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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