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FATE OF N-UREA IN TEA PLANTS AND TEA SOILS IN INDONESIA
Zuhdi Sri Wibowo*
ABSTRACS
FATE OF N-URKA IN TEA PLANTS AND TEA SOILS IN IHDONE5IA. A Serial research the
use of N-urea in tea plants in Indonesia has been conducted frJm 1982-1985. The N
urea was detected in tea plants of young stage and in the soils (AndoBol, Regosol,
Latosol, and Podzolik). The methods used in the researches were the conventional
measurements for N losses in the from of a gas and of solution, and a tracer tech
nique for naff in the soil profiles, in the whole plant part of young stage, and in
the pluckable leaves of production stage. The conclusions of the researches are as
follows: (1). In tea soils which have slightly acid reactions and rather high
organic matter content, fertilizations with urea did not undergo too much losa due
to volatilization and leaching Most of N-urea was lost as solution by run off when
it was applied by broadcasting or were still remained in the soil profiles. (2). The
Ndff for young unproductive tea plant was very much influenced by the prillling
effect and soil characteristic which enhance the better growth of roots. The condi
tion in which tea plant roots are growing vigorously, the competition of N-use in
the soils is won by against plant soil microorganisms. (3). Ndff in the tea plants
of early productive stage has been distributed about 70 ~ in leaf part and about 30
~ in wooden part. (4). Time interval between two succassions of the fertilizer gift
on productive tea plants using urea is better done at every 2,5 - 3 months. (5). The
Ndff of tea plants of 6 - 15 years old has bean characterized by strongest uptake
and slightest dilution effect.
AB..cJTRAK
ALUB N IJ1lBADALAtt TANAItAN TO DAN TAMAR-TAMAR TIm Dl IHDONBSIA. Suatu seri
penelitian tentang penggunaan N-urea pada tanaman teh dan tanah-tanah teh di Indone
sia telah dilaksanakan dari tahun 1982-1985. N-urea telah dirunut dalaJII tan8Jllan
belum menghasilkan maupun yang menghasilkan serta di tanah-tanah teh (Andosol, Rego
sol, latosol, dan Podzolik). Metode yang digunakan meliputi metode pengukuran kon
vensional untuk penelitian kehilangan N dalalitbentuk gas dan larutan pupuk, dan
metode perunut untuk mengukur Ndp dalsm profil tanah, dalam seluruh bagian tanah
belum menghasilkan, dan dalam pucuk petikan tanaman menghasilkan. Beberapa kesimpul
an yang diperoleh adalah sebagai berikut : (1). Pada tanah teh yang bersifat se
dikit masam dan mengandung bahan organik lebih tinggi, kehilangan pupuk N-urea dari
* Pusat Penelitian Perkebunan, Gambung
257
proses penguapan dan pencucian tidak besar. Kehilangan N-urea yang paling besar
adalah berbentuk larutan pupuk dalam air li.pasan (run-9ft) terutama apabila pupuk
diberikan secara disebar, atau yang tetap terlinggal di dalam profil tanah. (2).
Besarnya Ndp yang diserap oleh tanaman belum menghasilkan sangat dipengaruhi oleh
proses stimulasi dan sifat tanah yang mendorong pertumbuhan altar menjadi lebih baik •
.Akar tanaman teh yang tumbuh dengan baik altan menyebabluin menang dall1lll1t0000petisi
penyerapan N dengan mikroorganisllle tanah. (3). Penyerapan Ndp oleh tanaman beltBI
belum menghasilkan didistribusikan sekitar 70 % Ite bagian daun dan sekitar 30 :!Ii:nya
lagi ke bagian berkayu. (4) • Interval waktu pemberian pupuk urea pada tanaman
menghasilkan sebaiknya setiap 2,5 - 3 bulan. (5). Penyerapan Ndp pada tansman 6-15
tahun adalah yang paling kuat dan paling kecil pengaruh pengencernn hara di dalam-
nya.
INTRODUCTION
Urea has been dominantly used for tea plants in Indonesia since
about 1970, and therefore very seldom substituted by other N ferti
lizer. Formerlly sulphate of ammonia (SA) was very preferable to be
used in estate crops including tea, but since urea has been produc
ed in Indonesia quite excessively and it can be bought under subsidy
price of the Government, the use of urea has be come almost a single
source of N. The situation was also enchanced by the temporary con
clusion of an experiment mentioning that no agronomic effect had
been showed between urea and SA (1).
The attention of tea planters towards urea actually limited on
the response of tea plants in form yeald ha -1 and not on the fate
of urea after it is applied into the soils and in the plants. This
paper is dealing with the results of the research works of urea in
Indonesia tea soils and tea plants which were serially conducted by
RITC Gambung. All of the informations presented here are aimed to
provide a data base, which is presumably useful for urea technology.
RESEARCH ON UREA USING CONVENTIONAL METHOD
Loss of N in Gas For.s. Nitrogen gases in the forms of NH3, N2,
N20, NO, and NOx which escape from urea after being applied into teasoils heve been observed during 15 days. Four types of soil, i.e.
Andosol, Regosol, Latosol, and Podzol ic of 0 .- 20 cm in depth were
put in plastic pots and than urea was applied with an equal rate of-1 -1100 kg N ha and 200 kg N ha. • The experiments were aimed to
258
study the effects of soils moisture, fertilizer placement, and N
rate on (a) the loss of N in NH3 gas and (b) the loss of N in other
gases presumably N2 + N20,+ NO + NOx'
The experiment on NH3 volatilization was conducted at laborato
ry using a closed system aparatus of one way air flow according to
FENN and KISSEL (2). The results of the observation is presented in
Table 1.
Table 1. Effects OV fertilizer placement, soil moisture, and
fertilizer rate on NH3 volatilization in four typesof tea soil (3)
NH3 gas in soil ofTreatment
Andosol Regosol Latosol Podzolic
-1-------------Kg N ha ---------------
Fertilizer place.ent broadcast
9.18.89.99.2
dibbling 5 cm
5.45.78.39.6
Soil .oisture
half sutarated
6.94.99.016.0
saturated
7.69.69.22.7
Fertilizer rat~1
3.02.21.62.1
100 kg N ha_1200 kg N ha
11.512.316.616.2
The pH of soils lays between 5.4 and 5.9,and the soil structur
es are crumby, its clay contents vary between 26.2 and 76.4 %. These
soil characteristics have caused a small amount of NH3, volatilizati
on, especially when urea was applied by dibbling of 5 cm in depth.
The Table 1 also shows that NH3 volatilization of 200 kg N ha -1 is
3 to 4 times higher than that of 100 kg N ha-1•
The loss of N in another gas forms excluded NH3 have been com
puted by substraction of the loos of total N minus the loos of NH3in each treatment. The loos of total N was known after the pots had
been taken from the field during 15 days. The pots were placed in
259
field condition under tea bushes. The results of the subtraction is
shown in Table 2, in which the gas formed were assumed as N2, N20,
u~, and un . According to PI~n~~ln~~l J L these gases are tormedxwithin the processes of NH02 self dissociation and denitrification.
Table 2. Effects of fertilizer placement, soil
fertilizer rate on the loss in N gas
ed NH3) in four types of tea soil (3)
moisture, and
forms (exc1ud-
Other N gases excluding NH3 in soil ofTreatment
Andosol Regosol Latosol Podzolic
-1-------------Kg N ha ---------------
Fertilizer placements broadcast
11.815.912.515.5
dibbling 5 em
16.612.310.54.7
Soil aoistureshalf sutarated
10.515.712.82.1saturated
13.012.010.118.1
Fertilizer rat~r
11.0
15.19.610.2100 kg N ha_1
200 kg N ha
12.413.111.810.1
Nitrogen losses in the forms of other gases were almost similar
in all types of tea soil, due to the soil characteristic which•caused the similard yields of HN02 self dissociation plus denitrifi-cation. In Podzolic soil under saturated condition (sand content 44
X), the N loss became quite large presumably because of denitrifi
cation.
The Lost ,of N in Solution Forms. In tea growing areas which are
characterized by high rainfall and hilly landscape, the loss of N
from urea in solution from by run off water is highly possible to
occur. The urea solution transported in the run off water occured
when there was excessive rain fall soon or only few days after fer
tilizer application. The amount of N from urea in run off water
during 20 times rain fall after fertilizer application is shown in
Table 3.
260
Table 3 presents a summarized result of two experiments which
sited Andosol and Latosol. At Andosol the experiment was located
under 32 % covered by canopy and at Latosol was located under 90 %covered.
Table 3. The lost of N from urea in the solution from transported by
run off water during 20 times of rain fall after fertilizer
application at Andosol and Latosol (3)
Metods and rateof fertilizer
*Andosol
N total N fertilizer
Latosol **
N total N fertilizer
-1---------------------kg N ha ----------------
Nin fertilized
329.5-99.2Broadcast, -1
387.558.0 (58%)178.379.1 (79%)100 kg N ha
Dibbling, -1347.5
18.0 (18%)168.569.3 (69%)100 kg N haBroadcast,200 kg N ha-1
491. 3161. 8 (80%)210.1110.9 (55%)
Dibbling, -1361. 0
31.5 (15%)183.384.1 (42%)200 kg N ha-------------------------------------------------------------------
*Notes :** slope 30% and canopy cover 32%
slope 25% and canopy cover 90%
The loss of N from urea by run off water wa lesser in Andosol
which has corser texture and higher organic matter content than in
Latosol which has finer texture and lower organic matter content.
Broadcast application of urea resulted a higher risk of N loss than
dibbling application, howevet the higher covering of canopy in this
case did not reduce the loss of N. The later might be explained that
the amount of run off water is more functioning as it was observed
at Latosol.
261
\
RESEARCH AND UREA USING 15N TRACE TECHNIQUE
The Loss of N in Leachage ~ater. The urea with 10 % 15N atom
excess was applied on young tea plants of 10 to 16 month old. The
vegetative propagation of clone TRI 2025 were transplanted into pots
(size 30 by 30 by 60 cm) in which had been filled up with 4 type of
tea soil profile i.e. Andosol, Regosol, Latosol, and Podzolic (Table
4).
Table 4. Physical, che.ical, and mineralogical characteristics of four Indonesia tea soils
*Andosol )
*Regoso 1 )
*Latosol )
•Podzolic )
Soil characteristic ---------------- --------------- ----------------
o - 20 20 - 60 0 - 30 30 - 60 0-20 20-40 40-60 0-20 20-40 40-60
Ch_ical
pH (H20)(KCL)
C Organic (%)
P205 avail (p~lCIC (m•• 100 g )-1Ca (•••• 100 II )-1KII ( •• e 100 II )-1K (•••• 100 II )-1Na (•••• 100 II )
5.8
5.5
5.76
6.3
21.4
8.0
1.4
0.5
0.2
5.8
5.4
4.36
5.1
22.4
8.3
1.4
0.4
0.4
5.6
5.2
4.60
4.6
18.2
6.2
0.6
0.8
0.2
5.9
5.4
4.03
3.8
18.1
5.7
0.5
1.0
0.2
5.5
5.1
2.33
3.8
13.6
5.1
1.4
0.4
0.1
5.0
4.6
2.13
2.6
10.8
2.1
0.6
0.2
0.2
5.5
4.6
1.0
2.3
9.0
1.5
0.4
0.1
0.2
5.6
5.3
2.72
9.0
9.1
3.6
0.8
0.4
0.1
5.4
5.0
2.81
5.9
10.7
3.4
0.8
0.3
0.1
5.4
5.0
1.183.6
6.3
1.3
0.3
0.2
0.1
Physical
Sand (%)
Silt (%)
Clay (%)
Density (g
Water cont.
-3~)
1/2 sat.
12.0
61.8
26.2
0.64
10.3
50.6
39.0
0.63
15.7
47.1
37.2
0.72
15.4
48.6
36.0
0.76
1.9
21.6
76.4
0.86
1.7
23.5
76.8
0.87
2.1
17.8
80.2
0.90
44.2
9.846.0
0.93
44.2
13.6
42.2
0.97
46.2
8.8
45.0
1.04
(%) 53.8
Water cont. sat. (%) 107.6
49.8
99.7
40.8
81.733.4
66.9
Mineralogical
Amorfic
Kaolini tic
Haloisite
Quarsite
Cipsite
......
H(+)
• "t •
H(+)
+t .••
(+ )
..•....
(+)
+
HH HH
(+) (+) (+)
+t .•.••.•• +
C+) (+) (+)
According to Soil Toxonomy (USDA, 1975). The soil afe belongs to Hydric Dystrandepts, Entic Dys
trandepts. Typic Haplohumox, and Sombritropepts, respec
tive
262
The N derived from fertilizer (Ndff) which exist in theleachage water, in the soil profiles, and in the plants were comput
15ed after the N assay the samples.
In this part, the Ndff' in leachage water collected during 6
months after urea application is summarized in Table 5. The Ndff
total is the sum of NH4+ and N03 - and it is supposed to be Ndffwhich leached down by rain water.
Table 5. Effect of soil type and N rate on the leaching losses of
Ndff as N03- and NH4- forms (3)
N in leachage waterSoil type
N
Rate NH +4 N total
-1--------------------- kg N ha ------------------------
33.3
9.600.162.281.6Andosol 66.7
24.28 0.205.624.10
33.33
7.280.161.761.25Regosol 66.7
20.06 0.264.733.50
33.3
3.730.211.000.75Latosol 66.7
11.6 0.262.692.10
33.33
6.300.171.551.10Podzolic 66.7
15.05 0.383.382.80
There is a clear differenge of Ndff in leachage water of ahigher N rate, although the effect among the soil types with thesame N rate have shown a similarity. From Latosol which has finer
texture, the Ndff in leachage water is lesser than the other soiltypes.
N Derived Fro. Fertilizer He.ained in Soil Profiles. In this
part, the amount of NQff which remained in the soil profiles 6 monthafter fertilizer applIcation is presented in Table 6. The soil profiles of 60 cm in depht were divided into 3 similar compartments
(i.e. 0 - 20 cm, 20 - 40 em, 40 - 60 cm) and the Ndff distribution
was distinguished as the exchangable form (i.e. N03 and NH4+) andthe non exchangable form (i.e. presumably an organic form).
263
Table 6. The amount and
tea prof ile of
application (3)
the distribution of Ndff in four types of60 em in depth, 6 monfns after fertilizer
-----------------------kg N h -1a ---------------------
-Andosolo - 20 em
20 - 40 em
40 - 60 em
-Regosolo - 20 em
20 - 40 em
40 - 60 em
-Latosolo - 20 em
20 - 40 em40 - 60 em
-Podzolieo - 20 em
20 - 40 em
40 - 60 em
10.12
9.49
5.1824.79
13.05
5.04
1. 5519.64
6.59
5.18
4.6216.39
12.8
6.14
0.86
19.8
0.29
0.07
0.140.50
0.36
0.20
0.23
0.79
0.222.22
5.10
7.54
0.21
0.03
0.06
0.30
10.41
9.56
5.32
25.29
(75.9)
13.41
5.24
~10.43
(62.3)
6.817.40
9.7023.93
(71. 8)
13.01
6.17
0.92
20.10
(63.3)
10.18
23.71
17.02
50.91
10.61
20.31
11. 6342.55
10.40
11. 0219.5941. 01
22.33
12.79
8.31
43.43
0.44
0.22
1. 922.58
0.40
0.68
2.87
3.95
0.27
2.4113.49
16.17
0.13
0.12
0.16
0.41
10.60
23.95
18.94
53.49
(80.3)
11. 0720.99
14.50
46.50
(69.80)
10.67
13.43
39.08
57.18
(85.8)
22.46
12.91
8.47
43.84
(65.8)
Notes: () is the ratio of Ndff to N rate multiplied by 100 %
In the Table 6. there are some important conclusions can be
withdrawn i.e. (1) most of the Ndff still remains in the soil
profils, (2) the remaining N is presumably in the form of organic
matter, (3) in the Latosol which has high clay content, the exchang
able Ndff is still quite large, especially at the depth of 40 - 60em, (4) strong, competition presumably has occured between the up
take of N by plants against the transformation of N by soil micro
organisms (Table 7).
264
Nitrogen Uptake Unproductive Tea. Pla.nts. The amount of Ndff
which was taken up by unproductive tea plants here is still of
partial observations reported in the two previous chapters. The
distribution of Ndff into plant parts can be seen in Table 7. In
unproductive tea plants that had been fertilized with N since the
beginning, the amount of Ndff each soil type has been quite clearlydifferent.
Table 7. Effects of N rate and soil type on dry matter, plant Nand
Ndff of unproductive tea plants at 16 months old (3)
Soil typeN rate and yield --------------------------------------------------
----------------------kg N h -1a ------------------
Dry .atter -1
-33.3 kg N ha_1-66.7 kg N ha
Plant N
-33.3 kg N ha=~-66.7 kg N ha
N~n.3 kg N ha=~-66.7 kg N ha
Andosol
253.0
211.7
3.76
3.20
2.23
2.24
Regosol
674.0641. 8
9.35
9.89
6.19
6.83
Latosol
532.2
381.7
7.57
5.66
4.77
4.05
Podzolic
878.0
1338.6
11.02
22.34
7.71
17.7
The larger amount of Ndff in tea plants planted on Rregosol andPodzolic due to the priming effect is the better soil characteris
tics for roots growth. The better the root growth is the large the N
uptake from fertilizer, in Table 7, for Regosol and Pozolic one can
observe the occurence of N uptake competition between tea plants and
soilmikroorganisms.
Unproductive tea plants fertilized with N in rather excessive
rate, the uptake of N have been mostly derived from fertilizer.
From Table 7, the Ndff of unproductive tea plants vary from 53 %for the soil with high organic matter content (Andosol) up to 70%
for the soil with low organic matter content (Podzolic). The harder
265
competition of N uptake between tea plants and soil microorganisms
likely occur in the soil organic matter content.
Nitrogen Uptake by Tea Plants at Early Production Stage. The
tea plants used here were just at the early stage of production Ithat was about after 10 months of leaves plucking or at 3 years old
after planting. This tea plants have ever been fertilized with N,
unfortunately it was not recorded. The treatments were one rate of N
(using urea with 10 % 15N atom excess) and four rates of mulch. The
mulch consisted of pruning materials that varied from non up to 60
ton ha-1• The use of mulch was aimed to study its effect on the Ndff
distribution withing the tea plants.
The results of the expe~iment presented in Table 8 shows that
mulching with higher rate has clearly increased the Ndff· The Ndff
in leaf part compared to the Ndff in wooden part (stem and root) isabout 70% to 30%. This figure is expected to be a standard ratio for
tea plant as it was also found in apple tree (5).
In fact the increase of Ndff by mulching has a dual effects
i.e. (1) most of the Ndff was ditributed only in the leaf part and
(2) the Ndff in the leaf part was particulary distributed in youngerleaves or as yield.
Table 8. Effect of N application and mulching on the distribut
ion of Ndff in plants of the early stage of productivetea (6)
--------------------------------------------------------------------
Treatment
* -1Non p.m.* ) + 68.1 kg N h~l20 p.m.* ) + 68.1 kg N h~l
40 p.m. J + 68.1 kg N ha -160 p.m. ) + 68.1 ka N ha
266
Ndffwood
8.8
8.8
9.29.5
Ndffleaves
total
19.4
22.4
21.427.1
Ndffyoungleaves
total
5.1
7.3
8.29.9
28.2
31.230.6
36.6
Nitrogen Uptake by Tea Plants of 5 up to 60 Year old. The tea
plant which have very long productive age differ in its pattern on N
uptake from fertilizer as shown in Figure 1. The figure is showing a
pattern of Ndff, which occured in 5 classes of tea plants age during13 weeks after being applied with urea. The rate of urea, the method
of urea application, as well as the method of leaves plucking were
the same for all classes. The leaf plucking round wa done constantly
one in a week.
The trend of N uptake derived from fertilizer for 5 classes of
tea plants age were almost the same, i.e. an increement at the
second up to fifth week after fertilizer application and then tend
ing to decrease to the minimum from the sixth to the thirdteen week.
The total amount of Ndff in plucked leaves was also the same, except
for tea plants of 6 - 15 year old as seen in Table 9.
The yield of different plant ages during 13 weeks in fact was
different and tending to increase with increasing plant age percen
tage of Ndff at every leaf pIcking round, and it was much lowercompared to the plant ages of 1 - 5 years and 6 - 15 years. This is
the dilution effect in tea plants caused by plants productivity,
Table 9. The effect of tea plant ages on the dry matter yield, the
N~ff in the yeald, and the efficiency of ~ uptake from fertl Izer at fertilizer rate of 23 kg N ha- (7)
Classes of tea
plant age
1 - 5 year old
6 - 15 year old
16 - 30 year old
60 year old
Dry matter
(g)
119.498.9
224.5
248.9
Ndff in yieald(mg)
243.4
269.6
248.9
237.0
The efficiency
of N applied (%)
11.622.2
15.5
10.3
267
meaning that the higher the productivity, the larger the dilution
will occur.
For tbe older tea plants witb bieb Droduetivity, it ig D~@~Um-ably true that there is a high dependency of N need from natural N
in the soil. It means that tea levels of soil fertility or soil
organic matter in particular have to be maintained.
'Y.,I
A = 1-5 year old
, ,~ B = 6-15 year oldI \
f~ t\
C = 16-30 year oldI\ • l-
t+ .' \
D = 31-60 year oldI
\ ItE = > 60 year old. \
[/\+
\B It.--"-..,.'" \t
t, \
1\ +, 1'. I \ \,,. '. D.' ", C I \\ , .'. t.' ' v ·: I \ \I ..., •.... '. ( /'... •. ' , " .,,''''''............ '-' ." .'-- "
A \;. ,\ /,'{
.\I I, \
t\\\
, : .....
, ~1)
II11I)
Figur 1. The pattern of N uptake from fertilizer in plucked leaves
of 5 classes of tea plants age during 13 weeks
2G8
C()NCLUSIONS
1. In Indonesia tea soils which have slightly acid reaction and
rather high organic matter content, fertilization with urea has
not too much lost due to volatilization and leaching. Most of N
urea was lost as solution by run off when it applied by broad
casting or were still remained in the soil profiles.
2. Ndff for young unproductive tea plants was very much influenced
by the priming effect and the soil characteristics which enchance
the better growth of roots. The condition in which tea plant
roots are growing vigorously by the competition of N use in the
soils is won by plant againts soil microorganisms.
3. Ndff in tea plants of early productive stage has been distributedabout 70% in leaf part and about 30 % wooden part.
4. Times interval between two succession of the fertilizer gift
on productive tea plants using urea is better done at every 2,5
3 months.
5. Ndff tea plants of 6 - 15 year old has been characterized bystrongest uptake ans slightest dilution effect. A strong depen
dency of N source from natural N or from soil organic matter has
been observed in the tea plants with ages of older then 15 years.
ACKNOWLEDGEMENT
The author wishes to thank very much to all Soil Staffs of IAEA
Biotechnology Laboratory at Seibesdorf (Austria), especially Ms.
H. Axmann for their kindness on the correction of experimental
methodology and the 15N assay. Thanks very much are also aimed to
the Soil Staffs of CAIR-BATAN at Jakarta (Indonesia) for their
correction on the content of this paper. The auther thanks to Mr.
J. Buang Samudi and Mr. Topani for their cooperation and helps in
correcting and typing the text.
REFERENCES.
1. ANONIM, "Pemupukan urea dan Za pada tanaman teh produktif asal
biji", Laporan tahunan BPTK, Gambung (1975) 5.
269
2. BROESHART, H., "The efficient use of N in apple tree", IAEA Ex
perimental Report, Draft, Seibesdorf (1983) 8.
3. FENN, L.B., and D.E. KISSEL, Ammonia volatilization, from surface
applications of ammonia compounds on caleareous soils :1, Gene
ral theory. Soil Sci. Soc. Amer. Proc. 37 (1982) 855
4. FERESTONE, M.K., "Biologycal denitrification", Nitrogent in Agri
cultural Soils (STEVENSON, F.J., at al. ed.), ASA-CSSA-SSSA.
Agron. Mon. 22 (1982) 289.
5. WIBOWO, Z.D., "Erosi pupuk pada perkebunan teh di Jawa Barat",
Konggres Nasional HITI, Bogor (1985) 13.
6. WIBOWO, Z.D., "Pengaruh pemberian seresah pangkasan teh terhadap
efisiensi penyerapan N pupuk", Aplikasi Isotop dan Radiasidalam Bidang Pertanian dan Peternakan (Ris. Pertemuan Ilmiah
Jakarta, 1985), PAIR-BATAN, Jakarta (1985) 367.
7. WIBOWO, Z.D., Rumah tangga nitrogen tanaman teh muda, dengan
titik berat kejituan penyerapan nitrogen dari pupuk, TesisDoktor, Universitas Gajah Mada, Yogyakarta (1986).
8. WIBOWO, Z.D., and RACHMIATI, Y., "Efisiensi penyerapan N dari
pupuk pada berbagai umur tanaman teh" , Aplikasi Isotop danRadiasi dalam Bidang Pertanian dan Peternakan (Ris. Pertemuan
Ilmiah Jakarta, 1986). PAIR-BATAN, Jakarta, (1986) 7.
DISKUSI
RAHA)~ TEJASARWANA
1. Mohon penjelasan mengapa di tanah Regosol kehilangan pupuk mela
lui volatilisasi NH3 bisa keeil (8,8 kgiha) dibandingkan Latosol
atau Andosol, pada hal tentunyaimungkin KTK tanah Regosol keeil
sehingga kurang dapat menyerap NH4+ dari pupuk.
2. Teknologi pemberian pupuk di lahanikebun teh yang baik tampaknya
dengan Saprodik. Apakah aplikasi tekniknya lebih efisien diban
ding eara pemupukan biasaibroadcast ?
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ZUHDI SW.
1. Di sini Regosolnya adalah Regosol vulkanik
besardan pH-nya hanya ± 5, sehingga NTK-nya
Larutan ammonim pada pH <. 7 penguapannya
besar.
Efisiensinya dapat dihi tung dengan membandingkan dengan harga
pupuk yang hanyut oleh run off. Takaran pupuk Nihaitahun pada teh
250-350 kg N, apabi la yang hi lang 50 % harganya sangat mahal,
pada hal untuk membenam hanya diperlukan tambahan ± Rp. 25.000iha
2.
yang kadar debunya
tidak terlalu keeil.
menjadi (NH3) tidak
HARYANTO
Pada tanah podsol ik takaran pupuk N sangat berpengaruh terhadap
serapan N oleh tanaman, sedangkan pada tanah-tanah yang lain tidak.
Apakah mungkin hal ini disebabkan karena kandungan N awal (sebelum
perlakuan pemupukan) yang sudah tinggi pada ketiga tanah selain
tanah podsolik tersebut. Apakah Anda sudah melakukan analisis N
sebelum percobaan.
ZUHDI SW.
Kadar N pada tanah podsolik memang lebih rendah daripada tanah
tanah lainnya, ada dalam lampiran makalah lengkap. Tetapi sebenarnya
tidak sangat rendah, saya tuliskan. pula bahwa penyerapan N yang
lebih tinggi disebabkan oleh pertimbangan akar lebih baik daripada
di tanah-tanah lainnya (primin~ efect)
SOETJIPTO
1. Faktor-faktor apa saja yang menyebebkan kecepatan pupuk N diserap
tanaman teh ?
2. Berapa persen dari pupuk N yang diberikan itu diserap oleh
tanaman ?
3. Pemberian pupuk N berupa urea mungkin tidak akan memberikan
kwalitas daun pucuk tell sarna dengan bila pupuk N berasal dari ZA
atau lainnya. Mohon dapat diterangkan seperti halnya yang terjadi
pada daun tembakau.
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ZUHDI S.W.
1. Paling tidak oleh dua faktor utama yaitu: Kadar air yang optimal
JAh ~u1u lAha~ yand ltJal lerlalu renJab.
2. Tanaman muda hanya ± 30 %, sedangkan pada tanaman menghasilkan
mencapai 45 - 52 % .3. Belum diteliti lebih mendasar, tetapi diperkirakan ZA lebih baik
daripada urea.
ELSJE L. SISWORO
Apakah S yang ada pada ZA mempunyai pengaruh positif terhadap
tanaman teh, sehingga dapat dikatakan ZA mempunyai pengaruh lebih
baik dibandingkan urea.
ZUHDI S.W.
Pada saat ini sudah kelihatan bahwa pemupukan N perlu dicampur anta
ra urea dan ZA setelah produktivitasnya lebih darl 2500 kg teh/ha
dan lebih dari 10 tahun dipupuk urea saja.
DARSONO R.
Umur tanaman teh >30 tahun penyerapan pupuknya 15 % dan umur >60
tahun penyerapan 10 % • Berapa produksi teh (ton;'tahun) pada umur
30 dan 60 tahun ?
ZUHDI SW.
Produktivitas tanaman teh 30 tahun dan 60 tahun masih lebih bahkan
mencapai lebih dari 3 ton teh kering;'ha/tahun, namun variasinya
cukup besar tergantung pada populasi/ha dan keteraturan dari
kompsisi pupuk yang diberikan. Apabila tidak dipupuk N masih cukup,tanaman akan mengambil N dari tanah.
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