MSc

A pot culture experiment on the "Influence of phosphorus on absorption
and dynamics of nutrients in rice" was conducted during December 2002 to April
2003 at the Radiotracer Laboratory, College of Horticulture, Kerala Agricultural
University, Vellanikkara.
The distribution pattern, content-effectiveness relations of phosphorus on
rice productivity in relation to soil types, nutritional levels and the role of organics
were investigated in the present study
Plant height, tiller number, productive tillers,filled spikelets per
panicle,grain and straw yield showed significant increase in kole soil treated with
90:45:45 kgha' NPK along with Pongamia leaves @ 5 tha' (TII).
Chlorophyll 'a' and total chlorophyll were highest in Tll having kole soil
treated with 90:45:45 kgha' NPK along with Pongamia leaves @5 tha-I at panicle
initiation and at 50 per cent flowering. A favourable cell sap pH was also noticed
inTll_
TII gave highest plant content of N in both laterite and kole soil. P and K
contents were also more in treatments having inorganics with Pongamia. Iron
content of rice plants decreased with advancement in the stages of growth.
Percent phosphorus derive~ from fertilizer (%Pdff) had highest value at
maximum tillering and thereafter it decreased. %Pdff was increased with
increasing levels of Phosphor~ls application. When the applications of inorganics
with and without organics are compared in laterite and kole soil, application of
single super phosphate with organics always gave highest %Pdff than with single
super phosphate alone. Laterite soil treated with 90: 67.5: 135 kgha' NPK along
with Pongamia leaves @ 5 tha' (Tg) obtained 10.68 % Pdff and the- same
treatment in kole soil had 12.96% of %Pdff at harvest.

%Pdfs was low at maximum tillering and thereafter increased up to harvest.
At maximum tillering, laterite soil treated with 90:45:45 kgha' NPK without
organics (T1) gave highest %Pdfs of 93.45% and the kole soil treated with
90:22.5:90 kgha' NPK without organics (T13) gave highest %Pdfs of 93.51 % ,At
50% flowering and at harvest in both soils treated with 90:22.5:90 kgha' ofNPK
with or witnout organics recorded highest %Pdfs. Per cent uptake of applied P
fertilizer by the plant also had an increasing trend from maximum tillering to
harvest. But it was decreasing with respect to increase in levels of phosphorus
from 22.5 kghalto 67,5 kgha'.
Laterite soil treated with 90:67,5:135 kgha' of NPK along with
Pongamia leaves @ 5 tha-I (Ts) registered highest concentration of available P of
16,8 rngkg' followed by the same treatment in kole soil with 16.7 mgkg".
A vailable iron content of soil after harvest was more in treatments having
Pongamia in laterite soil while it was more with rice straw applied treatments in
kole soil
The present study indicate that organics-Pongamia and rice straw in
conjunction with inorganics enable consistent supply of phosphorus for achieving
enhanced grain and straw yield in both late rite and kole soil.Though Pongamia
along with inorganics is an ideal fertilizer schedule for rice crop in terms of yield.
when the cost of incorporation of Pongamia is considered, rice straw along with
inorganics is more profitable and convenient.