SOIL TEST-CROP RESPONSE CORRELATION STUDIES ON THE RICE CROP GROWN IN THE VERTISOLS UNDER SRIRAM SAGAR PROJECT AREA
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Date
1991
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ANDHRA PRADESH AGRICULTURAL UNIVERSITY HYDERABAD
Abstract
A field study on the soil test-crop response
correlation was carried out in Rabi 1989 with paddy
(var. Pothana) as the test-crop on the black clay l~fm
soil (pH 8.1, OC¼ 0.81, -!vailable N 170 kg ha ,
ailable p~~sphorus 10 kg ha and availabl7 potassium
890 kg ha ) at Agricultural Research station, Warangal
representing the paddy soils of Sriram Sagar Project
area in Warangal district to calibrate soil test values
for Rabi paddy, to develop fertilizer recommendation
doses for obtaining maximum yield, maximum profit and
desired target yield and to testify the genuineness/
validity in terms of response, advantag·e of the
conjoint use of organic manure (FYM) with inorganic
fertilizers .
Four fertility gradient strips (0 X, 1/2 X,
1 x and 2 X) were created with respect to phosphorus·
and each strip was divided into 30 sub plots which
received ~~mbinations of three levels of N (80, 160 and
24Q 1kg ha ), three levels of P2o5 (40, 80 an~1120 kg
ha ) and 3 levels of FYM (0, 20 and 40 kg ha equivalent
N) with 3 controls as treatments. Initial soil
samples collected from each sub plot were analysed for
nitrogen (OC%-N and KMno4-N), phosphorus (Olsen's-P)
and potassium (Ammonium acetate-K) contents .
Treatment-wise grain and straw yields were recorded and
the plant samples collected were analysed for N, P and
K contents and their uptake was computed. Relationship
between yield and soil test values as well as fertilizer
doses were developed through multiple
regression analysis.
Both methods of N estimation viz., OC%-N and
KMnO
4
-N ·.·:ere found to be equally good to predict the
yield and nutrient uptake. The grain and straw yields
of contro~ (untreated) plots in~1eased from lower
fertility strip (i.e., 3812 kg h~
1
in OX) to higher
fertility strip (i.e., 4621 kg ha in 2 X).
1;0 response to FYM application was noticed in
terms of grain and straw yielos and thus there was no
advantage in using the organic manure conjointly with
chemical fertilizers.
T~e following fertilizer adjustment equations
based on different approaches were developed for
nitrogen and phosphorus by following regression techniques
to derive the optimum doses for obtaining maximum
yield and =aximum profit per hectare for any given soil
test vali;.es.
Fertilizer adjustment equations for maximum yield
~I= 266-37 SN (OC%-N)
FP2 o5 = 251-7.18 SP (Olsen's-P)
Fertilizer adjustment equations for maximum profit
r!i = 266-37 SN -19. 53 R ( OC%-N)
FP2o5 = 251-7.18 SP -14.79 R (Olsen's-P)
(Where F.. is the ratio of cost of a unit of fertilizer
and price of a unit of grain yield, SN= soil N as
estimated by o.c. per cent method and SP= soil phosphorus
as indexed by Olsen's-P method)
Tr:e results indicated that by following fertilizer
recommendations based on soil analysis it was
possible ~o get the maximum and economic yield with
much lower levels of fertilizer application than those
obtained ~,.-i th blanket recommended doses.
Eased on nutrient requirement, soil and fertilizer
con~ributions of nitrogen and phosphorus, the
following nitrogen and phosphorus fertilizer adjustment
equations for desired yield targets were derived.
~I= 6.66 T -363.69 SN (OC%-N)
FP
2
05 = 3.89 T -7.33 SP (Olsen's-P)
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