s o i l a g g r e g a t e s t a b i l i t y can b e

s i g n i f i c a n t l y reduced by t h e a p p l i c a t i o n of h i g h pH o r g a n i c

w a s t e s s u c h as sewage s l u d g e and e f f l u e n t s t o soil. The

r e d u c t i o n i n a g g r e g a t e s t a b i l i t y was a t t r i b u t a b l e t o t h e

d i s s o l u t i o n o f o r g a n i c m a t t e r by t h e h i g h pH solution which

r e s u l t e d i n a l o s s o f i n t e r p a r t i c l e bonding.

O t h e r r e s u l t s ( ~ a l k s e t a l . , 1996) showed t h a t an

i n c r e a f i e i n ~ x c h a n g e a b l e sodium p e r c e n t a g e (ESP) f rom 2 t o

25% a f t e r 5 s e a s o n s of i r r i g a t i o n w i t h sewage e f f l u e n t s

caused an i n c r e a s e i n t h e t endency of t h e s o i l t o d i s p e r s e ,

which r e s u l t e d i n a d e c r e a s e i n s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y .

Sumner a n d McLaughlam (7996) a l s o obae rved r e d u c t i o n i n oil

aggregate s t a b i l i t y as a r e s u l t o f a h i g h c o n c e n t r a t i o n o f

sodfurn i n s oil^ t r e a t e d w i t h sewage. .The r e d u c t i o n i n s o i l

agfpegate s t a b i l i t y decreased i n f i l t r u t i o n ra te and i n c r e a s e d

the r i u k of r u n o f f . The ntudy f u r t h e r ~ h o w e d t h a t high salt

c o n c e n t r a t i o n i n s o i l s o l u t i o n a l s o r e d u c e d t h e s o i l o smot i c

w a t e r p o t e n t i a l s n d t h u s d e c r e a s e d t h e amount o f w a t e r t h a t

was r e a d i l y a v a i l a b l e Xor p l a n t up take . Appl i ca t ion of such

sewage s l u d g e t o heavy s o i l s l e d also t o l o w p e r m e a b i l i t y ,

S i m i l a r s t u d i e s showed t h a t c o i l p e r m e a b i l i t y was r educed

by 95% w i t h i n 2 y e a r s of applying a e w a ~ e e f f l u e n t s . %'he

r e d u c t i o n s i n i n f i l t r a t i o n rate were a t t r i b u t e d t o t h e

accumula t ion o f s o l i d s f i l t e r e d from t h e e f f l u e n t s and/or the

col lapse o f s o i l s t r u c t u r e due t o o r g u n i c m u t t e r d i s s o l u t i o n .

'i'hc r u d u c t i a n i n i n f i l t r a t i o n was o b s e r v e d t o c a u s e pond ing

of t h e e f f l u e n t s t o o c c u r w i t h t h e consequen t increase i n t h e

odour from t h e e f f l u e n t s d i s p o s q l a r e a . T h e r e was a l s o an

i n c r e a s e d r i s k of s u r f a c e r u n o f f which c o u l d c a u s e c o n t a m i n a t i o n

of a d j a c e n t r i v e r s and l a k e s ( ~ u m n e r and :.;i4cLaughlan, 1996).

Appl i ca Lion of sewage e f f l u e n t s to' very l i g h t sandy

s o i l s r e s u l t e d i n c o n t a m i n a t i o n a f ground-water , whereas

a p p l i c a t i o n t o heavy s o i l s , l ow i n p e r m e a b i l i t y and i n f i l t r a t i o n ,

m o u l t e d i n excess r u n o f f C x p s t e i n , 1975). The s t u d y f u r t h e r

showed t h a t s a l t s and o r g a n i c cmnpounds were harmful t o

s o i l s t r u c t u r e . D i s s o l v e d sa l t s , p a r t i c u l a r l y sodium,

d i s p l a c e d calcium, d i s p e r s e d s o i l a g g r e g a t e s , d e s t r o y e d s o i l

s t r u c t u r e , und r educed w a t e r p e r m e a b i l i t y . Also h i g h

c o n c e n t r a t i o n of o r g a n i c s i n e f f l u e n t s a p p l i e d a t h i g h r a t e s

cou ld c l o g s o i l p o r e s and s e a l t h e s o i l s u r f a c e , t h u s r e d u c i n g

i n f i l t r a t i o n r h t e and p e r m e a b i l i t y .

O t h e r t y p e s of o r g a n i c wao te s th:gn sewage s l u d g e and

e f f l u e n t s have also been shown , t o c a u s e u n d e s i r a b l e c o n s e q u e n c i e s

t o s o i l p h y s i c a l properties when l a r g e amounts were a p p l i e d '

o v e r a l o n g p e r i o d of time. F o r example, Tiarks e t al. (1974)

obse rved t h a t s u r f a c e c r u s t i n g , c l o d d i n e s s , i n c r e a e e d s o i l

de tachment by r a i n d r o p s , d e c r e a s e d hydraulic c o n d u c t i v i t y

due t o s o i l d i s p e r s i o n by monovalent i o n s , and f o r m a t i o n of

water - r e p e l l e n t waxy subs tances which r educed f i e l d m o i s t u r e

r e t e n t i o n c a p a c i t y were a s s o c i a t e d w i t h heavy a p p l i c a t i o n of

manure from c a t t l e feed l o t s .

The i m p o r t a n c e of d i s p e r s i b l e c l a y , as a measure o f soil

s t r u c t u r a l i n t e g r i t y , h a s bedn emphasized ( B r u b a k r r e t el.,

a g ~ r e g a t e breakdown (PO jabok a n d Kay, 7990). Hence s o i l . .

'aggregate breakdown and s u b s e q u e n t c l a y d i s p e r s i o n lead t o p o r e

b l o c k a g e and s u r f a c e c r u s t i n g which have i m p l i c a t i o n s f o r

w a t e r i n f i l t r a t i o n and r e t e n t i o n , and s o i l e r o s i o n .

2.2 E f f e c t s o f S e w a ~ e S ludge and E f f l u e n t s on S o i l Chemical

P r o p e r t i e s

In t h e past, t h e limiting c a p a c i t y of t h e s o i l t o sewage

s l u d g e and e f f l u e n t s a p p l i c a t i o n w a s n o t w i d e l y r e c o g n i z e d

but more r e c e n t l y , tire t r o a t m e n t rcr ;ponae ol' n o i l huo gu incd

w i d c r r e c o g n i t i o n . 'I'hc o b j e c t i v e o f l a n d t r e a t m e n t w i t h

sewage s l u d g e and e f f l u e n t s i s t o u t i l i z e t h e c h e m i c a l ,

p h y s i c a l , and b i o l o g i c a l p r o p e r t i e s o f t h e s o i l / p l a n t sys t em

t o a s ~ i m i l a t e t h e waste components w i t h o u t a d v e r s e l y a f f e c t i n g

s o i l q u a l i t y and c a u s i n g c o n t a m j n a n t s t o b e r e l e a s e d i n t o

w a t e r o r t h e atmofiphere,

Cc~ lcn reouc soilr; (Lance , 1977) hnve been o b s e r v e d as

p a r t i c u l a r l y s u i t a b l e for sewage d i s p o s a l because of t h e i r .

a b i l i t y t o s o r b P and t h u s r e d u c e t h e r i s k o f l e a c h i n g i n t o

ground wntcr, but t h u t t h o c apac i t y of c a l c a r e o u s s o i l s t o

s o r b P was l i m i t e d by a c i d p r o d u c t i o n d u r i n g n i t r i f i c a t i o n

o f was t e -de r ived N M ~ + which i n turn r e s u l t e d i n t h e d i s s o l u t i o n

of s o i l c a r b o n a t e and c o n s e q u e n t l y t h e r e l e a s e o f p r e v i o u s l y .

s o r b e d P.

High CEC o r g a n i c s o i l s have been obse rved as good

a p p l i c a t i o n s i t e s f o r sewage s l u d g e and e f f l u e n t s . C u r r e n t

g u i d e l i n e s ( ~ e e n e ~ e t a l a , 1975) s e t heavy m e t a l l i m i t s b a sed

o n s o i l pH and c a t i o n exchange c a p a c i t y (cEC). S t u d i e s have

shown t h a t heavy m e t a l a v a i l a b i l i t y w a E r e l a t e d t o t h e s o i l

CEC and o r g a n i c matter c o n t e n t ( ~ o b e s t s o n e t a l . , 19821, w h i l e

a n o t h e r work h u ~ shown CEC to be a poor p r e d i c t i o n of heavy

m e t a l a v a i l a b i l i t y (Dowdy and Volk, 1984) s t r e s s i n g t h a t

a l t h o u g h heavy metal a v a i l a b i l i t y w a s r educed by h i g h organic

m a t t e r c o n t e n t , e x t e n s i v e l e a c h i n g o f m i n e r a l a o c c u r r e d

where d i ~ p o s a l r a t e s o f sewage s l u d f f e were excessive a n d t h e

s o i l s were c o a r s e - t e x t u r e d w i t h low c o n c e n t r a t i o n s o f h y d r o u s

ox ides .

With r e s p e c t t o t h e improvement o f s o i l f e r t i l s t y , many

s t u d i e s have shown t h a t s o i l f e r t i l i t y i n c r e a s e d a f t e r l a n d

a p p l i c a t i o n of EewaEc s l u d g e and e f f l u e n t s (Keeley and Quin,

1979; Hurt and S p e i r , 1992). F o r example, s t u d y on t h e

e f f e c t s of o v e r 80 y e a r s o f a p p l i c a t i o n of sewuge e f f l u e n t s

t o l i m o r e s i l t loam s o i l i n C a n t e r b u r y , New Zea land ( H a r t and

S p e i r , 1992) showed c o n s i d e r a b l e i n c r e a s e i n s o i l N, P, K, S ,

Ca, Mg, organic c a r b o n , pH, and base s a t u r a t i o n . Shor t - t e rm

s t u d i e s ( B e r n a l e t a l , , 1992) a l s o showed s i g n i f i c a n t i n c r e a s e

i n s o i l N , P , K , and micro n u t r i e n t c o n c e n t r a t i o n s , 8 months

a f t e r a p p l i c a t i o n of s l u d g e t o a c a l c a r e o u s s o i l i n Spain .

Augers and N'Uayegamiye (1991) obse rved t h a t o r g a n i c ca rbon

c o n t e n t of a sandy loam s o i l i n c r e a s e d f rom I .S% t o 2'2%

a f t e r 7 y e a r s o f a p p l y i n g sewage sludge at t h e ra te of 5 t ha-1

1 year- . kn i n c r e a s e i n soil o r g a n i c m a t t e r c o n t e n t r e s u l t i n g from

t h e a p p l i c a t i o n o f sewage s l u d g e and e f f l u e n t s can p roduce a

c o n c o m i t a n t i n c r e a s e i n s o i l c a t i o n exchange c a p a c i t y .

B e r n a l e t a l . , ( l 9 g % ) o b s e r v e d t h a t t h e a p p l i c a t i o n o f sewage

was t e -wa tc r a t r a t e s f rom 200 t o 7000 rn3 ha-I year -1 r e s u l t e d .

i n s i g n i f i c a n t i n c r e a s e s i n s o i l o r g a n i c ca rbon and c a t i o n

exchange c a p a c i t y . S i m i l a r l y , S tade lmann a n d F u r r e r (1985)

o b s e r v e d t h a t 7 y e a r s o f a p p l i c a t i o n o f sewage s l u d g e a t

5 t hao1 ycu ro l t o a anndy 1 0 i ~ m o o i l i n c r c u c c d t h o CliC from

172 Cmol kgm1 i n t h e c o n t r o l p l o t s t o 23.7 a n d 22.2 Cmol kgg1

i n t l ~ u LruuLttd p l o l t i , roupoc Llvoly . S.I gr~lL ' icc i r~ t I~IcI'L'u(.;~ i n

base s a t u r u t i o n was a l s o o b s e r v e d f o l l o w i n g a p p l i c a t i o n of

s e w u ~ e s l u d g e t h a t c o n t a i n e d s i g n i f i c a n t q u a n t i t i e s o f t h e

e x c h a n g e a b l e c a t i o n s , Ca++, ~ g + + , ~a', and K+. However,

G i u s q u i a n i e t a l . (1995) o b s e r v e d t h a t t hough CEC i n c r e a s e d

s i g n i f i c a n t l y i n sewage t r e a t e d s o i l s , i t w a s l o w e r t h a n

e x p e c t e d . T h i s was most l i k e l y due t o t h e f a c t t h a t t h e

t r a n s i t i o n m e t a l s added t o t h e s o i l c o u l d have been complexed,

t h u s c a u s i n g a d e c r e a s e i n t h e n e g a t i v e s u r f a c e c h a r g e o f t h e

o r g a n i c m a t t e r .

S i g n i f i c a n t i n c r e a s e i n s o i l n i t r o g n h a s a l s o been

o b s e r v e d a s a r e s u l t o f l a n d a p p l i c a t i o n o f sewage s l u d g e and

e f f l u e n t s . S t u d i e s by K e l l i n g e t a l . ( 1977) on t h e changes

w i t h t i m e i n t h e c o n c e n t r a t i o n o f s o i l o r g a n i c N , i n o r g a n i c

N, and a v a i l a b l e P i n t h e s o i l p r o f i l e of two s i t e s t r e a t e d

w i t h l i q u i d , d i g e s t e d s l u d ~ e showed t h a t a p p l i c a t i o n o f l a r g e

amounts o f l i q u i d , a g e s t e d sewage s l u d g e i n c r e a s e d t h e

c o n c e n t r a t i o n o f i n o r g a n i c N , o r g a n i c N, and a v a i l a b l e P i n

a sandy loam and a s i l t y loam s o i l i n Sou th -Cen t r a l Wiscons in .

IIowevcr, s u b s t a n t i a l l o s s e s o f s l u d g e - a p p l i e d N were

o b s c r v e d t o o c c u r by leachin[ ; , d e n i t r i f i c a t i o n , v o l a t i l i z a t i o n

o r u combindt ion 01' t h e b e .

IDagwu and P i c c o l o (1990) o b s e r v e d t h a t t h e a p p l i c a t i o n

of sewace s l u d g e at t h e r a t e of 200 t 'ha-' i n c r e a s e d t h e t o t a l

N a n d a v a i l a b l e P c o n t e n t of t h e s o i l by 57% and 64256,

r e s p e c t i v e l y , w h i l s t a p p l i c a t i o n o f o t h e r t y p e s o f o r g a n i c

w a s t e s s u c h as p i g a l u r r y ( 4 0 t ha-') and c a t t l e s l u r r y

( 8 t hao1) i n c r e a s e d t h e s o i l N c o n t e n t by 18 and 13% and

a v a i l a b l e P c o n t e n t by 430 and 3725, r e s p e c t i v e l y . Ross e t al.

(1982) a l s o obse rved t h a t a p p l i c a t i o n of u n t r e a t e d meat

proceo: : ing e f f l u e n t s o v e r a p c r i o d o f o v e r 80 y e a r s (1899-1982)

m i n e r a l i z e d N , a n d a v a i l a b l e P.

Il igh N c o n t e n t i n most sewage s l u d g e and c f f l u e n t s can

c a u s e a d e c l i n e i n s o i l and p l a n t c o n c e n t r a t i o n of K o v e r a

p c r i o d o f t ime. F o r exilmple, Pi l lazzo a n d J e n k i n s (1979)

o b s e r v e d a d e c l i n e i n p l a n t and s o i l c o n c e n t r a t i o n of K o v e r

a 4-year p e r i o d o f l a n d a p p l i c a t i o n o f sewage was t e -wa te r a t

t h e s i t e of t r e a t m e n t , and r e l a t e d i t t o t h e K:N r a t i o of

t h e sewage was te-water a p p l i e d because t h e sewage was t e -wa te r

c o n t a i n e d more t h a n t w i c e as much N as K.

With r e s p e c t t o t h e movement o f P w i t h s o i l d e p t h , Bond e t

(1395) o b s e r v e d no i n c r e a s e i n P c o n c e n t r a t i o n of s o i l w a t e r

a t a d e p t h of 1 .2 m i n a cropped c l a y loam s o i l r e c e i v i n g 5 cm,

of e f f l u e n t s p e r week f o r 8 y e a r s . he P c o n c e n t r a t i o n o f

t h e e f f l u e n t r anged from 4.1 t o 9.7 ppm w h i l e t h e P c o n c e n t r a -

t i o n of t h e soil w a t e r a t t h e 1.2 rn d e p t h w a s less than

0.70 ppm.

In a d d i t i o n t o t h e b e n e f i c i a l e f f e c t s o f l a n d d i s p o s a l

of sewage s l u d g e on t h e s o i l chemica l p r o p e r t i e s , a number o f

d e t r i m c n t u l e f f e c t & and r i s k s a s c o c i u t c d w i t h t h e agronomic

u t i l . i z u t i . o n o f ot .wt~ l~ ;c t;ludt;e i ~ r l d t.fL'Iui~ntt; h u v o boon h i ~ h -

l i c h t e d by Surnner and McLaughlan (1996) a n d Cnmeran e t d. ( 7 9 3 6 ) .

Such d e t r i m e n t a l e f f e c t s and /o r r i s k s i n c l u d e i n c r e a s e d

c o n c e n t r a t i n of d i s s o l v e d P i n r u n o f f , b u i l d - u p of heavy

m e t a l s , n i t r a t e l e a c h i n g t o ground w a t e r , s a l t c o n c e n t r a t i o n

and e l e v a t e d o r ex t r eme ly low pH.

S t u d i e s o f Sabey e t al. (1977) on t h e i n f l u e n c e of sewage

sludge and wood w a s t e m i x t u r e s application on land indicated

that a good combina t ion and p r o p e r managenlent of the m i x t u r e

w a s a v a l u a b l e r e s o u r c e that governed n i t r h t e s u p p l y ,

c o n t r o l l e d n i t r a t e l e n c h i n g and enhanced p h y s i c a l and chemica l

p r o p e r t i e s o f t h e s o i l . But Agbim e t al. (1977) observed t h a t

a p p l i c a t i o n of sewage sludge alone t o t h e soil resulted i n

i n e f f i c i e n t u t i l i z n t i o n o f s o i l . n i t r o g e n by p l n n t s and/or

t o x i c i t y due t o h igh salt c o n t e n t on micro-organisms.

Ifowever, m e t a l t o x i c i t y a c c o r d i n g t o L i e f f e r i n g and McLay

(1996) was a l l e v i a t e d by l i m i n g t h e s o i l ; moreover , c o n t i n u e d

c r o p p r o d u c t i o n r e q u i r e d a n e a r - n e u t r a l s o i l pH; even y e a r s

u f t e r t i l u d g e uppl i .cn t i o n wuti t l i l ;cont i r iut ,d , i n o r d e r t o r f sduce

m o b i l i t y o f heavy m e t a l s t h a t were added t o t h e s o i l .

S i g n i f i c a n t i r i c r e a s e s i n s o i l pH and e l e v a t e d s a l t

c o n c e n t r a t i o n have been obse rved i n s o i l s when seconda ry -

t r e a t e d sewage e f f l u e n t s w i t h a h i g h sodium a d s o r p t i o n r a t i o

(SAR) w a s a p p l i e d ( ~ u m n e r and McLaughlan, 1996) . Johns and

McConchie (1994) obse rved t h a t t h e a p p l i c d t i o n of s econda ry -

t r e a t e d d i l u t e sewage e f f l u e n t s t o s o i l growing bananas a t

~ 6 o l g o o 3 a more t h a n doubled t h e m i l sodium c o n c e n t r a t i o n

from 0.71 t o 0.31 Crnol kg-1. Despite t h e l o w e l e c t r i c a l

c o n d u c t i v i t y of t h e e f f l u e n t (0.44 d s m b l 1, t h e oil exchangcnb le

sodium p c r c e n t u g e (ESP) v a l u e s reached 4% during t h e t r ia l ,

S i m i l a r l y , l a n d d i ~ p o r d of t r e a t e d sewage e f f l u e n t s t o

a Waimakar i r i lsandy l a a m i n C a n t e r b u r y , New Zealand s i g n i f i -

c a n t l y i n c r e a s e d s o i l salinity. The e l e c t r i c a l c o n d u c t i v i t y .

of t h e s o i l i n c r e a s e d f rom 0.4 mm hos cm*' t o 5.5 mrn h o s ~rn- ' ;

r educed growth and y i e l d s o f many crops were o b s e r v e d

(Balks e t al., 1996) . A h i g h concentration of N a i n s o i l s i s

of conce rn because i t can c a u s e a r e d u c t i o n i n s a i l a g g r e g a t e

stability. T h i s can cause a d e c r e a s e i n i n f i l t r a t i o n rate ,

and un i n c r e a s e i n t h e r i s k o f r u n o f f .

High c o n c e n t r a t i o n s of boron, sodium, c h l o r i d e , carbonutcs,

and t o t a l d i s s o l v e d s o l i d s i n sewage w a s t e waters could damage

p l a n t s because t h e advantageous u s e o f e f f l u e n t s on l a n d

depends on t h e q u a l i t y of waste water, soil t y p e , crop , and

c l i m a t e . Crops v a r y i n t h e i r t o l e r a n c e t o salts.

F o r e x a m p b , B a l k s e t a l . (1996) obse rved t h a t b e a n s , r e d

c l o v e r , g roundnut and c i t r u s were more s e n s i t i v e t o s a l t s

and o r g a n i c cornpounds aszoci&ited w i t h sewage was t e -wa te r t h a n

g r a s s e s , b a r l e y , and c o t t o n .

Ihgh c o n c e n t r a t i o n of ~a' and Cl- was a180 o b s e r v e d i n

Llic t o p 15 cnl 01' s o i l s tro:lt t?d with hcof focrll.oL cffl.uc:ntn

('i ' inrlcs e t a l . , 1974) . The major f a c t o r r e s p o n s i b l e f o r t h a t

+ development , a c c o r d i n g t o t h e s t u d y , w a s t h e h i g h N a c o n t e n t

o f t h e f e e d l o t e f f l u e n t s . The a p p l i c a t i o n t o s o i l o f e f f l u e n t s

f rom a p u l p and p a p e r m i l l i n IJew Zea land , i n c r e a s e d t h e

sodium a d s o r p t i o n r a t i o ( S A L ~ ) from 2 t o 16 and i n c r e a s e d

sodium c o n c e n t r a t i o n i n ground w a t e r (Johnson and Ryder , 1988).

Brech in and McDonald (19941 a l s o d e t e c t e d a n i n c r e a s e d sodium

c o n t e n t i n c o i l f e r t i l i z e d w i t h p i g s l u r r y i n Sou th A u s t r a l i a .

and s u g g e s t e d that t h i s c o u l d become a problem i n t h e long- te rm.

2.3 Heavy N e t nls i n Sewage Slud~e- 'P re t c t ed Soils

Heavy m e t a l s a r e p r e s e n t i n a number o f w a s t e s t h a t are

a p p l i e d t o t h e l a n d . Sewage s l u d g e and effluents are the

majo r s o u r c e b u t o t h e r w a s t e s such as tannery e f f l u e n t s , p u l p

and p a p e r sludges, l a n d f i l l l e a c h a t e , and p i g s l u r r y a l s o

c o n t r i b u t e t o heavy m e t a l accumula t ion i n t h e soil. S o i l

p r o p e r t i e s such as pH, r edox p o t en t i a l , m i n e r a l o g y , t e x t u r e ,

c a t i o n exchange c a p a c i t y (CEC), and o r g a n i c m a t t e r c o n t e n t

have been obse rved t o a f f e c t heavy m e t a l s o l u b i l i t i e s and

s u b s e q u e n t c rop u p t a k e (Chancy, 1994) .

D i s p o s a l on s o i l s w i t h l o w e r pH o f sewage sludge and

e f f l u e n t s w i t h h i g h e r heavy m e t a l bu rdens might r e s u l t i n

n u t r i t i o n a l i m b a l a n c e s , p h y t o t o x i c s i t u a t i o n s , and reduced

c r o p p r o d u c t i o n . The c u m u l a t i v e amount of sewage s l u d g e

tha t can b e a p p l i e d t o a s p e c i f i c s i t e i s u s u a l l y de t e rmined

-by t h e amount o f heavy m e t a l s a p p l i e d v i a t h e s l u d g e .

Cont inued a p p l i c a t i o n o f s l u d g e at h i g h r a t e s was o b s e r v e d

t o b u i l d up c o n c e n t r a t i o n s o f heavy m e t a l s t o harmful l e v e l s

i n t h e r e c i e v i n g s o i l s , a l t h o u g h t h e r e w a s e v i d e n c e from

Europe t h a t heavy m e t a l c o n t e n t of t h e s o i l r e c e i v i n g s l u d g e

o v e r a 60 y c n r s p e r i o d s i g n i f i c a n t l y d e c r e a s e d a f t e r

a p p l i c a t i o n h a s ceased f o r 18 y e a r s (L'~ Hermi te and O t t , 1981 1.

H i n e s l e y e t a l . (1972) o b s e r v e d t h a t t h e maximum

c u m u l a t i v e a p p l i c a t i o n o f s ludge -borne Zn and Cd w a s l i m i t e d

t o 500 kg ha-' and 10 kg ha-' r e s p e c t i v e l y f o r s o i l s h a v i n g

c a t i o n exchange c a p a c i t i e s r a n g i n g from 5 t o 15 Cmol kg-'

s o i l . A c c e p t a b l e m e t a l l o a d i n g r a t e s - w e r e doub led f o r s o i l s

huvinp: CEC in excess of 15 Crnol kgo1 c o i l .

LOSS of s o i l p r o d u c t i v i t y and /o r f o o d c h a i n t o x i c i t y

can b e gua rded a g a i n s t i f r e s t r i c t i o n s a s s o c i a t e d w i t h the

a p p l i c a t i o n o f sewage s l u d g e and e f f l u e n t s t o l a n d are observed.

Some o f t h e heavy m e t a l s , such as Cu a n d Zn, a r e e s s e n t i a l

p l a n t n u t r i e n t s , and a d d i t i o n of sewage 61-udge and e f f l u e n t s

t o l ow f e r t i l i t y s o i l s may i n f a c t p r o v i d e b e n e f i c i a l

q u a n t i t i e s of t h e s e m e t a l s which a r e no rma l ly i n s h o r t supp ly .

N o t w i t h s t a n d i n g , a t h i g h c o n c e n t r a t i o n s , heavy m e t a l s have

Lecn o b s e r v e d to be phytdtox ic und rcnu1, ted i n r e d u c e d p l a n t

growth a n d / o r enhanced m e t a l c o n c e n t r a t i o n s i n p l a n t , e s p e c i a l > y i n l o w pH soils ( ~ h i x t c y , 1994). E x c e s s i v e and/or

r c p e a t c d a p p l i c n t i o n s of m e t u l b e a r i n g matcririls t o t h a s o i l

i n wha teve r form have t h e p o t e n t i a l o f r e s t r i c t i n g p l a n t growth

and r e d u c i n g c r o p y i e l d s . U l t i m a t e l y , yrcld r e d u c t i o n h a s

been t h e most important measure of p h y t o t a x i c i t y for agronomic

s p ~ r c i e s , s i n c e i t affects t h e p r o f i t a b i l i t y o f c r o p p r o d u c t i o n

and l i m i t s t h e u t i l i t y a f t h e l and .

It has been dernonstra t e d t h a t e l e v a t e d metal c o n c e n t r a t i o ~ ~ c

can r e d u c e s o i l microbial b iomass l e v e l s , i n h i b i t N 2 - f i x a t i o n

by b o t h f r e e - l i v i n g a n d s y m b i o t i c o rgan i sms , and r e d u c e

c e r t a i n enzyme a c t i v i t i c s CNcCruth, $9311 1. S i n c e ' t i o i l micro-

or[pnicmc and t h e i r a c t i v i t i e s a r e c r u c i a l t o t h c ma in t enance

of 6oiL f e r t i l i t y , t h e r e i f i c o n s i d e r u b l e concorm t h a t rnotal

a d d i t i o n s cou ld have permanent ndve rae e f f e c t s on s o i l q u a l i t y .

U n f o r t u n a t e l y , t h e r e hc.m been much c o n t r a d i c t o r y e v i d e n c e

r e l a t i n g t o t h e e f f e c t s of m e t a l s on s o i l b i o l o g i c a l a c t i v i t y ,

p a r t i o u l a r l y when the mstn1.s woro p r ~ a a n t in sewage s ludge

and e f f l u e n t s (Smi th , 1391). Nevertheless, t h e r e is no doubt

t h a t when large q u a n t i t i e s o f m e t a l s a r e added t o s o i l as

o r g 3 n i c salts, t o x i c e f f e c t s o n s o i l o rgan i sms and b i o l o g i c n l

processes a r e obse rved .

I n v e s t i g a t i o n s by a number of worke r s on t h e movement of

m c t d s in s o i l s t e n d t o ehow t h a t m e t a l s added t o t h e s o i l i n

wastes, p a r t i c u l a r l y i n sewage s l u d g e , accumula t e an o r v e r y

n e a r t o t h e : j ~ r f a c e l a y e r s o f t h e s o i l . The re appears t o

b e l i t t l e movement o f heavy m e t a l s be low t h e zone o f

i n c o r p o r a t i o n o f t h e sewaKe s l u d g e . Dowdy and Volk [19845 i n

an e x t e n s i v e r ev i ew of heavy m e t a l movement I n s e w a g e d t r e a t e d

s o i l s , conc luded t h a t movement mast l i k e l y o c c u r r e d where

heavy a p p l i c a t i o n s of sewage s l u d g e and e f f l u e n t s were made

t o s a n d y , a c i d i c , low o r g a n i c m n t t e r s o i l s receiving h i g h

r a i n f d l or irrjgation, Smith (7997) showed e v i d e n c e of s u c h

movement i n a sandy s o i l t r e a t e d wi th . sewage s l u d g e a t

i n t e r v a l s o v e r a p e r i o d o f 25 y e a r s .

Anderson and Nileson (1972) obse rved that a f t e r 12-year

appl icnLi .on or 84 t t lu- I DL' eeua,:u n l u c l ~ ~ v t o t . i o l l ~ , p r u c t i c o l l y

d l t h e Mn, Ln, Cu, N i , Crr, P b , Cd, He;, A s , and S c ~ernuined

i n t h e s u r f a c e 20 crn of t h e s o i l . H i n e s l e y e t a l . (1972)

on the o t h e r hand, obse rved t h a t m e t a l s had moved 1 5 cm deep

i n t i ~ a s o i l f o l l o w i n g a 3-year a p p l i c a t i o n of 166 t ha-' of

sewaKe. S i d l e a n d Sopper (1376) a n a l y s e d s o i l s a f t e r a n 11-

year a p p l i c i i t i o n o f sewage e f f l u e n t s and s l u d g e and found no

m~vctnont o f C d beyond t h e 0-15 cm d e p t h . In a f i i rn i la r study

(dideraon a n d N i l e s o n , 19721, i t was o b s e r v e d t h a t t h e ma jo r

accumula t ion o f m e t a l s o c c u r r e d i n t h e u p p e r 6 cm o f a sandy

s o i l t h a t h a s been t r e a t e d f o r 33 y e a r s w i t h s e c o n d a r y

e f f l u e n t s . Cameron e t al. (1996) a l s o chowed t h a t t h e meen

i n c r e a s e s i n c o n c e n t r a t i o n o f a number o f heaGy m e t a l s i n t h e

-1 soil f o r e a c h t o n o f s l u d g e added were 0,38 mg kg (:!0.04)

f o r Pb, 0.21 rng kgg1 (+_ 0.06) f o r Zn, 0.157 rng kg'l (2 0.04).

accurnul:~ t i 0 1 1 : 1 r 1 1 l po:,::i t) l P p t ~ y t o t o x i c j t y rtrr. L)~ i l rnSdre , t h o

m o ~ t c r i t i c a l l o n e term huzardzi when upply in [ : t?cwuKe s l u d g e

and e f f l u e n t s t o l a n d .

2.4 P a t h o c c n s

I n d i c a t o r o rgan i sms s u c h as t o t a l e o l i f o r m s , f e c a l

c o l i f o n n s , a n d f e c a l s t r e p t o c o c c i 11uve r r e q u e n t l y b e e n u s e d

t o a s s e s s t h e p o t e n t i a l s f o r d i s e a s e t ransrnis ; ion from sewage

e f f l u e n t s . F e c a l co l i fo r rns are r e p o r t e d t o b e a r e l i a b l e

i n d i c a t o r of f e c a l p o l l u t i o n (Clark and K a b l e r , 19641, and

have o f t c n been u t i l i z e d t o t r a c e t h e rnovr!rncnt of o rgan i sms

from sewage e f f l u e n t s f i e l d s . H e p o r t s of t h e c o n t a m i n a t i o n

o f shal low w e l l s w i t h f e c n l c o l i f o r r n s are common. Clark and

Kuble r (1364) obse rved movement of fecal californla t o a w e l l

a t a d i s t a n c e o f 71 m a f t e r 23 y e a r s of sewage effluents

d i s p o s a l , a l s o a 3-m deep w e l l was contaminated af ter o n l y

10 d a y s o f l a n d . d i s p o s a l of sewage e f f l u e n t s .

Reduc t ion i n the number of i n d i c a t o r o r g a n i s m s , f o r

example, f e c a l c o l i f o r m s , t o l o w e r l e v e l s is o f t e n e i t h e r

r e q u i r e d o r f e l t t o b e h i g h l y d e s i r a b l e i n a w a s t e w a t e r

t r e a t m e n t system. About 600,000 f e c a l c o l i f o r m s p e r 100 ml

were found i n s e c o n d a r y - t r e a t e d sewage e f f l u e n t s i n New Zealand .

..But where t r e a t m e n t p l a n t s had e f f l u e n t s d i s i n f e c t i o n

f a c i l i t i e s , f e c a l c o l i f o r m s were r educed t o about 8000 p e r

100 m l (sNZ, 19931, S i m i l a r l y , t h e a n n u a l mean fecal c o l i f o r m

count i n 1992 was 55000 p e r 100 rn l n e a r t h e Terminal i n t h e

i n n e r h a r b o u r o f Wel l ing ton . Un i t ed S t a t e s Envi ronmenta l

P r o t e c t i o n Agency (USEPA, 1993) s e t a c c e p t a b l e c o u n t s o f f e c a l

c o l i f o r m s at 200 p e r 100 m l i n w a s t e w a t e r a n d conc luded that

i t s u t i l i z a t i o n may n o t be s a f e i f the c o n c e n t r a t i o n e x c e e d s

t h i s l i m i t . /

G e n e r a l l y , i t ha5 beell observed t h a t b a c t e r i a l p a t h o g e n s

s u r v i v e i n s o i l o r w ~ ~ t e r from H f e w duyu t o 5 o r 6 months ,

w i t h some r e p o r t s i n d i c a t i n g s u r v i v a l as l o n g a s 5 y e a r s .

A p p l i c a t i o n o f s e t t l e d sewage t o c a r r o t s , cabbages , and

potatos (Gerba e t a l . , 79753 showed t h a t c o l i f o r m s were

d e t e c t e d in t h e s o i l and on l i v i n g p o t a t o tubcrs a f t e r 40 days,

on c a r r o t s a f t e r 1 0 days, and o n cabbage leuvor;, after 5 d a y s .

h l l i o t and Zllis ( 1 9 7 7 ) ~ i n a r e v i e w of m i c r o b i a l h e a l t h

huzurdu from t h e u:,c o r wastes f o r crop n u t r i e n t s , conc luded

t h a t t h e consumption of raw v e g e t a b l e s i r r i g a t e d w i t h sewage

has c a u s e d o u t b r e a k s o f t y p h o i d and w a r m i n f e c t i o n s and

recommended t h a t , f o r c u r r e n t use on gurden c r o p s , sewage

s h o u l d be sterilized o r f i l t e r e d . S t r a u b et al, (1993) equa1J.y

o b s e r v e d that t h e v a r i o u s species o f p a t h o g e n i c micro-

organ i sms , s u c h as t h o s e causing t y p h o i d f e v e r , b a c c i l a r y

d y s e n t r y , urnoebic d y s e n t r y , n s c a r i a 6 i s , and h c l m i n t h i c

d i s e a s e s , were i s o l a t e d from raw sewage s l u d g e . They f u r t h e r

i n d i c a t e d t h a t when u n t r e a t e d domes t i c sewage s l u d g e was u s e d

t o f e r t i l i z e p l a n t c r o p s , t h e r e w a s a l i k e l i h o o d t h a t raw

food was con tamina ted by human pathogens.

V e g e t a b l e s taken d i r e c t l y from t h e f i e l d were c o n t a m i n a t e d

C a t i o n exchange c a p a c i t y , t e x t u r e , s t r u c t u r e as w e l l a s t h e

l o u d i n g r a t e s of nuwugc ~1udk;o a n d a f f l u n n t ~ h t ~ v e been

abcorved t o g r e a t l y i n r l u e n c o t h e s u r v i v a l a n d e x t e n t o f

movement of p a t h o g e n s i n t h e soil.

In c o n c l u s i o n , i t h a s become a p p a r e n t f rom t h e l i t e r a t u r e

that t h e m a j o r i t y o f research i n t o l a n d t r e a t m e n t o r d i s p o s a l

o f sewage s l u d g e and e f f l u e n t s has been c a r r i e d o u t i n

deve loped countries and p u b l i s h e d o u t s i d e t h e c o r e s o i l

science l i t e r a t u r e ; y e t , t h e l ong - t e rm e f f e c t s o f sewage s l u d g e

and e f f l u e n t s d i s p o s a l o n t o l a n d is e s s e n t i a l l y a s o i l

s c i e n c e problem, which n e e d s l o be s t u d i e d i n d e v e l o p i n g

c o u n l r i a s , boc;~ut;cy i t w i l l r ( ] p r ~ ~ f J l l t one o f t.hn i r r i p o r t ~ ~ n t

a p p r o ~ i c h c s in t h e u n d e r s t u n d i n g of t h e l o n g term prob lems

a s s o c i a t e d with d i s p a s a l o f sewage s l u d g e and e f f l u e n t s i n

Nigeria.

CHAPT EII TBRXE

3.0 ~L'L'LHIALS nNL) MEr1'lfODS

3. I Sit o Uo:;cldp I: ion

The s t u d y was curried o u t a t t h e Un ive r : . i t y o f Nigcria,

Nsulrka, sewage d i s p o s a l s i t e . The s o i l i s c l a s s i f i e d as

Arenic Kundi u s t u l k s (USDA, 19841, d e r i v e d from False-bedded .

Sandstone (Akamigbo and Igwe, 1990a) . The a r e a i s l o c a t e d

w i t h i n l a t i t u d e ObQ 51 'N and l o n g i t u d e 07' 2 4 ' E , c h a r a c t e r i z e d

by t r o p i c a l w e t climate u s u a l l y from t h e month of A p r i l t o

Oc tobe r a n d dry climate u s u a l l y from t h e month o f November t o

b r c h , and s e c i e v e ~ mean a n n u a l r a i n f a l l of a b o u t 1700 mm

The s o i l of the s i t e h a s been s u b j e c t e d t o heavy a p p l i c a t i o n s

of p a r t i a l l y t r e a t e d sewage o l u d g e and e f f l u e n t s f o r n o t l e s s

t h a n 36 yearc and thc! farmine; cornmunil;y h a s bocn t a k i n g

advan tage o f the sludge and e f f l u e n t s t o [:row v a r i o u s c r o p s

i n c l u d i n g vegetables (Eze 7998 - P e r s o n a l communicat ion) .

The sewage s ludge and e f f l u e n t s p a s s e d t h r o u g h t h e

"prirnsry" t r e a t m e n t p a t h way. P r imary t r e a t m e n t i n v o l v e s

s e d i m e n t a t i o n of the b i o s o l i d s . S e t t l i n g i s h a s t e n e d by g r a v i t y

and c h c l n i c d flocculation with alumillurn a n d hydrated l i m e

t r e a t m e n t . The sewace d i d n o t pass t h r o u g h f u r t h e r s t a b i l i z a t i o n

i n v o l v e d i n t h e seconda ry and t e r t i a r y t r e a t m e n t pathway.

Hence t h e name " p a r t i a l l y t r e a t e d sewep;e s1udp;e and e f f l u e n t s " .

The s t u d y i n v o l v e d :

(a) F i e l d i n v e s t i g a t i o n s

( b ) Greenhouse s t u d i e s , and

( c ) L u b o r a t o r y s t u d i c s .

3.2 F i e l d T n v e o t i r n t i o n s

This i n v o l v e d a p p r a i s a l s t u d i e s and t h e a c t u a l f i e l d

e x m i n u t i o n of t h e current s t a t e o f knowledge a n d u n d e r s t a n d i n g

of the sewage d i s p o s a l s i t e . Having t a k e n i n t o due

c o n s i d e r a t i o n t h e h e t e r o g e n e i t y i n s o i l t opography o f t h e

s t u d y a r e a , two r e p r e s e n t a t i v e p r o f i l e pits were s i t e d a t

t h e sewage d i s p o s a l s i t e a b o u t 2 m e t r e s away from t h e

o x i d a t i o n pond, and one r e p r e s e n t a t i v e s p r o f i l e p i t , a l s o s i t e d

i n t h e a d j a c e n t l a n d t h a t h a s n o t been a f f e c t e d by t h e s l u d g e

and 6Lf f luen t s d i s p o s a l , abou t 100 m e t r e s Nor th o f t h e sewage

d i s p o s u l s i t c t o form t h e b a s i s f o r t h e compara t ive s t u d y .

D i s t u r b e d and u n d i s t u r b e d s o i l snrriplc: were c o l l e c t e d

froci t h e g e n e t i c h o r i z o n s of t h e p r o f i l e p i t s f o r t h e

d e t e r m i n a t i o n z of t h e s o i l p h y s i c a l and chemica l p r o p e r t i e s . .

The b i o s u l i d s were c o l l e c t e d a t t h e d i s p o s a l end o f t h e sewage

t rea t t i l en t u n i t f o r laboratory analysis and c h a r a c t e r i z a t i o n

u ~ i n g the U n i t e d Sta tes Envi ronmcntn l P r o t e c t i o n Agency

(USEPA, 1393) s t a n d a r d s i n saila ( T a b l e 1) .

T a b l e 1 : Elernentnl C h a r a c t e r i s t i c s o f sewaEe s l u d ~ e --.--A

Organic C

T o t a l N

' l 'otul P

Fecal Co l i fo rm

T o t a l C o l i f o m

a S t a n d a r d s a f t e r USEPA (1993)

b Surnples from t h e s t u d y area.

3.3 Greenhouse S t u d i e s

For t h e g reenhouse s t u d y , bu lked s o i l s amples were

c o l l e c t e d from t h e 0-30 cm d e p t h s of t h e s t u d y s i t e s f o r

comprrrative ur;:~ar;:,rnen t of' t;ho cf f o c t u of lo rq - t e rm d i a p o u e l

of the [rawugn tilutleo untl o f l ' l u e n t t i ur i ink- t h o purforrnuncc~o

of maize (%eu mays L,} and Uumbaru groundnut (viKntr. - subterraneal i n a Completely Randomized Des ign ( C R D ) w i t h

9 r e p l i c a t i o n s . The p o p u l a t i o n w a s 2 maize p l a n t s a n d

2 Bambara groundnut p l a n t s p e r p o t .

When t h e Bambara groundnut i n t h e sewage s o i l d i e d

w i t h m a few weeks o f emergence - a d e a t h s u s p e c t e d t o have

been caused by p h y t o t o x i c i t y , o t h e r s o i l s amples were

c o l l e c t e d from t h e sewage d i s p o s a l s i t e a n d l e a c h e d f o r 2 weeks

b e f o r e t h c second p l a n t i n g o f bambara g roundnu t , Leaching

w a s accompl ished by l e a v i n g t h e h o l e s a t t h e bot tom of t h e

cerarnic p o t s open w h i l e f l o o d i n g t h e s o i l w i t h s u f f i c i e n t

w a t e r , A number o f c h a r a c t e r i s t i c s o f t h e s o i l s u s e d i n

t h e g reenhouse s t u d y a r e r e p o r t e d i n 'I 'ables 2a and b.

Maizc p l a n t h e i z h t was r e c o r d e d weelcly f o r 5 weeks and

t h e d r y m a t t e r y i e l d o b t a i r ~ e d a t t h e end o f 5 weeks. The

b m b a r a g r o u n d n u t s were h a r v e s t e d a t 115 days a f t e r p l a n t i n g .

3.4 L a b o r a t o r y S t u d i e s

P a r t i c l e Size and P o r e S i z e D i s t r i b u t i o n s

P a r t i c l e s i z e d i s t r i b u t i o n was c a r r i e d o u t by t h e

bouyoucos (1951) hydrometer method w i t h aodjum hexametaphosphate

(Ca lgon) as t h e d i s p e r s i n g a g e n t .

T a b l e 2a: Some p h y s i c a l and s a l i n i t y c h a r a c t e r i s t i c s o f t h e ,

t o p 0-30 cm s o i l used i n t h e p e e n h o u s e s tudy .

- Sewage S o i l Non Sewage S o i l

S o i l P r o p e r t y F i r s t Second

P l n n t i n g a P l a n t -

T e x t u r a l c l a s s Sandy lourn Sandy Toam Sandy l o r n

. . Bulk d e n s i t y ( g crn-3) 1.16 - 1.46

Hydrau l i c c o n d u c t i v i t y (ern hr" ) 12a37 - 20 a 91

Sodium a d s o r p t i o n r a t i o (SARI 0.13 0.11 0.10

Exchangeable sodium percentage 2.20 2.00 1.97 .

K L e c t r i c n l c o n d u c t i v i t y (rnrnhos amo4) 2.10 0.89 0.08

S a l t c o n c e n t r a t i o n (rngl-' ) 1344 570 51.2 '

Total c a t i o n c o n c e n t r a t i o n (Me 1") 21 8.90 0.80

o s m o t i c pressure ( a t ~ 1 ) 0.76 0.32 0.03

S a l i n i t y haza rdc Yieldn o f S u l i n i t y S a l i n i t y many c r o p s e f f e c t s effects r e s t r i c t - negligible negligible t ed

i Used i n t h e first p l a n t i n g t o mdize and bambara groundnut

b. Used i n t h e second planting t o bambara groundnut o n l y

c. R a t i n g s a f t e r B e r n s t e i n (1964).

T a b l e 2b: Some chemical characteristics of the t o p 0-30 cm s o i l u s e d i n t h e g r e e n h o u s e s t u d y

Sewage S o i l Non Sewage Soil S o i l pro port.^ F i r ~ j L C c ~ c o n d

Plr i n t i lip: u P l u r i t inITb

pH (H20)

pH ( O * I N K C 1 1

T o t a l Organic Carbon (78

O r g a n i c M a t t e r ($1

T o t a l N i t r o g e n ($1

Exchangeable Nn (Cmol kg-' )

I I 11 I 1

II C a I I

I 1 M G I I

CEC f I

iI;xchangc:.blc A c i d i t y " Base S a t u r a t i on (7:)

Heavy Metals (pprn) - Fe

a. Uscd in t h e f i r s t planting t o maize a n d bambara g r o u n d n u t

b. Uscd i n t h e s e c o n d planting t o bambara g r o u n d n u t o n l y

P 0 r o ~ i i t y and pore-clzc d i s t r i b u t i o n wore c o l c u l a t c d

r i l o t a l p o r o s i t y = volume o f wa te r i n soil at ~ a t u r a t i o n (crn3) volume o f b u l k s o i l

Macro p o r o s i t y = volume o f water. d r a i n e d o u t a t 60 cm tension volume o f b u l k s a i l

Micro p o r o s i t y = volume o f water r e t a i n e d a t 60 cm tension volume of bulk s o i l .

Bulk D e n s i t y and Water Re ten t i -on C a p a c i t y

U n d i s t u r b e d s o i l c o r e s measu r ing 118.8 cm3 were used

f o r t h e d e t e r m i n a t i o n of bulk d e n s i t y and w a t e r r e t e n t i o n

c a p a c i t y . b u l k d e n t ; i t g wu:; c n l c u l etcd itc iiu:icrkbed by O b i (1390).

Water retenti .011 a t 0 , 3 0 , 6 0 , and 100 cm hei1;hts on t e n s i o n

t a b l e s were de t e rmined by t h e h a n g i n g column method as

d e s c r i b e d by R i c h a r d s (7957). The water r e t e n t i o n a t f i e l d '

c a p a c i t y was de te rmined a t 60 cm t e n s i o n .

S a t u r a t e d 1Iydrauli.c C o n d u c t i v i t y

TLe u n d i s t u r b e d soi l . c o r e s amples were u s e d f o r t h e

d e t e r m i n a t i o n of t h e s a t u r a t e d h y d r a u l i c c o n d u c t i v i t y by t h e

c o n s t a n t head pcrmeamcter t e c h n i q u e lute and Di rkson , 1986).

3 i d e n t i c a l c y l i n d e r (118.8 cm ) was a t t a c h e d t o t h e open

end w i t h duc t tape t o a c t as r e s e r v o i r f o r t h e h y d r a u l i c head.

T l ~ c o t h e r end o f t h e assembly w a s cove red w i t h cheese c l o t h

t o retain s o l i d s , a n d placed on a Buchner f u n n e l t o c o l l e c t

leachate. \dater was added t o t h e r e s e r v o i r and f l o w a d j u s t e d

s o as t o m a i n t a i n a c o n s t a n t head o f 3 cm. L e a c h a t e volume

was measured o v e r t i m e p e r i o d s u n t i l f l o w w a s e s s e n t i a l l - y

c o n s t a n t a t w h i c h t i m e , the f i n a l f l o w r a t e was d e t e r m i n e d .

S a t u r a t e d h y d r a u l i c c o n d u c t i v i t y ( K S ) w a s d e t e r m i n e d f r o m ;

where Ks = Saturated h y d r a u l i c c o n d u c t i v i t y (cm h r - I )

3 O = Vol. o f w a t e r (cm )

2 A = C r o s s s e c t i o n a l a r e a o f s a m p l e (cm )

T = Time ( s e c o n d )

L = L e n g t h of core 4cm3

AH = l lydraul ic head Ccm]

A g ~ r e p t c S t a b i l i t y

$ I t ~ w c ~ l t y f i v c . gmm:. of a i r - d r y coil s a m p l e were p laced i n

sample and s i e v e s ( 2 mm, 1 mm, 0.5 mrn, and 0.25 rnm) were

repeatedly ra ised and lowered, w h i l e completely s u b m e r g e d i n

water f o ~ about 30 m i n u t e s . The c o n t e n t s o f each s i e v e were

weighed t o determine t h e f r a c t i o n o f t h e sample t h a t r e m a i n e d

i n each s i eve . The mean w e i g h t d i a m e t e r (MWD) of t h e w a t e r -

s t a b l e a g g r e g a t e was c a l c u l a t e d as:

where IbZJU = Mean w e i g h t d i a m e t e r (mm)

X = bIean d i a m e t e r o f e a c h s i z e f r a c t i o n (mm)

Wi = The p r o p o r t i o n o f t h e t o t a l s a m p l e w e i g h t i n t h e

c o r r e s p o n d i n g size f r a c t i o n

and w a t e r - s t a b l e a g g r e g a t e s (WSA) u s ,

where WSA = P e r c e n t w a t e r s t a b l e a g g r e g a t e s

WR = Mass o f r e s i s t a n t a g g r e g a t e s ( g )

My = The t o t a l mass o f we t - s i eved s o i l (g)

K l e c t r i c a l Conductivity, S a l t C o n c e n t r a t i o n , T o t a l C a t i o n

C o n c e n t r a t i o n and Osmotic P r e s s u r e

E l e c t r i c a l c o n d u c t i v i t y , salt c o n c e n t r a t i o n , t o t a l c a t i o n

c o n c e n t r a t i o n and osmot i c p r e s s u r e were measured i n 1:2.5

0 ( s o i l / w i i t c r ) uqueous e x t r a c t u t 25 C as d e s c r i b c d by b l a c k e t d.

1 9 E l e c t r i c a l conc iuc t iv i ty w a s c i~ lcu l : i t c d u s :

~c(mrnhos cm-I) a t 2 5 ' ~ = 0 . 0 0 1 ~ ~ 1 1 8 x Rext 10QO x - - - ( 4 ) 'std I

where O . O O 1 4 l l 8 = K'lc c t r i c n l c o n d u c t i v i t y o f t h e s t a n d a r d

O.OIN K C 1 s o l u t i o n at 2 5 ' ~

Next = L p e c i f i c c o r ~ d u c t a n c e o f t l l o e x t r a c t ( s an-')

K s t d = S p e c i f i c conduc tance o f t h e s t i n d a r d (6 cui-')

Sal t c o n c e n t r a t i o n r n 1 = 640 x E l e c t r i c a l c o n d u c t i v i t y (mahos

Total c a t i o n c o n c e n t r a t i o n = 10 x E l e c t r i c a l c o n d u c t i v i t y (mmhos c

Osmotic p r e s s u r e ( a h ) = 0.36 x E l e c t r i c a l c o n d u c t i v i t y (mmhos cm'

S a l i n i t y hazards were c l a s s i f i e d a c c o r d i n g t o U e r n s t e i n (1964)

as shown i n T a b l e 3 .

Tab le 3 : C l a s s i f i c u t i a n of e l e c t r i c a l c o n d u c t i v i t y ( E G ~ ) at 250C and s a l i n i t y ' ~ l a z n r d s

Toted D i s s o l v ~ d h l e c t r i c a l Conductivity S a l i n i t y Hazards S o l i d s (mg 1 - I ) (rnmhos c m - l )

s a l i n i t y e f f e c t s n e g l i g i b l e

Y i e l d s o f v e r y s e n s i t i v e c r o p s may be r e s t r i c t e d '

Y i e l d s o f many c r o p s r e s t r - i c t c d

Only tolerant crops y i e l d s a t i s f a c t o r i l y

Only a few very tolerant crups y i e l d sa t ia fac tor i ly

After Bernetein (1964)

S o i l pH

The s o i l pH i n w a t e r a n d in O . I N KC1 w a s measured w i t h

a glass e l e c t r o d e u s i n g a 1:2.5 c o i l / w a t c r and s o i l / ~ . l ~ K C 1

aqueous s o l u t i o n ( McLenn , 1982).

T o t d Organ ic Carbon and N i t r o g e n

i 1 l a t a l url::rtlic carbon was d e t e r n i n e d by t h e Walkley and

illaclc wet d i c h r o n ~ u t c o x j - d a t i o n method w i t h l12SQ4 - K2Cr207 fo l lowed by residual t i t r a t i o n of ~r07-' with I N HC1 (Ne l son

a d So~nmer, 1982). l ' o t a l n i t r o g e n was detcrrnined by t h e macro

K j e l d a h l d i g e s t i o n procedure (Brernner, 196.5). The ammonia

(NII ) from t h e d i g e s t i o n w a s d i s t i l l e d w i t h 45% N a 0 H i n t o 2.5% 3 b o r i c a c i d and t i t r a t e d w i t h 0 . 0 5 N IiC1.

A v a i l a b l e Phosphorus

A v a i l a b l e phosphorus was de termined by Bray I1 s o i l

e x t r a c t a n t ( B r a y and K u r t z , 19451, u s i n e 0.03N ammonium

f l o u r i d e w i t h 0.1H HC1. The phosphorus in t h e e x t r a c t was

determined w i t h a p h o t o - e l e c t r i c c o l o r i r n e t e r .

C a t ion Ihchanlye - Capaci ty , To t.11 Exchanf;enblc A c i d i t y ,

Exchi.n~;.eahl e Sodium, Po t ancium , Cal cj u1.1 crncl Mu(:nesiua

C a t i o n exchange Capuc i ty [CEC) w a s detcrrnined by t h e

a.rm,oniurn acet : i t t . di~placcmcnt rnethad and t i t r a t e d with s t a n d a r d

0. IT1 ITaOII ( J a c k s o n , 1958). T o t a l exctinn~:.eable a c i d i t y w a s

d c t c r d n c d by t h e t i t r i r n c t r i c method o f KeLeun C1982) ;

exchangeab le P k and K were measured by l%me photometry ;

c x c h a r r ~ c a b l e Ca and Fig were determined using the EDT6 - [Xthyleme diamino-tetra-acetic-acid) complexomctr ic t i t r a t i o n

Sodium AJr.or_pti o n R.1 l . io (SARI a n d l lxc11nnf .p:~bl . Sodium ---- - -

Sodiuci s d s o r p t i o n r a t i o ( s A I ? ) was c a l c u l . a t e d u s i n g the

and cxchanl:.e;lble sodium p e r c e n t a g e (ESP) c a l c u l a t e d as

+ ESP = Exchaneeable Na 100 - x - - -

1 - ( 6 )

a b s o r p t i o n s p c c t r o photometry ( p e r k i n Elmer Model 560,

Pcrkin Elmer Gorp. C'l') a f t e r t h e samples were diges ted in

c o n c c n trated I iNO 3

- IICLG4 ( 2 : l ) .

Carton Dioxide Evolution

?'he evolved carbon dioxide from t h e incubated s o i l

smiples was trapped in IN NaOH and calculated by back

t i t r a t i o n w i t h standard I N HC1 to a pheno lphtha le in @d point

after p r e c i p i t a t i n g t h e carbonates with 3 al, IN BaC12

s o l u t i o n . ( B l o m and Edelhuusen, 1955). The s o i l samples

were incubated and t i t r a t e d f o r t h e C02 at 7 days i n t e r v a l s ,

f o r a p e r i o d of 12 weeks.

C o l i f o r r n c a n d F e c a l C o l i f o r m Micro-Organisms

Yhc p r c s e n c c o f c o l i f o r r n s and f ' . \cnl c o l i f o r r n n m i c r o -

o r g c i n i s ~ n s i n the w s s t e - w a t e r w a s detcrrrlincd. by t h c s e r i a l

d i l u t i o n method u s i n c 0.85~ s t e r i l e s a l i n e , itIac Cankey Agar

C r y s t a l V i o l e t a n d n u t r i c n t Agar P l ~ t c s m e d i a , i n c u b a t e d a t

0 35 C f o r 12-24 h o u r s d11d. t h e c o l o n y f o r m i n g u n i t (cFU)

ob t ; ' i nc -d as d t ! s c r i b e d by Sh i pc a n d Ctlrucrorl (1954).

h t s B n s l y s i s

I n o r d e r t o a s c c r t u i n w h e t h e r t h e r e w e r c differences i n

s o i l c h a r a c t e r i s t i c s i n t h e a r e a s u n d e r i n v e s t i g a t i o n ,

T - t e s t ~ t n t i s t i c n l p r o c e d u r e w a s c a r r i e d o u t t o compare t h e

mean v a l u e s o f t h e s o i l p r o p e r t i e s and c r o p p e r f o r m a n c e s

b e t w e e n t h e s o i l s o f t h e sewage and non-sewage disposal

a . Thc r e l a t i o n s h i p s amongst oil p r o p u r t i c c were

p e r f o r m e d using c o r r e l a t i o n analysis. All s t a t i s t i c a l

a n a l y s i s were performed u s i n g t h e methods of S t e e l and T o r r i e

(1980).

CHAPTER FOUR

4.0 lU5UL'I'S kN1) DISCUSSION

4.1 S o i l M o r p h o l o ~ y

The s o i l s of t h e s t u d y a r e a a r e r e p r e s e n t e d by p r o f i l e s

S/NSK/l and S/NSK/Z f o r t h e sewage d i s p o s a l a r e a and NS/NSK

f o r t h e non-sewage d i s p o s a l area. The s o i l s a r e d e r i v e d from

wea the red Fnlse-Bedded S a n d s t o n e s , deep , and somewhat

e x c e s s i v e l y d r a i n e d . Colour of t h e s o i l s v a r i e d from dark

. . r e d d i s h brown (2.5 YH 3/61 t o Bed ( 1 0 H 4/6) i n NS/N-% p r o f i l e

a n d Very d a r k r e d d i s h brown (2.5 YR 2/21 t o r e d d i s h brown

( 2 . 5 YH 4/61 i n s / N s K / ~ and S / N S K / ~ p r o f i l e s .

The v a r i a t i o n s i n t h e Fluncell c o l o u r i n t h e sewage and

non-sewage s o i l p r o f i l e s c o u l d have been due t o t h e c o n t r i b u t ' i o n s .

of t h e sewage s l u d g e and e f f l u e n t s t o t h e s o i l colour.

This agrees w i t h t h e o b s e r v a t i o n s of T i a r k s e t al. (1974)

t h a t o r g a n i c m a t t e r i m p a r t s a grey, d a r k grey o r dark brown

c o l o u r t o s o i l u n l e s s o t h e r constituents, s u c h as i r o n o x i d e

o r un accumulu t ion of salts, modi f i ed the c o l o u r .

4. 2 S o i l Phy:>i c s l P r o p r . r t i c s

4.2.1 T e x t u r e

The p a r t i c l e s i z e a n a l y s i s ( T a b l e 4 ) shows t h a t t h e

t e x t u r a l c l a s s e s were mainly s a n d t o loamy s a n d o n t h e t o p

s o i l and sandy loam i n t h e subsoil. The dominance of c o a r s e

t e x t u r e i n a l l t h e profiles i s a t t r i b u t a b l e t o t h e False

Bedded S a n d s t o n e g e o l o g i c a l f a r m a t i o n s of t h e a r e a where t h e

s o i l s o c c u r ( ~ ~ t a m i ~ b o and Asadu, 1983).

Clay c o a t e n t was g e n e r a l l y low. The v a l u e s ranged from 6% .

t o 18% i n a l l t h e profiles, i n c r e a s i n g w i t h dcp th i n t h o

oewuce u o i l p r o f i l e c , but ~ h o w c d no dofinito trond in tho non-

sewage s o i l p r o f i l e s .

Silt contunt was very low i n a l l t h e p r o f i l e s . 'lhe

values ranged from 2$ t o 10% w i t h a mean of 5%, and showed

no d e f i n i t e t rend wi th dep th i n a l l t h e p r o f i l e a . The h i g h e s t

value of 10% silt c o n t e n t was r ecorded f o r t h e Ap and E

h o r i z o n s of t h e non-sewage s o i l p r o f i l e . The low c l a y and

silt c o n t e n t s observed i n t h e Ap hor izon i n this s o i l are

i n d i c a t i o n s of t h e degree of weather ing and l e a c h i n g which t h e

s o i l has undergone, f u r t h e r conf i rming the o b s e r v a t i o n of

-Obi and Asiegbu (1980) t h a t t h e low c l a y and si l t c o n t e n t s

o f s u r f a c e a011 h o r i z o n s i n t h i s a r e a were a t t r i b u t a b l e t o

high d e t a c h a b i l i t y and t r n n s p o ~ t a b i l i t y o f these l i g h t e r

m a t e r i a l s .

Sand c o n t e n t was g e n e r a l l y high i n t h e Ap h o r i z o n s w i t h

a mean of 802: and 857; i n non-sewage and sewage s o i l p r o f i l e s ,

sespoctivdly. T1ha nswnec aoil profile showed t h e h i g h e s t

s a d con ten t of 90% probably due t o h i g h d i s p e r s a b i l i t y

observed i n t h e sewage soil which may have caused t h e clay and

silt f r a c t i o n s t o b e d i s p e r s e d and washed away. Thus, t h e

high m n d c o n t e n t i n t h i s p r o f i l e was no t s u r p r i s i n g . C u r t i n

e t nl, (13p1t.) r ecorded t h e importuncc. of d i o p c r a i b l e c l a y as

a measure of s o i l s t r u c t u r a l i n t e r g r i t y and t h e i m p l i c a t i o n s

f o r w a t e r i n f i l t r a t i o n and r e t e n t i o n .

A t e s t of mean d i f f c r c n c e c u r r i e d out t o compare t h e

m a n v a l u e s o f t h e p a r t i c l e s i z e a n a l y s i s da t a between t h e

s o i l s o f t h e sewage and non-sewage d i s p o s a l a reas showed

t h a t t h o mean p c r c c n t s u n d c o n t e n t i n t h e scwagc s o i l was

c i ~ n i i ' i c u n t l y h i ( ;hcr t h ~ ~ n t h a t of t h ~ non-oewaly s a i l , whereas

s i l t and clay c o n t e n t s o f the two s o i l s were n o t s i g n i f i c a n t l y

d i f f e r e n t ( P 7 0.05) (Table 61.

4.2.2 Bulk Density a n d Pore S i z e D i s t r i b u t i o n

The b u l k d e n s i t y v a l u e s ranged from 0.71 t o 1.69 g cm -3

f o r t h e sewage s a i l and 1.45 t o 1.64 g f o r t h e non-sewage

n o i l (Table 4 ) . T h e low b u l k d e n s i t y va lues a f 0.71 and

0.83 g cmw3 ( b u t w i t h o u t c o r r e s p o n d i n g changes i n t o t a l

p o r o s i t y ) obse rved i n t h e AB h o r i z o n i n t h e sewage s o i l

p r o f i l o c were duc t o tho uccumulu t ion o r hurnifir-tl oowcrge

r n a t c r i a l s i n t h i s ho r i zon . The f u c t t h a t o r g a n i c matter

uuu:ilLy I ~ ~ r r i :L vrbry 1 aw b u l l < dt-n::.i 1.y 1:. 111 t~~:rocernrbnh w i Lh

similar low v a l u e s ( 0 . k a n d 0.8 g r e p o r t e d f o r N-Viro

soils by Logan and Har i son (1995).

Apart from t h e l o w bulk d e n s i t y v a l u e s o b s e r v e d i n t h e

AB h o r i z o n i n the sewage s o i l , bulk d e n s i t y v a l u e s were h i g h

i n a l l other h o r i z o n s . The i n c o n s i s t e n t p a t t e r n i n t h e

v a r i a t i o n of b u l k d e n s i t y w i t h dep th i n t h e fiewage s o i l

profiles i n c o n t r a s t w i t h the c o n s i s t e n t t r e n d i n the non-

sewage s o i l p r o f i l e s u g g e s t s t h e p r e s e n c e o f d i s c o n t i n u i t i e s

w i t h i n t h e Eewage s o i l p r o f i l e s due t o e x i s t e n c e of hunl if ied

sewage r n n t e r i : ; l layers i n t l i e : ;o i l .

that the d c r ~ r i t y of t h e p r i m a r y particle:; r i t t l i e r t h a n d i f f e r e n c c r

in structure was responsible for the observed b u l k d e n s i t y

v a l u e s . Furthermore, t h e high bulk density o b t a i n e d i n t h e

s o i l 6 i s r e f l e c t e d i n the low t o t a l and m a c r o p o r o s i t y o f t h e

soils. The non significant d i f f e r e n c e ( P . 7 0.05) i n mean

bulk d e n s i t y a n d total p o r o s i t y v a l u e r in t h e two s o i l s shcwed

t h a t l a rge a p p l i c a t i o n s of sewaEe s l u d g e a n d effluents o v e r

a l o n g p e r i o d of t i m e d i d n o t r e s u l t i n p o s i t i v e improvement

f u r t h e r c o n f i r m s t h e o b s e r v a t i o n made by O l s e n e t a l . (19')0)

t h a t s h o r t - t e r m low a p p l i c a t i o n o f sewnL;c c f L l u o n t t o r i o i l

y i e l d e d p o s i t i v e improvement i n t h e s o i l b u l k d e n s i t y and

p o r o s i t y , b u t l a r g e a p p l i c a t i o n s o v e r a l o n g p e r i o d o f t i m e

d i d n o t r e c u l t i n p o s i t i v e improvement o v e r t h e c o n t r o l .

P o ~ - e s i z e d i s t r i b u t i o n v a r i e d t o a g r e a t e r e x t e n t i n

sewage s o i l s compared w i t h t h a t o f t h e non-sewage s o i l . The a

h i ~ h m i c r o - t o i n a c r o - p o r o s i t y r a t i o o b s e r v e d i n t h e sewage

s o i l ( T a b l e 4) c o u l d make f o r C 0 2 b u i l d - u p a n d t o x i c i t y t o

b o t h p l s n t r o o t s and micro-org; in isms. T h i s , f u r t h e r

s u p p o r t s a s s e r t i o n made by Pngliui a n d U e N o b i l i (1993) t h u t

adequate proportiun of micro- t o m a c r o - p o r o s i t y w a s

1lccc:;:;ury for tllc cxi:;tcnce of continuou:; air d i f f ' u ~ i o n .

pathways in t h e s o i l .

Sewage

4.2.2 Water R e t e n t i o n C h a r a c t e r i t j t i c s

V o l u m e t r i c w a t e r c o n t e n t a t s a t u r a t i o n r anged from 0.39

t o 0.49 f o r t h e sewage s o i l a n d 0.40 t o 0.53 f o r t h e non-sewage .

s o i l ( T a b l e 5) . The 60 cm t e n s i o n s w a t e r c o n t e n t ,

r e p r e s e n t i n g f i e l d c a p a c i t y , w a s 5% l e s s t h a n t h e s a t u r a t e d

w a t e r c o n t e n t f o r sewage and 119: l e s s f o r non-sewage s o i l s .

The h i g h m o i s t u r e r e t e n t i o n a t 60 cm t e n s i o n o b s e r v e d i n t h e

ALJ h o r i z o n f o r t h e sewage s o i l can 'be a s c r i b e d t o t h e w a t e r

a d s o r p t i o n c a p a c i t y o f o r g a n i c m a t t e r ( ~ e t z g e r and Yaron, 1987).

F i g u r e s 1 and 2 show t h e s o i l m o i s t u r e c h a r a c t e r i ' s t i c c u r v e s

d c t c r m i n ~ t i on u n d i s t u r b e d s o i l corer ; f rom d i f f e r e n t h o r i z o n s .

'yhc s teepnes : : o f t h e c u r v e s shows t h a t m o i s t u r e r e l e a s e

i n c r e a s e d s h a r p l y between 0 cm a n d 60 cm w a t e r t e n s i o n s i n

t h e kp h o r i z o n i n a l l t h e p r o f i l e s , i n d i c a t i n ~ t h a t a h i g h

p e r c e n t a g e of t h e s o i l w a t e r h e l d by t h e s e t o p s o i l s w a s

i n t h e mac ro -pores , m o s t l y a t t r i b u t e d t o t h e h i g h s a n d c o n t e n t

i n t h e Ap h o r i z o n of t h e s e s o i l s .

Water c o n t e n t a t 3 0 cm, 60 cm, a n d 100 cm t e n s i o n s w a s

h i g h e s t i n t h e All h o r i z o n o f t h e sewage s o i l p r o f i l e s ( F i g . I )

due t o t h e h i g h a c c u m u l a t i o n o f h u m i f i e d sewage m a t e r i a l s i n

this h o r i z o n . The r e s u l t f u r t h e r shows t h a t a b o u t 50% o r

more o f t h e t o t a l w a t e r h o l d i n g c a p a c i t y and more t h a n 70%

o f t h e w a t e r h e l d a t 60 cm t e n s i o n w a s r e t a i n e d a t 100 crn

w a t e r t e n s i o n i n t h e Ab h o r i z o n o f t h e sewage d i s p o s a l s o i l .

T h i s compared w i t h a b o u t 407; o f t h e t o t a l w a t e r h o l d i n g

-- -- --- 3--- -- -. Dopl1l V01ume t1 . i~ I;!() i:, t u r e 1Iydruul ic : Dispel& Purmea-

3 ewng c AB 15-35 0.47 0.40 4.21 98 Jbderate S o i l

LB 35-55 0.40 0.23 7.89 98 Moderate- ly rapid

13 tl 55-105 0.42 0.28 73-15 9'1 Rapid

; ; u j ~ ~ ~ l , l ~ , j nlr ,I L.4 5 0, IIO 0.I10 11 . 71 38 Pk, ( I C I t - i 4 t 0

s o i l Elj 43-65 0.112 2.3 7-39 98 Moderate-

ly rapid

Ut I "5-80 0.46 0.36 13.15 88 R a p i d

13t 80-150 0.39 0.27 19 .It7 80 li i ipid

Mean 0.lf-7 0.3 2 13.05 92 Rapid

r;s/~s# AP 0-1 It 0.51 0.25 2h. 7 2 6 Very r ap i d

Florl- liU 111-37 0.53 0.25 17.10 75 R a p i d 2 ewa ge SOL^ E 37-76 0.45 0.30 16.78 42 Rapid

B t l 76-90 0.40 0.32 19-39 67 R a p i d

B t 90-160 0.44 0.33 19.4-7 80 R a p i d

Mean 0.47 0.30 20.52 65 Rapid

I ( a ) NSINSK

C a, -, 020- U

Tension (Cm)

Fig.1: Soil moisture characteristic curves of the soils at different depths.

N S I N S K A S I N S K I 1

SINSKI2

Tension ( Cm )

Fig.2: Mean moisture characteristic curves of the soils.

!. c ' J

c a p a c i t y and 50$ o f t h e w u t e r h c l d u t 60 ctn t c n a i o n r e t a i n e d

at 100 cm w a t e r t e n s i o n i n t h e AB h o r i s o n o f t h e non-sewage

s o i l (Fig. I). T h i s r e s u l t shows t h a t a c t u a l l y t h e amount

of w a t e r r e t a i n e d a t t h e s e t e n s i o n s i n t h e AB h o r i z o n o f t h e

s e w a g e s o i l w a s c o n t r i b u t e d by t h e amount o f o r g a n i c m a t e r i a l s

a n d t h e dominance o f m i c r o - p o r c s i n t h i s h o r i z o n . It w a s

n o t klowcver s u r p r i s i n g t h a t t h e a v e r u g e s o i l m o i s t u r e r e t e n t i o n -

a t 0 cm, 30 crn, 60 cm, and 100 cm t e n s i o n s was i n t h e o r d e r

o f / I K 7 S/NSK/I 7 S/NSK/2.

Thir , t r e n d c o u l d b e a t t r i b u t e d t o t h e non-homogenuous

c o n t i n u i t y i n t h e sewaEc s o i l p r o f i l e c . A l s o t h e p o s s i b l e

d c v e l o p m c n t o f w a t e r - r e p e l l e n t waxy s u b s t a n c e s which r e d u c e d

m o i s t u r e r e t e n t i o n c a p a c i t y as a c o n s e q u e n c e o f l o n g t e r m

d i s p o s a l o f s e w a g e s l u d g e a n d e f f l u e n t s c a n c o n t r i b u t e t o

t h i s and i s i n a g r e e m e n t w i t h t h e s t u d y o f F i a r k s e t a l e (1974).

However , t e s t o f mean c o m p a r i s o n showed t h a t t h e mean s o i l

m o i s t u r e . r e t e n t i o n a t 60 cm t e n s i o n ( f i e l d c a p a c i t y ) d i d n o t

d i f f e r s i g n i f i c a n t l y ( P ~ c 0.05) i n t h e two s o i l s ( 'Tab le 6 ) .

4.3.4 S a t u r a t e d I I y d r a u l i c C o n d u c t i . v i t y a n d D i s p e r s i o n R a t i o '

S a t u r a t e d h y d r a u l i c c o n d u c t i v i t i e s were h i c h l y v a r i a b l e

i n t h e s e w a g e s o i l , b u t c o n s i s t e n t i n t h e non-sewage s o i l

( T a b l e 5 ) . P e r m e a b i l i t y c l a s s r a n g e d f r o m m o d e r a t e t o r a p i d

f o r sewage s o i l s a n d r a p i d t o v e r y r a p i d f o r t h e non-sewage

s o i l .

T a b l e 6 : Some s o i l c h a r a c t e r i s t i c s i n t h e sewage and non sewage d i s p o s a l a r e a s

C a l c u l a t e d p rope r t i c s C a l c u l a t e d P r o p e r t i e s t - v ~ l u e s t - v a l u e s .-... - . .

1 .I 49ns Exchangeable C a 2.437" (Crnol kg-I

H y d r a u l i c c o n d u c t i v i t y ( c m h r l ) 3 21 2* & c h a n g e a b l e Mg 1 .46ons (Cmol kg-q

Water r e t e n t i o n at 6 0 cm t e n s i o n (cm3 cm-3)

Exchangeable kl 0.851 nS 0.9~7"' (Cmol kg-l )

E l e c t r i c a l c o n d u c t i v i t y (mmhos cm-I)

S a l t c o n c e n t r a t i o n (mg 1-I )

p H (H20)

T o t a l o r g a n i c m a t t e r (2;)

2,489"' CO E v o l u t i o n (PIg 1 0Clg-I )

2.948'

T o t a l N i t r o g e n (%) 2.888' .-- - .. .- - -- -

ESP - Lxchangeuble sodium p e r c e n t a g e

SAH - Sodium a d s o r p t i o n r n t i o

- Mean w e i ~ h t d i a m e t e r o f w a t e r s t a b l e a g g r e g a t e s

*' - S i g n i f i c a n t at P < 0.01

* - S i g n i f i c a n t a t P ( 0.05

n s - N o n s i g n i f i c a n t

S u t u r u t c d h y d r a u l i c contltic t i v l . t y vtlluo ur; low u s

lt.21 crn h r - I , was o b t a i n e d f o r t h e AB' h o r l z o n in the aewage

-1 s o i l p r o f i l e s compared t o 17.10 crn h r for s imi la r h o r i z o n

i n t h e non-sewage s o i l p r o f i l e . The r e d u c e d p a r m e a b i l i t y

observed i n t h e sewage s a i l i s e v i d e n c e t h a t l ang - t e rm

a p p l i c a t i o n of sew2ge sludge a n d e f f l u e n t s c o u l d lower s o i l

hyc l rnu l i c coliduc t i v i t y , p r o b : h l y due t o I;hv f r lr-rn;~ t.i o n of a

b i o l o ~ i c n l mat o r crust, I t may a l s o be due t o t h e a c c u f l u l n t i o n

of s o l i d s f i l t e r e d from t h e e f f l u e n t a n d / o r t h e c o l l a p a e of

s o i l s t r u c t u r e due t o o r g a n i c m a t t e r d i s s o l u t i o n . K r i s t i a n s e n

( 1 9 8 1 ) ~ and Liefferine and McLay (1996) made similar

o b s c r v n t i o n s t h a t l ong - t e rm a p p l i c a t i o n s o f o r g a n i c w a s t e

cuch na sewage sludge and e f f l u e n t s s i g n i f i c a n t l y r e d u c e d s o i l

p a r m e a b i l i t y and that t h e r e d u c t i o n s i n p e r m e a b i l i t y were

a t t r i b u t a b l e t o t h e accui r~ul i l t ion o f s o l i d s f i l t e r e d from t h e

e f f l u e n t s and the c o l l a p s e o f s o i l s t r u c t u r e due t o o r g a n i c

matter d i s s o l u t i o n .

D i s p e r s i o n r a t i o , as n measure of s o i l s t r u c t u r a l

i n t c r ~ r i t y , lint, been u:,cd t o i d c ~ ~ t i r y coils t h a t are p a r t i c u l a r l y

s u s c e p t i b l e t o s l a k i n g , c r u s t i n g , r e d u c e d i n f i l t r a t i o n and

increased e r o s i o n d u r i n g r a i n f a l l . Table 5 shows t h a t t h e

di:;pr:r:,ion ratios arc vury hly;h, rungirlg from 80% t o 98% i n

t h e sewage sail p r o f i l e a , a n d 42): t o 80% i n t h o non-sewage .

profile, w i t h t h e h i g h e s t value of 98% o b s e r v e d i n t h e

AB horizon of t h e sewage s o i l . The t r e n d is similar t o t h a t

of h y d r a u l i c c o n d u c t i v i t y measurements.

The h i g h d i s p e r s i o n r a t i o s obse rved i n t h e Gcwago s o i l

c o u l d cause agcregate breakdown a n d s u b s e q u e n t clay d i s p e r s i o n

lending t o p o r e b lockage and surface c r u s t i n g which a c c o r d i n g

t o C u r t i n ct ~ 1 . (1994) h a v e i m p l i c a t i o n s f o r low w a t e r

i n f i l t r a t f o n ant1 r r : tr:r~Lion and hick1 ? ; o i l c ~ ~ ~ i o n .

f~ .?.5 l ~ g g r l : ~ ; ~ I,(: S ~ : I \ I i I 1.y

Aggregate s t a b i l i t y , us measured by s i n v i n e a w e t t e d

sample t h r o u g h a n e s t of s i e v e s of v a r y i n g cizefi, i s a measure

of t h e s t r u c t u r a l s t a b i l i t y of s o i l a g g r e g a t e s a g a i n s t t h e

s l a k i n g e f f e c t a n d k i n e L i c energy d i s r u p t i o n of moving wa te r .

Thc d i s t r i b u t i o n of t h e w a t e r - s t a b l e aggregates i s shown i n

' l ab lo 7. 'Yhe mean weigh t d i a m e t e r (w~D) v a r i e d from 0.44 t o

1.68 mm. Generally, t h e t a p s o i l MWD v a r i e d i n t h e o r d e r of .

S/NSK/Z 2 SS/NSK/l ;7 NS/N%, where as t h e o v e r a l l means

v a r i e d i n t h e o r d e r of NS/NSK 7 s /NsK, /~ 7 SJNSKJI.

'L'llc low uKgregnta s t a b i l i t y i n t h e sewage s o i l , p a r t i c u l a r l y

i n t h e macro -aggrega te f r a c t i o n s t e n d s t o c o n f i r m t h e possibility .

of macra-a6gregnte breakdown as a renul t of ion[:-term dlfipooal.

of sewage sludge and effluents on t h e s o i l . The non-sewage

soil pllof i l c h a s r e l a t i v e l y more s t a b l e a g g r e g a t e s ,

p a r t i c u l a r l y i n t h e mac ro -aggreea t e f r a c t i o n s ( T a b l e 71,

thuc, c o n f i r m i n g t h e o b s e r v a t i o n of Igwe (19941 t h a t u l t i s s l s

are g e n e r a l l y w e l l aggregated as a result of age and pro longed

ox ida t i on - reduction processes. Conver se ly , the l o w MWD

of w a t e r table aggregates i n t h e RU h o r i z o n i n t h o sewage

T a b l e 7: h ~ g r o ( ; a t e stability of t h e so i l . , 36 year:; n f tcr sewage sludgc and e f f l u e n t s d i s p o s q l

- A ~ c r c ~ a t e S i z e s (mm) -- ram Profile JIor-jzon D e p t h 4.75-2 2-1 -1-0.5 0.5-0.25 0.25 (nun)

Suwn~;c ! All 15-35 9.6 19.1 21.0 29.9 20.4 0.92 S o i l

It; 13 35-55 70-7 9 20.9 26.6 20.9 0.98

~ e a n 9 9 16.6 21.0 26.7 25.8 0.94 .... - ---

S e w a ~ c AU 18-43 10.0 19.2 26.5 31.0 13.3 ' 0.96 Soil

I233 43-65, 10.0 20.2 32.7 13.8 3 .3 '1.00

Mean 11.9 I 23.8 23.5 19,4 1.08 .~- - - - - -.--.

Nan oewall;c U 3/1-37 23.0 111.2 23.7 23.0 16.7 1.-33 Soil

L 37-76 30.8 17.3 20.8 18.9 12.2 1.56

J i ~ p o s d s o i l p r o l ' i l c s a c m e s wiLh Mbuf:wu (79891, and

Eps tc fn (73751, t h a t o r g a n i c wattex. C;rtl a c t a5 c l i . 6 n p ; g r c ~ : ~ t i n ~

agent i n t h e s o i l because t h e d i s s o l v e d salts, p a r t i c u l a r l y

Na, a p p l i e d t o t h e s o i l v i a o r g a n i c wastes can r e p l a c e Ca,

disperse s o i l aggref;:ite:;, dc:;troy .soil s t r u c t ~ r c . , rind r e d u c e

w a t e r p e r m e n b i l i t y . 4.3 Sodium A d s o r p t i o n R a t i o , Exchan~cable Sodium P c r c e n t a a e ,

E l e c t r i c a l ConductLvi ty , S a l t Concen t r a t ionA T o t a l C u t i o n

C o n c e n t r a t i o n and Osmotic P r e s s u r e

Measurcrncnts of sod ium a d s o r p t i o n r a t i o ( S A R I , and

cxcllaril:.ectble sodium purccnta[r;e (ESP) a r e based p r i m a r i l y on

c o n d u c t i v i t y of t h e s a t u r a t e d s o i l e x t r a c t (lice) can b e used

d i r e c t l y f o r a p p r a i s i n e t h e effect of s o i l salinity on p l a n t

growth. F u r t h e r m o r e , s a l t c o n c e n t r a t i o n , total c a t i o n

c o n c e n t r a t i o n , and osmot i c p r e s s u r e have b e e n u s e d as an i n d e x

of t h e wiltinp; c o - e f f i c i e n t of s o i l s and honce t h e q u a n t i t y

of w a t e r t h a t a s o i l will s u p p l y t o plants.

l 'able 8 shows t h e values of sodiuln adaorptian r a t i o ,

cxchangcnble sod ium pcrcentbge, e l e c t r i c a l c o n d u c t i v i t y ,

pressure of t h e s o i l s .

v i t h t h e h i g h e s t v a l u e o f 0.13 r e c o r d e d f o r the sewage s o i l

p r o f i l e , i n d i c a t i n g t h a t a h i g h p e r c e n t a g e of o x c h u n g c a b l e

sodium has been b u i l t up i n t h i s s o i l , If the non-sewage

d i s p o s d s o i l i s c n s i d e r e d t o be n baseline f o r compar ison ,

i t i s e v i d e n t t h a t l ong- t e rm a p p l i c a t i o n of t h e s l u d ~ e and

e f f l u e n t s s i g n i f i c a n t l y i n c r e a s e d t h e e x c h a n ~ e a b l c sodium

c o n c e n t r a t i o n i n t h e t o p s o i l and s u b s o i l of t h e sewage s o i l s

by 39;: and 19$, r ~ : ; p e c t i v c l y (Tub lc 8) . ilicl1 S ~ l i cnn causc an

i l r c r u ~ r ~ ~ o i 1 1 1111- L ( ~ I I ~ I : ~ I C : ~ 01' I. h t , 1m1.L 1.0 11 L : I ~ U ~ I L I Y .

L l c c t r i c a l conduc L i v i t y , t iul L C O I ~ C L ' ~ ~ 1ruLiotl atid aurn0L.L~

p r e s s u r e v a l u e s of t h e s o i l s gave s i m i l a r p u t t e r n as that of

the Sad< and dSP, b e i n g much h i g h e r i n t h e sewage s o i l .

The i rnp1ic ; i t ions ai' this development a r c t h a t yields of

sal t s e n s i t i v e c r o p s may be r e s t r i c t e d a c c o r d i n g t o B e r n s t c i n .

(1964) c l a s s i f i c a t i o n of s o i l s a l i n i t y . Fu r the rmore , t h e salts

may i n t e r f e r e with t h e a b s o r p t i o n of w a t e r by p l a n t s through

r e d u c t i o n i n t h e s o i l o smot i c water p o t e n t i a l and t h u s

d e c r e a s i n g t h e amount of w a t e r t h a t would be r e a d i l y a v a i l a b l e

f o r p l a n t uptake and i n c r e a s i n g i n t h e w i l t i n g c o - e f f i c i e n t

o f s o i l s . Thic; a s s e r t i o n a g r e e s with t h e o b s e r v a t i o n s of

blagesan et a l . 11996) and Ham and Uowdy (1975) t h a t h i ~ h sal t

c o n c e n t r a t i o n s i n t h e s o i l deve loped v i a hcuvy application of

m u n i c i p a l e f f l u e n t s i n t e r f e r r e d with t h e a b s o r p t i o n of w a t e r

by soyabecin t h r o u ~ h r e d u c t i o n i n t h e c o i l o s m o t i c w a t e r

p o t e n t i a l .

.. .- .

-.---- -

6- I--

age BB

. n - 1

in ( 19

4.4 S o i l Chemical P r o p e r t i e s

T a b l e 9 shows t h e pH, t o t a l o r g a n i c mat te r , a n d t o t a l

n i t r o g e n d i s t r i b u t i o n s in t h e s o i l . The s o i l pi1 was

g e n e r a l l y ex t r eme ly a c i d f o r t h e sowage s o i l and r anged

from s t r o n g l y acid t o v e r y s t r o n g l y a c i d f o r t h e non-sewage

soil. In a l l cases, t h e pH tended t o d e c r e a ~ e w i t h dep th .

The e x t r e m e l y ac id nature of t h e sewace s o i l c o u l d be

a t t r i b u t e d t o t h e d i s s o c i a t i o n o f weakly a t t a c h e d hydrogen

i o n of t h e p h e n o l i c and amino g roups p r e s e n t i n s o i l o r g a n i c

m a t t e r und t h e i n h c r c n t a c i d i c n a t u r e of t h e h i g h l y wea the red

c o i l s ol' t i le South-ear;tt!rn N i l ~ o r i i l u s e a r l i c - r ob:jerved by

Alcan i~bo and lgwe (1990b). However, t e s t o f mean compar ison

showed a non s i g n i f i c a n t ( P > 0.05) d i f f e r e n c e i n t h e mean

pH v a l u e s f o r t h e sewage and non-sewage soils ( T a b l e 6 ) .

Organic m a t t e r c o n t e n t of t h e s o i l s was v e r y low t o h i g h

i n t h e sewage s o i l and low t o modera te i n t h e non-sewage s o i l

( T a b l o 9). 'llhc s o i l orgnnj.c m a t t e r deceased with d e p t h i n

a definite p a t t e r n i n t h e non-sewage s o i l , but v a r i e d

c o n s i d e r a b l y i n t h a t o f sewage s o i l . The h i g h l e v e l of organic

m a t t e r o b t n i n e d i n t h e sewace s o i l i n c o n t r a s t t o t h a t o f

t h e non-stwa[;c s o i l i s one of t h e i m p o r t : ~ n t a t t r i b u t e s of

scwu@c sludc;c iind cff1upnt .s t h a t maker f o r i t s u t i l i z a t i o n

i n a g r i c u l t u r n 1 l a n d . T h i s a t t r i b u t e h a s rrx>de t h e a e ; r i c u l t u r c t l

land d i s p a c d and /o r u t i l i z ; ~ t ion of scwagc s l u d g e and

c f l l u c n t s as a v a l u a b l e a l t e r n a t i v e i n t h e management of s o i l

Table 9: The pH, anganic matter*, to ta l nitro!:cn oi Lila s o i l , 36 y c b r s a f t e r sewuec sludge and e f f l u e n t s d i s p o s a l .

H % % A v a i l a b l e P P r o f i l e l l o r i aon Depth

2 Obfb NC ( ~ ~ r n )

Sewage AU 15-35 3.8 3.4 8.58 0,421 78.4 S o i l

8 35-55 3.6 3.3 I . 0.061 16.4

Sewage AB 18-13 3.8 3.!c 5.50 0.210 14.8 Soil

Lfi 43-65 3 . 3.3 1.36 0.060 11.6

Mean 3.6 3.3 3.01 0.113 13.8 -- --.

Non- AI3 14-37 4.5 4.1 1 -72 0.086 11.6 S cwngc S o i l 37-7G 4.4 3 . 8 1.52 Om(P"7 10.8

b O r g a n i c matter

c T o t a l n i t r o g e n

W r g n n i c m a t t e r = o r g a n i c C x 1.724 (Van Bemmelen f a c t o r ) .

f e r t i l i t y d e p l e t i o n a n d has become a t t r a c t i v e , e s p e c i a l l y i n

low o r g c n i c s o i l s .

I f t h e non-sewage s o i l p r o f i l e i s c o n s i d e r e d t o be a

b a s e l i n e f o r c o ~ n p a r i s o n , i t i s e v i d e n t t h a t l ong- t e rm

a p p l i c a t i o n o f t h e s l u d g e and e f f l u e n t s has i n c r e a s e d t h e

o r g a n i c m a t t e r c o n t e n t i n t h e Ap horizon from 2.06% t o 2,89X

( T a b l e 9 ) . Organ ic m a t t e r c o n t c n t as much as 8.58% was

r c c o r d e d f o r kB h o r i z o n i n t h e sewage s o i l p r o f i l e (s/'NsK/I

compared w i t h 1.724; o b t z i n e d i n a similar h o r i z o n i n t h e non-

sewage s o i l . T h i s confirrns a number o f r e p o r t s , i n c l u d i n g

t h o s e of Stadelmnnn and F u r r e r (1985) t h a t t h e o r g a n i c m a t t e r

c o n t e n t of a sandy loam s o i l was i n c r e u ~ e d from 1.5% t o 2.6% I -1

a f t e r 7 yea r s of applying sewage s l u d g e at a r a t e of 5 tha yr

Augers and N'hayegamiye (1991 and Ross e t a l . (1982).

' f 0 t ~ l n i t r o g e n had u s i m i l a r t r e n d as t h a t of organic

c n % l t h a n in t h e non-sewnga s o i l . . T h e h i ~ h n i t r o g e n c o n t e n t

a f ; soc i a t cd w i t h sewage s l u d c e and e f f l u e n t s c o u l d have been

r e s p o n s i b l e f o r t h e hi(;h c r o p y k l d s r e c o r d e d i n t h e l ow

o r g a n i c m a t t e r s o i l s t r e a t e d w i t h sewage s l u d g e and e f f l u e n t .

Horrever, t h e h i r h n i t r o g e n c o n t c n t i n t h e sewac;e soil could

be 0 e t r i m e n t a l to c rop p r o d u c t i o n , p a r t i c u l a r l y for l egumineous

c r o p s i n view of i t s i n t e r f e r e n c e i n t h e p l a n t a b s o r p t i o n of

potassum. Pa lozzo and Jenkins (1979) o b s e r v e d a d e c l i n e i n .

p l a n t and s o i l c o n c e n t r a t i o n of K.over a 4-year pe r iod of - -

. . l a n d a p p l i c a t i o n of cewn[;o waste-wotcr at t h e s i t e of t r e a t m e n t ,

turd rclated i t Lo t h e K : N r a t i o 01 t h r : G e W L I & p ? wic:;tc-wutcr

applied b e c a u s e t h e sewage was te-water c ~ n t ~ i i n c l d more than

twice as much N as K.

A v a i l a b l e P d i s t r i b u t i o n i n t h e s o i l s r anged from 10.4

t o 18.4 ppm, w i t h t h e h i g h e s t value of 18.4 pprn r e c o r d e d f o r

t h e AU h o r i z o n i n t h e s e w a g e soil, p r o f i l e (s/NsI(/I). The

t r e n d i n t h e p r o f i l e s ( T a b l e 91, t e n d s t o s u g g e s t t h a t t h e r e

was l i t t l e o r no l e a c h i n g of P , p r o b a b l y d u e t o t h e f o r m a t i o n

of coniplex coiripounds w i t h Fe iis a r e s u l t of t h e low pH v a l u e s

of t l l c s o i l . 'Yestar (1430) r e p o r t e d p o s s i b i l i t y of P f i x a t i o n

c~t low : . o i l p11 1 ~ : v c ~ l r : .

I k c h n n / : c n b l c Bases, Ac id i ty - and U m e Y u t u r n t i o n

T u b l e 10 shaws Chat exchangeable N a r anged f rom 0.06 t o

++ 0.20 Crnol kg-', K+ from 0.05 t o 0.23, Ce f rom 0.8 t o 2.8

and M ~ + + from 0.6 t o 3 . 0 , The AB h o r i z o n o f t h e sewage

soil p r o f i l e s ( s / N s K / ~ ) can~istently showed t h e h i g h e s t

values f o r e x c h a n g e a b l e bases . T h e changes i n CLC were lower

t h i n expec ted . T h i ~ was most likely due t o the f a c t t h a t

the m e t a l c added t o t h e s o i l c:m be complcxcd, t h u s c a u s i n g

a d e c r c a a c in the n c g a t i v c s u r f a c e chargc of L l ~ o o r g a n i c

mut ter .

Test of mean comparison shows s i g n i f i c n n t (PC 0.05

i n c r e a s e i n t h e mean Mg c o n t e n t o f t h e sewage soil. O t h e r

+ exchsnneab le b a s e s (ca2+ and X ) a l s o i n c r e a s e d i n t h e aewage

10:. S

ome ex

es -of---the soil. .

sewzge sludge and

nt disposal

0 . ..o

. ..f, .-

- 'o . 78

. . ..2;

Mean- '

S/NsK/2

Sewage

. . . .-

.. . -.

- M.--.

-.-l 3

. ;9- -.

. - - .. .

. "' "'

NS/NSK

Non Sewage AB

d i s p o s a l s o i l , a lcnougn nor; s~gnilicantly d i f i ' e r c n t a t

(I) 2 0.05) fronl .e 6 ) .

~ [ i ~ . h acculnu 1 0 1 ~c,q-' s o i l ) was

obse rved i n t h e s o i l p r o f i l e

(S/NSK/I cornpar -1 i n similar h o r i z o n

in Lhc non-r;uwatl; 1 ) . The h i l ~ h

cxchangcab le 11' ~ i l w a ~ most l i k e l y

due t o t h e pheno ;he o r g a n i c matter

of t h e sewage s o ' these g r o u p s would

yield 11" to t ~ ~ c . B L , l r r r 1 4 L b I l b u l t o c r u u c r c b A 7 ~ O U I d lower t h e : ;oi l .

pH and p l a c e rcs s t a i n crops that

may bc c c n L i t i v e one of t h e

c r i t i c ; ~ l l o n g t - m m h = o r . - r g - l n - A d i - - - - r d of L;CWU~C. s l u d g e

ex t r eme ly high

values are d i q

and B e r n a l e t E

, ~ * . , & A I - Y U I U Y V * .&Y.*U ...I",,".

LS extrenlcly l o w pll and i n

pH where sludge and effluc

3osed of on t h e s o i l . Keel

11. ('I9921 made s imilar as:

? n t s w i t h high pH

Ley 2nd Quin ( 1979). '

i e r t i o n s when the

?nts t o a s i l t loam s o i l wc

; n l s -

: r e s t u d i e d .

' . c o i l s a r c show]

m e t a l s i n s o i l :

:mi.i nns nf n nr~rnher of he^

. t i o n s of heavy

, o r of s o i l

senap;e s o i l p r o f i l e s .

Using t h c r: Lon-sewego ooil p r o f i l e af

:-t crm d i ~ p o : ; u l of :iowtlf;c

111sed an i n c r e a s e in Zn. I

; the b a s e - l i n e f o r

on to t h e s o i l ca ---- -- --------- - - , ?b, Cd, and Cu

concentrations i n t h e U p h o r i z o n by 611, 230, 39, and 479

p o r c c n t r e s p e c l B h o r i z o n , by 748,

234, 72, and 6t d , a n d Cu, r e s p e c t i v e l y .

T e s t o f mean cc t r a t i o n of Zn and Cu

i n t h e sewage and non-sewage ('A'able b), shows t h a t Zn and Cu

c o n c e n t r a t i o n s were s i ~ n i f i c a n t l v (P < 0.05) h i g h e r i n t h e

o f Pb a n d Cd were highly H i g n i s i c a n t \ r c 0.01) i n the sewil&+'e

tioil.

The hig h c o n c e n t r a t i o n s of t h e s e ne t :

P r n n f a m i n a f i n n w i f h Zn - Ph- (

11s i n t h e sewage

s o i l , v i a t h e sludge and e f f l u e n t s r e c e i v e d by t h i s s o i l o v e r

a l o n g p e r i n i n a t i o n of s o i l s . i s one of t

t he b e n e f i c

- .od of t ime. Heavy m e t a l contar

;he c r i t i c a l long-term h a z a r d s i

: i a l e f f e c t s of sewage s l u d g e a1

1 d C m : + h t l C I Q I \ c h n ~ ,

t h a t t e n d s t o n e g a t e

1d e f f l u e n t s d i s p o s a l

t o a g r i c u l t u l L z A .LCIIIuD. U I I , - L I . L I , , 7,1, uI.vned e v i d e n c e of s u c h

c o n t a v i n n t i o n in a snndv soil t r e a t e d w i t h sewage s l u d g e at

intervals of o v e r Of t h e e i g h t m e t a l s

s t u d i e d by Smith ( ,,, , , , I-..., ..-I ...- st p r o b l e m a t i c o f

. - .-

a p e r i o d of 25 years.

' I 0 0 1 ) v + n ~ w a n t h o m n

t h o s e cons:

Build. d l and CU) t o c r i t i c a l

T a b l e 11: Heavy metal a i s t r l a u t l o n In the soil p r o f i l e s , 36 yearo u f ter sewage sludge and e f f l u c n t ~ dicposal.

P r o f i l e i [ Iorizon Depth (cm) I'e Zn P1: I" F'n

Sewage AB Soil

0- 15 129 112.0 0.98

15-35 175 185.8 1.63

35-55 187 112.9 1.51

55-1 05 185 4.5 0.85

I 05-160 95 3.7 0.72

Mean 154 83.8 1.14

oa31 42

0.38 48

0.26 29

o. rs 11

BDL BDL

0.28 33

Sewage AB S o i l

0-1 8 156 114.1 0.87

1 8-43 198 129.7 1.64

43-65 205 106.1 1.48

65-80 186 12.1 0.92

80-7 50 125 11.7 0.90

Mean 174 74,8 1.16

Iion- AB Sewage S o i l E

0-14 218 I 0.28

14-37 157 18.6 0.49

37-76 239 21.3 0.24

76-90 165 5.7 0.18

90-160 291 4.9 BDL

Mean 194 1 3 0.30

0.16 4

0.08 2

BDL BDL

. - - ~

IL - U e l o w D e t e c t i o n L i m i t .

o t h e r hand , s: and t h e i r a c t i v i t i e s

a r e c r u c i a l t o m e ma in tenance or s o u f e r t i l i t y , t h e r e i s

s could have

~ n d c r o p p r o d u c t i o n .

.at e l e v a t e d heavy .

a p p l i c a t i o n s caused reduct ion I n s o i l m i c r o b i a l b iomass l e v e l s ,

i n h i b i t e d N2 . i v i n g and s y m b i o t i c

o rgan i sms , and reduced c e r t a i n enzyme a c t i v i t i e s s u c h as

u r e a s e and phospha ta se .

ctween o r g a n i c mc

al. s o i l (r = 0.01

and n o n - s i g n i f i c a n t c o r r c l n t i o u ( P > 0.05) w i t h .Ln :11111. Cd

t h e non-sewage s o i l . C a t i o n exchange capacity (CSC) a l s o

showcd a h i g h l y , p o s i t i v e c o r r e l a t i o n (P 4 0.01) w i t h Zn and

( P C 0.05) correlation w i t h Cu (r = 0.761) i n t h e sewage s o i l

b o t h

o ! r e l a t e d

t ~firrns

t .. (1982).

I I p r e d i c t o r s of heavy m e t a l c o n t e n t i n s o i l . l h l s ic poss i t l ly

n i c r f ~ t ~ l tcr .

duo t o t h e h i ~ h acitiorption oapacify of orgal

Ilence, as s o i l o r g a n i c m a t t e r i n c r e a s e s w i t ;

i n c r e a s e i n CEC, t h e r e i s t h e t endency f o r I

and Pb t o b e adso rbed o n t h e s o i l complex,

a v a i l a b i l i t y and a b i l i t y t o be p h y t o t o x i c i.

4.5 R e l a t i o n s h i p s among the s o i l p h y s i c a l *

Thc r e l a t i o n s h i p s among some ~ h y s i c a l :

h c o r r e s p o n d i n g

n o r c Zn, Cd, Cu

t h u s r e d u c i n g t h e i r

n t h e s o i l .

p r o p e r t i e s

p r o p e r t i e s o f t h e

sewage and non-sewage soils are snown I n ,xable 13.

C a I? 4 0.05) negative

cc t e n t and % s a n d .

m t y (r = -0,661) i n

t h P 1 0.05) n e g a t i v e

c c t e n t and $ s a n d , .

Ul iu u r , i k - a l . c , r l r ~ L C , L I L L ~ ~ J C , A I , ~ V t: G ~ ~ I . ~ = . L U ~ L U I L U C ~ W C C ~ % c l a y c o n t c n t

and t o t a l p o r o s i t y i n t h e non-sewage s o i l . C a l c u l a t i o n s a l s o .

show p o s i t i v e c o r r e l a t i o n s

(r = h y d r a u l i c c o n d u c t i v i t y

and Dn sewage s o i l s ,

respecLlvely. borrelsslons oecween s d ~ u r a t e d h y d r a u l i c

c o n d u c t i v i t tio on showed s i g n i f i c a n t

(P .( 0.01 ) p o s l t i v e correlation (r = 0,979) between s a t u r a t e d

h y d r a u l i c c o n d u c t i v i t v and m a c r o - ~ o r o s i t y , a n d n e g a t i v e

t e d h y d r a u l i c ~ a a d i s

a n o n - s i g n i z i c a n t ( P > 0.05) low, 1

0.176 and 0.225) between s a t u r a t e d

t o t a l p o r o s i t y i n b o t h sewage and'nc

_ I _ . - _ .I n - -, L 2 - - - L - L -.A.

y and p o r e s i z e d i s t r i b ~

scw:qy soils.

a i l n u a r rc lu t l o n s h l p s , u l thou1:h n o t r ; i (y i l ' i c : l n t , a l s o e x i ~ tod

for t h e noti :;cwo(:.o mils.

'lhc ncgu Live c o r ~ * e l n t i o n be tween % c l a y cont r -n t and !&

aand in b o t h s nd and c l a y e x e r t o p p o s i t e

i m p a c t s on s o i r pnysl-cal conolLions . 'Pheref o r e a s u i t a b l e

p r o p o r t i o n o f these are required f o r optimum s o i l t i l t h .

Thc low p o s i t i v e c o r r e l a t i o n between s u t u r a t e d h y d r a u l i c

c o n d u c t i v i t v and to ta l n n r o n i t v and t h ~ h i g h l y s i g n i f i c a n t

y d r a u l i c c o n d u c t i v i t y

because macro porosity

U I V L ~ : C I I L ~ I L I . U ~ , U U O I . O b l L V l n x l u P n c e s 1 1 ~ u r a u l i c c o n d u c t i v i t y

th:~( ; hytir;rlr l i c c o n d u c t i v i l . y

c a s e d ( T u b l c 131, thc:

r ~ q l u y b ~ g r u l ~ c ~ n ~ P O S L L L V ~ c o r r e l u ~ i o n between macro -poros i ty

u b n d u c t i v i t y f u r t h c r confirm Mbngwu e% al.

( , ,", , r rllurrAhu u r r u u r u w l d - p o r o s i ty have pronounced e f f e c t

i n Sou th e a s t e r n N i g e r i a n

s i g n i f j-carit negative

~ u l i c c o n d u c t i v i t y and

ras a n i n d i c a t i o n t h a t t h e

mjr-rn-rn m a r r r n . - n n r o s , ~ ~ rat.10 CUULJ. be used as an i m p o r t a n t

i2: d i s p o s a l o f sewage

&u\rtt. a r l u =+ +AUVIIbu brLF, uu u u r u ---auli c cor tduc t iv i t ;y

idex t o e v a l u a t e t h e e f f e c t o f long-term

\..A,..,. n - A - C r l ., -.- t n A- t h e n a f i l r s + r x d h v d ?

of these s a i l s .

; n i f i c a n t (PT 0.05)

564) between s a t u r a t e d

,, r e s p e c t i v e l y i n

w r s i o n ratios have

u n p l l c a x m n s Ior saturates n y u r a u l r c c o n d u c t i v i t y , i n f i l t r a t i ~ n

r a t e a n d the amount of w a t e r s t o r e d i n t h e s o i l when sswaEe

s l u d g e a n d e f f l u e n t n u r e used f o r a l o n g p e r i o d o f time,

Sumncr and IlcLaughlan (1996) and B a l k s e t nl. 11996) made

similar o b s e r v a t i o n f o l l o w i n g a p p l i c a t i o n s o f sewage e f f l u e n t s .

.ons were t h a t h i g h

I sewage e f f l u e n t s c a u s e d a n

-1 t o d i s p e r s e , which

1 h y d r a u l i c c o n d u c t i v i t y .

L p h y s i c a l and chemica l

p h y s i c a l p a r a m e t e r s

l i t y and h y d r a u l i c c o n d u c t i v i t y )

r ~ t t r r , ESP, S A H , ECe and

s a t c o n c e n t r a t i o n ) a r e snown i n l lnb le 14 . The re was a

s i g n i f i c a n t , ( P C 0.05), p o s i t i v e c o r r e l a t i o n ( r = 0.742)

between s o i l o r g c n i c m a t t e r and SAW and a s i g n i f i c a n t ,

( P 4 0.05), n e g a t i v e c o r r e l a t i o n (r E -0.672) between o r g a n i c

n a t t e r a n d a g g r e g a t e s t a b i l i t y i n t h e sewage s o i l . The

c o r r e l a t i o n between o r g a n i c m a t t e r and a g g r e g a t e s t a b i l i t y

,710) i n t h e non-sewage s o i l ( T d b l e 1 4 ) .

zat t e r and SAR

1 t o e l e v a t e d

~ V U L U C I concenI;ra UOII 1.n c n c : ;o i l , wn l c t l p r o b a b l y cou ld have

caused t h e obse rved n e g a t i v e c o r r e l a t i o n betwcnn s o i l o r g a n i c

m a t t e r and a ~ ~ r e a a t e s t a b i 1 i t . y . The e x p l a n a t ion is t h a t -- -

t h e d i s s o l u t i o n o f o r g a n i c m a t t e r

could have r educed t h e q u a l i t y af

serve ac ;?. b i n d i n g a g e n t i n t h e sc

s o i l , iricroclric i n ory:;~ni.c muttfir :

of t h e s o i l , which i~ i n a1:recrnen.

caused by sodium s a l t

t h e sewage m a t e r i a l s t o

351. But i n t h e non-sewage

t with t h e xxxdg s t u d y o f

Mbagw e t a l . (1991). The e x p l a n a t i o n i s that abundance

o f h i z h a u t l l i t v o r p a n i c matter i n t h e s o i l c o u l d a c t as a

i e s and sa l t

c o r r e l a t i o n s

z c t i v e l y ) , w i t h

s u g g e s t i n g t h a t

nf il t ra t i o n , h y d r a u l i c

r e q u i r e s p r a c t i c e s

c s of ESP, S A H ,

s t i o n s i n t h e s o i l .

ased c l a y d i s p e r s i o n

o i l p h y s i c a l ,

s a s s e r t i o n a g r e e s

.-. 68 T a b l e 14 ; - . -C~r r .~ l a t ion -between. .some p h y s i c a l a n d -chemical p r o p e r t i e s - o f . . t h e - s o i l . - - .

. . . . . . I . - . - - - , . . , . I - + . . . . . . _ . . . . . . . . . . .,;, ,,,3.J.,. : . . C d r r i i a t i o n Xoef f i c i e n t (r a , . i . . - . . . . . ... ~ o i I / ~ a r a m e t e ~ r _ ---aI - ,

- --- ... . - - - . -DR - ESP . . SAR EC e S a l t Conc MWD - -&----------- . --- . . . . . . . .

. . . . . - , .- - - -, . - _, - . . -

iqimho6 cm-I (mg 1:') .....

( F.m hr-I Y . .- - . - ,,I' . ._

Sewage S o i i

. . on Sewage $ o i l (N15)

OM (%I - 1;-0

DR - -0.489"' I .O

ESP 0 .184"~ 0 . 5 2 7 ~ " 1 .O

SAR 0.443"" 0.472"' 0.742"' 1 .O

ECe (mmhds cm'l) 0 . 4 9 4 " ~ 0.185"" 0 , 6 2 4 " ~ 0 . 5 5 6 ~ " 1 .0

* * S i g n i f i c a n t a t P 0.01

S i g n i f i c a n t a t P 0.05 ds Hon s i g n i f i c . a n t .

011 , O r g a n i c m a t t e r

ESP Exchangeable sodium p e r c e n t a g e

SA3 Sodium a d s o r p t i o n r a t i o

E6e E l e c t r i c a l c o n d u c t i v i t y

KdD Kean weight d i a m e t e r

BR ~ i s ~ e r s i o n r a t i o . -

Ex' S a t u r a t e d h y d r a u l i c d o n d u c t i v i t y .

t n a t u x o o l v e d sa l ts , p a r t i c u l a r l y sodium, a p p l i e d t o t h e

m i l t h r o u g h r;cw;4gc r ; l u d g t ? und e f f l u e n t s tli:;por::cd s o i l

, and r e d u c e d w a t e r

i f i c a n t , p o s i t i v e

s o i l .

r s i b i l i t y

e r a n d s a t u r a t e d

and 0.114) i n t h e

, suggesting that f a c t o r i l y t o

. v i t y o f t hese s o i l s .

1rauli.c conductivity

!d, which was

al . (1996) and

o r g a n i c materials

d i e conductivity

~ r r e l n t i o n existed

R , e l e c t r i c a l c o n d u c t i v i t y and

g t h a t i n c r e a s e

t u r a t ed h y d r a u l i c

t e b h y d r a u l i c

uunuucz1v1Cy 1s a measure or 11,s c o n c r l o u t i o n t o infiltration

f l o w and i s i n f l u e n c e d by p o r e s h a p e s , d i s t r i b u t i o n , and

c o n n e c t i v i t y , i n c r e a s e i n c l a y d i s p e r s i o n caused by a n

c o i l can a f f e c t port: r ;hupes , di: ; t r i b u Lion, and c o n n i x c t i v i t y

which will c o n s e a u e n t l y a f f e c t t h e s a t u r a t e d h y d r a u l i c

l d i n g c a p a c i t y and i n f i l t r a t i o n r a t e

sk o f r u n o f f and s o i l eroci.on. T h i s

r e s u l t s o f White (19881 on t h e

q u c u ~ ~ ~ i r c a ~ ~ o n s oz ~ u l a g e p r a c t i c e s and s o i l h y d r a u l i c

p r o p e r t i e s where in p o r e s i z e s , shapes a n d c o n n e c t i v i t y

i n f l u e n c e t h e h y d r a u l i c p r o p e r t i e s of s o i l s .

4.7 Csrbon Dioxide E v o l u t i o n

The cumulative C02 e v o l u t i o n of t h c t o p mi l i l lhd

s u b s o i l o f t h e s t u d y s i t e s is shown i n Fig. 3. EIigh m i c r o b i a l .

respiration r a t e s were r e c o r d e d f o r t h e tap 0-30 cm s o i l o f

f rom t h e f i r s t up t o t h e n i n t h week,

l a c s c a T l n g cnnc o r g a n i c m a t t e r i n t h e t o p 0-30 cm s o i l o f

t h i s area w a s still unde rgo ing r a p i d decompos i t i on . The v e r y

r 0-30 cm and 30-60 cm d e p t h s of

30Cm and

30-60 c n d e p t h of t h e sewage s o i l ( F i g . 3 ) suggest t h a t

o r g a n i c m a t t e r a t t h e s e d e p t h s a r e more o r less s t a b l e ; o r

t h a t r ~ i c r o b i ' n l b iomass d e c r e a s e d w i t h dep th .

The f a c t that some of t h e organic compounds i n sewage

r l u d g e a r e more b i o - d e g r a d a b l e ( and supposed ly more

o f m i c r o b i a l . sewage s o i l .

~ y l e and Paul

(1989) t h a t t h e i n i t i a l r a t e s of decompos i t i on of sewage

s l u d g e were , qene ra l ly f a s t as t h e r e was n f l u s h of b i o l o g i c a l

a c t i v i t y , b u t t h a t t h e m i c r o b i a l b iomass l a t e r on d e c r e a s e d

as t h e e a s i l y degradable m a t e r i a l s and t h e m i c r o b i a l m e t a b o l i t e s

were m i n e r a l i z e d .

The i m p l i c a t i o n s o f such h i g h ~ a t e s o f C02 e v o l u t i o n s

i n t h e sewage t o p s o i l a r e t h a t i t c o u l d b e d e t r i m e n t a l t o

' s o i l f e r t i l i t y because o f t h e r a p i d m i n e r a l i z a t i o n o f t h i s

pli of t h i s s o i l .

Ayuso e t al. (1936) s t u d i e d t h e e f f e c t s o.f plI on t h e

s o l u b i l i t y of CG2 j n d o b s e r v e d t h a t i nc r ea sed solubility of

at low pH had a rnajor n e g a t i v e i n r l u e n c c OIL t h e r h t e s of - 2

p h o t o s y n t h e s i s , availability o f ammonium a n d p h o s p h a t e ,

gL .,..w.A o f micro-organisms and t h e m o b i l i t y o f heavy

I were toxic t o mic ro -o rgmisms .

Pecal c o l i f orms r e p o r t e d i n

? d i n g t h e Un i t ed S t a t e s

nnvl Pnnrncrnfs 1 W r n i - a m t i nn A m a n m ~ r (TTSRPA 1 OO? \ c f n n r l ~ r r l c and -- - -*-.nrrrr r-s - s v U V " us"., ..grr..uJ \---* .r, . ,,, , " " - I I U U & U"

s u g g e s t i n g that t h e t y p e of t r e a t m e n t g iven t o t h e s l u d j

' l j r i o r t o d i s p o s a l on land can be t h e ma jo r c o n t r i b u t i o n

f a c t o r . Sewage s l u d g e s t a b i l i z a t i o n p r o c e s s e s have beel n

s u g g e s t e d f o r s u b s t a n t i a l r e d u c t i o n i n pa tnogen numbers i n

sowage cludgc and c i l ' l u e n t s.

Although t h e s e o rgan i sms can e a s i l y d i e o f f w i t h t i m e

i n t h e s o i l sys t em and c o n t r i b u t e t o t h e s o i l o r g a n i c

m a t t e r ,

a f t e r a n a e r o b i c d i g e s t i o n ( T a b l e 1) s h o u l d b e a p p l i e d t o

% * r i c u l t u r i l l l a n d . The f a c t b e i n g t h a t they may e n t e r i n t o

interactinns i n t h e s o i l system, which can r e s u l t i n overall

3n other mi.crobia3 p o p u l . s t i o n s , s o i l

a b A VAA,.., , ,.,- ,,;int growth, o r t h e y m a y c o n t m ~ i . n a t e c r o p

1.-dcpl c t i n g crop)

1.d i rl,; c r o p ) U S C ~

:'. 4. N t t i xe

0.05) in tlic . '

( T a b l e 15).

s o f t h e maize

11 as d i f f i c i e n c y

U.Y I U U kuua UI I I I I, L . U Y . F ~ ~ I arlu u ~ ~ o s u r ~ u r . u a as r e c o r d e d b~ visual

rnbnra groundnut ( V i c n a bterranen) wage Non-sewage t - c u l o i l s o i l

- Sewage soil

1 il b ~ . f ' o r c lc;lcl~lrl l l ; cun be

.It concentrations in the '

h may have been detrimental

v v RIvnrli U ~ ~ I ~ L U U L C I Y.IUUUU~IUL but not dolrhnental tr,

riza and bambtira

;oil salinity, which

of Bernstein 11964) .

! to s o i l s a l i n i t y

; h a t l o n e - t erm

:c and effluents

~ n t can tolerate tho

;her toxic and/or

; h a i r u o o cihould be

)r the availability

.. ..,,,, ,, ,,,,.. ,.., ,,,, -1 e x c e s s salts.

e re n o t sir:nif i c a n t l y

e a r r e l a t i o n a n a l y s i s showed

p o f i i t i v c c o r r e l a t i o n (r=0.176 and

hydraulic c o n d u c t i v i t y a n d t o t a l

non-sewage s o i l s , r e s p e c t i v e l y .

hydraulic c o n d u c t i v i t y a n d p o r e E

s i g n i f i c a n t l y ( P < 0.01), h i g h pc

for m a c r o - p o r o s i t y and h i g h l y nee

e r , c o n t e n t , t o t a l N ,

s maize pe r fo rmance wore

term d i s p o s a l o f sewage

s l u d n e a n d e f f l u e n t s i n t h e s o i l . Heavy m e t u l s ( ~ n , Cu, Pb,

u l a t i o n s and e l e v a t e d s a l t c o n c e n t r a t i o n s and

u c p - u a i l ~ l o n of t h c s o i l p h y s i c u l c o n d i t i o n o w c r c ! t h o a d v c r s c

a non-s igni f ic : in t ( P a 0.05)

I 0.225) between s a t u r a t e d

p o r o s i t y i n t h e sewage and

C o r r e l a t i o n s between s a t u r a t e d

i i z e d i s t r i b u t i o n showed a

I s i t i v e c o r r e l a t i o n ( r=0 .979)

~ a t i v e c o r r e l a t i o n (r= -0.906)

;y r a t i o o n . s a t u r a t e d

n a l ~ n l l l c a n ~ nneaLlvn c o r r e l a t i o n a l s o e x i s t e d between

i n the sewage s o i l

down and o r g a n i c

1 were s i g n i f i c a n t l y

t t e r i n t h e sew&e

vvlLbrunAvrLo u r a ~ n from t h i s s t u d y are that:

(i) Long-term d i s p o s a l of sewage s l u d g e . a n d e f f l u e n t s o n t o a

sandy s o i l improved t h e t o t a l s o i l o r g a n i c m a t t e r , t o t a l N ,

exchangeable b a s e s , c a t i o n exchange c a p a c i t y and s u p p o r t e d t h e

growth and y i e l d s of maize,

(ii) These was tes c l e a r l y have detrimental e f f e c t s on t h e

growth and y i e l d s of leguminous crops. T h u s , t h e growth of t h e

Bambarn groundnut (v igna s u b t e r r a n e u ) wuc u n s u s t a i n n b l e u n t i l

t h e sewage s o i l was l e a c h e d of e x c e s s sa l t .

(iii) IIeavy metals (Bn, Cu, Pb, and Cd) accumulat ion, h i g h

sa l t c o n c e n t r a t i o n s , degradation o f t h e soil p h y s i c a l c o n d i t i o n s

and hi13:h rnicx-obiol r c t ; p i r u t i o n urc t h c 1 i r n i t ; i t l l : 1':ac t o r o t o

xiul and g e n e r a l i z e d agronomic u t i l 3 z a t i o n of

q n r l a f f l * * a n t e Tharr-fnve it, long term d i a p o s A

l t i o n c t o l a n d d i o p a s a l

Ludge and e f f l u e n t s

e s t h a t can be used t o

o r o t h e r wunte

i n t r e s e a r c h approaches

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. . . Mbagwu, J.S.C. and P i c c o l o , A. (1990). Carbon, n i t r o g e n , and phosphorus c o n c e n t r a t i o n s on a g g r e g a t e s of o r g a n i c waste-amended s o i l s . Biol . Wastes. 31:97-171.

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Nciean, E.O. (1982). S o i l pH and l i m e requi rement . I n : A.L. Page ( e d , ) . Methods o f S o i l A n a l y s i s , P a r t 2 , 2nd ed. Agron. Monogr. 9. ASA and SSSA, Madison, WI pp. 199-224.

Metzger, L. and Yaron, B. (19871. I n f l u e n c e of s l u d g e o r g a n i c m a t t e r on s o i l p h y s i c a l p r o p e r t i e s . Adv. S o i l S c i . 7: 141-163.

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a 1 p r o p e r t i e s 5a. S o i l Sc i .

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C1970). E f f e c t of . pH on soil. n i t r o g e n

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composks on s o i l p o r o s i t y and a g g r e g a t i o n , Qual. 10:556-561.

P a g l i a i , M,, and Antisari, L.V. ( l993) . I n f l u e n o r g a n i c m a t t e r on s o i l micro and macro s t r u Bioresource Technol. 43 :205-213.

Pagliai, M, and DeNobil i , M. (1993) . R e l a t i o n s h s o i l p o r o s i t y , r o o t development and s o i l en i n c u l t i v a t e d s o i l s , Geoderma 50: 243-256.

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ct? of was te c t u r e .

i p s between zyme a c t i v i t y

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Pojabok, T. and Kay, B.D. (1990). Assessment o f a combination of w e t s i e v i n g and t u r b i d l m e t r y t o c h a r a c t e r i z e t h e s t r u c t u r a l s t a b i l i t y of moist aggrega tes . Can. J o S o i l Sc i . 70:33-42.

Richards , L.A. (1957). S o i l Moisture. USDA Year Book, S e p e r a t e 49-60.

Robertson, W.R.; L u t r i c k , M.C. ; a n d Yuan, ToL. (1982). Heavy a p p l i c a t i o n of l i q u i d - d i g e s t e d s l u d g e on t h r e e u l t i s o l s 1 E f f e c t s on s o i l chemis t ry , J. Environ. Qual . '1 1 :.278-282.

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( s t a t i s t i c s New Zealand: el ling ten) . S t r a u b , P.M. , Pepper , T.L. , and Oerba, C.P. (1993). Hazards

from Pa thogen ic micra organisms i n l a n d d i s p o s a l o f sewage s ludge . Rev. Environ. Contam. Toxic 132:55-91.

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T i n r k s , A.E., Mazuruk, A.P. and Chesnin , LI (1974)- p h y s i c a l

and chemical p r o p e r t i e s of s a i l a s s o c i a t e d w i t h heavy . . a p p l i c a t i o n s of manure f ram c a t t l e - f e e d l o t . S o i l S c i .

- Soc. Aaer. Proc. 38:8;26-830.

T e s t e r , C.F. (1990). Organic amendments e f f e c t s on p h y s i c a l and chemical p r o p e r t i e s of a sandy s o i l . S o i l Sci . Soc. Aaer. J. 54: 827-831.

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USSLS (U .S , S a l a n i t y Laboratory Staff Manual) and Improvement of Saline and A l k a l i Soi2 Handbook, Washington, D.C.

, S o i l Survey S t a f f . , Govt . P r i n t i n g

( 1 9 9 3 ) ~ 40 CFR. ~ s a l of sewage zgton, D.C.

, (1969). Diagnos i s Ls. USDA Agric.

Vomocil. J . A . (1965). P o r o s i t v . In: C.A. Black (ed.) Methods : 299-374.

: o n d i t i a n of a ry p o u l t r y t34-440.

t r a u l i c ; N a t i o n a l S o i l , ) , Aust. Soc.

effects of ; o i l structure.

modera t e , medium s u b a n g u l a r b l o c k y ; v e r y

f r i a b l e , s l i g h t l y s t i c k y , s l i g h t y p l a s t i c ;

v e r y few r o o t s ; few, medium p o r e s ; d i f f u s e

boundary . Bt 2 105-160 crn Reddish brown (2.5 YR 4/61 ; Sandy loam;

modera t e , medium subangular; f r i a b l e ;

s l i g h t l y s t i c k y , s l i g h t l y plastic; few

medium p o r e s .

SOIL PROFILE DESCRIP ' I ' IOIJ

P r o f i l e No, S/NSK/~

FAO/UNESCO: F e r r i c L i x i s o l

S o i l c l a s s i f i c a t i o n : USDA: A r e n i c Kandi u s t u l t s

L o c a t i o n : U n i v e r s i t y o f N i g e r i a , Nsukka, w i t h i n t h e sewage

d i s p o s a l s i t e , a b o u t 2 rn from t h e o x i d a t i o n pond.

17/2/99 Data d e s c r i b e d :

D e s c r i b e d by : B.E. Udom

Topography/Slope: G e n t l y s l o p i n g (4-8%)

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a n d c a s s a v a

Climatc: Hun~id t r o p i c s

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b i s t u r e C o n d i t i o n : Moist

( A l l c o l o u r s a r e m o i s t u n l e s s o t h e r w i s e s t a t e d )

B r i e f D e s c r i p t i o n o f t h e P r o f i l e

Deep, somewhat e x c e s s i v e l y d r a i n e d ; v e r y dark r e d d i s h brown

t o r e d d i s h brown. Sand t o s andy loam. Accumula t ion o f hurnif ied

sewage m a t e r i a l s i n t h e Al3 h o r i z o n ; c l e a r l y d e f i n e d

h o r i z o n a t i o n , s a l t a c c u m u l a t i o n e v i d e n c e a t t h e 89 cm d e p t h ;

r o o t d i s t r i b u t i o n normal b u t c o n c e n t r a t e d i n t h e t o p 25 cm dep th .

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I, medium r o o t s . '

YR 3/4) loamy s a n d ;

ular; l o o s e , non

ny fine t o medium

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