G. Sanjari, H. Ghadiri, C. Ciesiolka

Research Institute of Forests and Rangelands, Tehran, Iran

School of Environmental studies, Griffith University, Australia

Department of Natural Resources and Mines, QLD, Australia

Short term intensive rotational grazing in native pasture: Effects on

soil nitrate and extractable P

Outline

IntroductionCurrajong project

Location and climate Grazing treatments Soil analysis Results

Soil Organic Carbon and Nitrogen

Soil nitrate and extractable P Sheep camp results

Conclusion

Introduction

Livestock industry is of main sources responsible for downstream water pollution

Introduction (continue)

• The maximum concentration of nitrate allowed in drinking water is 10 mg/L.

• For aquatic life, nitrate level more than 4 mg/L considered as pollution problem

• Biological growth can be stimulated when Dissolved reactive P (DRP) exceeds 0.01 mg/L

Standards for the pollutants

In soil solutions:

In water:

• Environmental concern arise when the nutrient level in soil profile exceed 160 kg/ha for nitrate and 330 kg/ha for available P

Introduction (continue)

Grazing behavior and animal waste concern in native pasture

• Recycle 75 – 85% of forage they consume• Don’t graze pasture uniformly• Distribute deposits mainly around food

and water troughs, under shades, along fence lines, etc

Grazing animals:

Outcomes of a continual grazing:• Imbalanced distribution of nutrients• Nutrient depletion across paddocks• Low pasture productivity• Animal camp site development and

environmental concern on water contamination

Sheep Camp

Introduction (continue)Grazing practices affect soil health and water quality

Continuous grazing (large paddock) • Increasing runoff and soil loss and low

productivity• Grazing animals are free to congregate• Encourages animal camp development

Rotational grazing (small paddocks)• Includes rest periods for pasture recovery

after grazing operations• Better runoff and soil loss control• Discourages animal congregation• More balanced distribution of animal

wastes

Currajong case study

Short term Intensive Rotational Grazing (SIRG) vs. yearlong Continuous Grazing (CG)

• Organic Carbon (SOC)• Organic Nitrogen (SON)• Nitrate-Nitrogen• Extractable P

Soil parameters:

the data

Queensland

Murray Darling Basin

CurrajongLocation:

Property of CurrajongSoutheast Queensland

31%

69%

Dry Season

Wet season

Oct

MarApr

Sep

Currajong study (continue)

Climate

Long term annual: 645 mmRainfall:

Soil:Up to 50 cm in depthBrown to dark clay loam

Vegetation:Open Eucalypt woodland withunderstorey of perennial grass species

Dominant species: Dichanthium sericem

Methods: Stocking properties36

530

3658

036

630

3668

036

730

3678

036

830

3688

036

930

3698

037

030

3708

037

130

3718

037

230

3728

037

330

3738

037

430

3748

037

530

3758

037

630

3768

037

730

3778

037

830

3788

037

930

3798

038

030

3808

038

130

3818

038

230

3828

038

330

3838

038

430

3848

038

530

3858

038

630

3868

038

730

3878

038

830

3888

0

02468

101214161820

Continuous grazing Short intensive rotational grazing

Sto

ck

ing

ra

te

DS

E/H

DDH- Number of dse days per hectare over the whole study period; ‡- Means ± 1SD; SR- Stocking rate

Grazing Grazing periods Rest periods SR DDH Treatments (days) (days) (dse/ha) dse.day/ha

Short intensive rotational 14 ± 9‡ (101 ± 60)‡ 12.6 ± 6 ‡ 3608

Continuous 365 0 1.6 ± 0.2 3529

Currajong study (continue)

Currajong study (continue)

Methods: Soil analysis

Soil Organic Carbon:Rapid wet oxidation (Walkley and Black)

Soil Organic Nitrogen:Semimicro Kjeldahl procedure (Bremner 1996)

Nitrate and Ammonium:2 M KCL solution extraction (Bremner Keeney 1966), auto analyzer (Lachat 2001)

Extractable P0.5 M NaHCO3 Orthophosphate extraction(Colwell 1963), colorimetric procedure (Murphy and Riley 1962)

Currajong study (continue)

Results: SOC & SON (treatments)

20.0

22.5

25.0

27.5

30.0

SO

Cto

n ne/

h a

Short intensiverotational grazing

Continuousgrazing

Notgrazed

2001 2006

ns

ns

ns

p<1

1.6

1.8

2.0

2.2

2.4

SO

Nto

nn

e/h

a

Short intensiverotational grazing

Continuousgrazing

Notgrazed

2001 2006

ns

nsns

p<29

p<25

Results: SOC & SON (sub-treatments)

Currajong study (continue)

SO

Nto

nne/

ha

C1 C2 C3 C4

3.0

2.5

2.0

1.5

1.0

Short intensiverotational grazing

Continuousgrazing

2001 2006ns

ns

ns

ns

p<18

C1 C2 C3 C420.0

24.0

28.0

32.0

SO

Cto

nne/

ha

Short intensiverotational grazing

Continuousgrazing

2001 2006

*p<10

ns

ns

n

1.5

3.0

4.5

6.0

NO

3-N

Kg/

ha

0.0

2001 2006

Short intensiverotational grazing

Continuousgrazing

Notgrazed

Currajong study (continue)

Results: Nitrate & Extractable P

Ammonium concentrationIn grazing exclusion:

2001 4.56 mg/kg

2006 13.69 mg/kg

0

10

20

Ext

rac

tab

leP

Kg

/ha

2001

2006

Short intensiverotational grazing

Continuousgrazing

Notgrazed

Currajong study (continue)

Results: Nitrate & Extractable P (continue)

0

400

800

1200

1600

2000

0 268 683 1047 1367 1737 1824

May 01 Days May 06

Massofresiduekg/ha

Short intensive rotational grazing

Continuous grazing

1000

1500

2000

2500

3000

3500

May 01 Feb 02 Mar 03 Mar 04 Feb 05 Feb 06 May 06

Date of samplingH

erb

age

mas

skg

/ha

Rotational grazing

Continuous grazing

Increase in herbage mass

Increase in Residue

Currajong study (continue)

Results: Nitrate & Extractable P (Sheep camp effects)

100

10

1

0.1

0.010 100 200 300 400 500

1000

100

10

1

0.1

Distance from sheep camp (m)

NO3 2001

PO4 2001

PO4 2006

NO3 2006

PO4concentration(kg/ha

in0-10

cm)

NO3concentration(kg/ha

in0-10

cm)

Sheep camp vegetation:

Couch grassAgropyron repense (L.) P.Beauv

Couch grass regrowth:

Herbage massKg/ha DM

Rest perioddays

2650 26

3685 60

Soil analysis:

NitrateKg/ha

PhosphateKg/ha

2001 126 222

2006 17.6 79.3

Thresholds 160 330

Results: Nitrate & Extractable P (Sheep camp effects)

Currajong study (continue)

Water analysis: Sampled on 22/01/06

NO3-N (Mg/L) 0.143 0.189 0.133 0.100

DRP (Mg/L) 0.062 0.013 0.137 0.141

Time (min) 6 15 25 34

Water analysis:Sampled in 2001

NO3-N 3.4 Mg/L

DRP 2.5 Mg/L

Conclusion

Continuous grazing encourages animal aggregation to develop camp sites with large deposits of animal wastes raising alarm for downstream water contamination

In the study area we found the above threat could be easily the case at regional scale with more camp site development under continuous grazing

Short period Intensive Rotational Grazing (SIRG) in the native pasture, modified the aggregation behavior of animals, leading to a major decrease in soil nitrate and extractable P concentrations

The rotational grazing provides an environmentally oriented pasture utilization giving a more forage production over continuous grazing