TROPSOILS RESEARCH BRIEF 1985:


Title: Response of Upland Rice and Soil K Levels to K
Fertilization and Green Manure Applications at Sitiung 5

Experiment #: 3501

Researchers: Dan Gill, Antonius Kasno and J. Sri Adiningsih

Objectives: 1. To examine the effects of K rates and green
manure applications on rice yields and soil
exchangeable K levels.
2 To compare the effects of 80 kg K/ha applied in
a single dose and in a split application.
3. To observe the effect of green manuring on Ea,
Mg and K movement and retention within one
profile of an ultisol in the Sitiung area.

Soil: Udult, probably an orthoxic tropudult cleared by bulldozers
3 ears ago, but never cropped. FCC: Ceak.

Treatments: Treatment design was an incomplete factorial set out
in a randomized complete block design with 3 blocks.
Seven rates of K were used: 0, 10, 20, 40, 80, 120
and 240 kg K/ha. Green manure applications of 10 t/
ha of Calopogonium (fresh weight) were made to 2
separate plots with 0 and 80 kg K/ha applied. The
final'treatment was a split application of 2 x 40 kg
K/ha at planting and at 57 days after planting.

Crop History: Cultivar "Sitiung" (GH 324) was planted on 12 Nov.
1984 with a blanket application of the following
fertilizers (kg/ha): 65 urea applied once, 500 TSP,
125 kieserite, 5000 lime and 10 each of Mn, Zn and
Cu sulfate. Carbofuran was applied at planting and
diazinon and sevin were applied several times for
insect control. Benomyl 50 W (Benlate) was sprayed
once in an attempt to slow the development of
blast. Harvest--occurred on 28 Feb. 1985, 108 days
after planting.

Results: The -crop-grew- well initially, with a large response
being observed visually to both K and green manure. Shortly
after tiller initiation-r-leaf- blast symptoms became visible and a
blast rating performed at this time showed K to be very effective
in assisting the plants' 'resistance mechanisms) (Table 1). How-
ever, the disease became progressively worse, with other symptoms
perhapss Helminthosporium) also appearing. In the end, neck
blast- and perhaps several other diseases caused complete panicle
sterility- and harvest was only possible for the straw. Straw
weight showed a significant response to K, with maximum yields
occurring around 120 kg K/ha (Figure 1). Data at lower levels of
K application showed a greater degree of scatter and it is hoped
that this variability will be accounted for by soil analysis data












which is not yet available. Calopogonium green manure was also
very effective at decreasing blast incidence and increasing straw
yields (Table 2), pernaps in large part because the 10 t/ha
applied contained 60.1 kg K/ha. Split applying 80 kg K/ha was
rot more effective in producing straw yields than a single
application (Table 3); in this experiment, it gave a significant
decrease in yield, perhaps due to the fact that the second
application occurred about the time the disease attack was
becoming most severe. The experiment is continuing with a
soybean crop, while measurements of soil physical as well as
chemical parameters are being undertaken to better understand the
effect of the green manure.


Table 1.


The effect of K rates on blast rating and straw yields
of upland rice at Sitiung 5.


Potassium Rate
(ko/ha)


Blast Rating
(1-10)


Straw Yields
(t/ha)


1 C)
20
40
s0
120
240


20-split


Tab e: 2.


-The effect of green-manure applications on blast rating
and straw yield at 2 K levels in Sitiung 5.


BLAST RATING (1-10)
K rate (kg/ha)
0 80 Mean


STRAW WEIGHTS (t/ha)
K rate (kg/ha)
0 80 Mean


Green 0
Manure
(t/ha) 10


6- 2

2 1


. 27 3.56


1.5


2.92


4.57 6.59 5.58


1.17
3.83
3.31
3.43
5.84
7.52
6.68

3.56







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