TROPSOILS
PUSLITTAN
WEST SUMATERA


TROPSOILS-Indonesia
Field Research Brief No. 3
April, 1984


TITLE: 1502. Phosphoros Rates and Methods of Application

RESEARCHERS: Mike Wade and Djoko Santoso

OBJECTIVES: 1. Determine optimum rates of P fertilizer on a
newly cleared soil (Paleudult),
2. Determine cost:benefit ratio of various methods
of applying TSP fertilizer,
3. Study the long term effects of various P
management (rates and methods) on crop
production and soil P levels,
4. Determine critical F soil test values for rice
and peanuts.

SOIL: Paleudult, LCeak; located in Sitiung Vc, forest cleared in
82/83 wet season, experiment initiated in December, 1983.

TREATMENTS: Randomized Complete Block with 3 replications, 4X6m
plots.


1. no P
2. 20 kg P broadcast
3. 40 kg "
4. 80 kg P
5. 20 kg P banded
6. 40 kg P'
7. 80 kg P "


8. 20 kg P in dibble hole
beside seed hole
9. 20 kg P in seed-hole
10. 20 kg P banded between
every other row
11. 80 kg P broadcast plus
2T lime, 50 kg K, 100 kg
MgS04 per hectare


Treatments 1-10 receive no base fertilizer, just P as
indicated. Lime, Ca(OH)2, is applied as a surface
broadcast at 325 kg/ha over the peanut rows after
planting as a Ca source.

The P treatments were applied at the rates indi-
cated on both of the first two crops, peanuts and mung
beans. Soil analysis indicated a build-up of P in all
but the zero plots. Therefore this third crop, rice,
was grown on the residual treatments, i.e. no new P
was applied.


CROP: This report covers the third crop in the experiment,
upland rice (cv. Arias, a selected, local variety). It was
planted in September, 1984 and harvested in February, 1985.
Spacing was 25 x 25cm, and 75 kg N (as urea)/ha was applied as
base fertilizer, 1/2 at 3 weeks and 1/2 at flowering.

RESULTS: Both grain yields and stover yields are shown
graphically in Figure 1 as affected by treatments, or actually










the residual of those treatments as no additional P was applied
to the rice. Grain yields were quite low. Although the variety
is a local one, supposedly tolerant to disease and pests, it was
in fact heavily attacked by sheath blight and stem borer.
Panicles were unusually small with a high percentage of empty
grains. Vegetative growth however was phenomenal, as indicated
by the very high dry matter yields. This is a more or less
predicted result for high fertility experiments when using local
varieties. Because this is a low-input experiment, with only
treatment 11 getting anything other than N fertilizer, a local
variety was thought-to-be the best choice but apparently was not.

There was a dramatic response to P (any rate or method of
application) compared to the control. However there were no
significant differences among any rate or method of application
for either grain or stover yield. Figure 3 shows basically a two
poi-nt-r-esponse curve, the zero and all the rest at plateau yield.
The residual of the first two applications, even at the lowest
rate (2 x 20 kg/ha), was sufficient P (+/-10 ppm by mod. Olsen)
for the rice.

Comparison of the three consecutive crops shows considerable
differences in their response to extractable soil P, with
peanuts > mung beans > rice. As the cycle is repeated in
subsequent seasons we can see if these extractable P vs yield
relationships hold over time.










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