SOIL TEST CALIBRATION STUDIES FOR A PADDY - PADDY CROPPING SEQUENCE IN VERTISOLS OF WARANGAL DISTRICT
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Date
1993
Authors
Journal Title
Journal ISSN
Volume Title
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ANDHRA PRADESH AGRICULTURAL UNIVERSITY HYDERABAD
Abstract
Two field experiments were conducted with paddy
(variety Surekha) at Warangal Agricultural Research Station,
Kharif 1988 and Rabi 1988-89 on black clay loam soi l s, to
calibrate soil test methods for Kharif and Rabi paddy and to '
develop fertilizer recommendations for obtaining maximum
yield, maximum profit and desired target yields.
Four fertility gradient strips (Ox, l/2x, lx and 2x)
were created witt respect to N, P and Kand each strip was
devided 27 treatments and 3 controls. Treatments we~e
alloted in such a manner that the plot which received a
maximum dose of fertilizer with respect to a particular
nutrient in Kharif would receive the l owest dose in Rabi and
vice-versa. Soil and plant samples were analysed for N, P
and K aand their uptake was computed in both the exper1meRts.
KMn04-N method in Kharif and both oc~-N aD-d KMno 4-N
methods of N estimation in Rabi were found to predict ehe
yield and nutrient uptake. Olsen's method for available P
and NH40AC method for available K were proved suitable
indices in both Kharif and Rabi. A positive and linear
relationship was observed between grain yield and uptake of
N, P and K of paddy in Kharif and Rabi.
Yield respon~I to applied N (upto 240 kg ha-1 ) and
P2o5 . (upto 120 kg ha ) was found significant in both the
experiments.
The following fertilizer adjustment equations based
on regression analysis were developed for N, P and K to
derive optimum dose for obtaining maximum yield and maximum
profit per hectare for any given soil test values :
For Kharif 1988 :
FN ::::; 157 0 . 21 SN (KMn04-N) Maximum
yield
FP2o 5 = 141 1 . 78 SP (Olsen's- P)
FK 0 2
::::; 65 - 0.01 SK (Amm. Ace. K)
FN = 157 0 . 21 SN (KMn04-N) - 16.67 R Maximum
profit
= 141 ~ 1.78 SP (Olsen ' s-P) - 25 . 00 R
= 65 - 0.01 SK (Amm. Ace . K) - 16.67 R
For Rabi 1988-89
FN
FN = 147 - 0.15 SN (KMno4-N)
FP2o 5 = 159 3 . 21 SP (Olsen ' s-P)
FK2o = 64 - 0.01 SK (Amm. Ace . K}
= 147 - 0 .15 SN (KMno4-N) 16.67 R
= 159 3.21 SP (Olsen's-P) - 14 . 48 R
= 64 - 0.01 SK (Amm. Ace . K) - 15.38 R
Maximum
yield
Maximum
profit
(Where R is ratio of cost of a unit of fertilizer nutrient
per price of a unit of grain yield.)
Based on nutrient requirement,
contributions of N, P and K, the
adjustment equations for desired yield
for N, P and I< .
For Kharif 1988 :
FN = 5.75 T - 0.75 SN
FP2o5 = 2 . 75 T - 3.94 SP
FK20 = 1 . 99 T - 0 .12 SK
soil and fertilizer
following fertilizer
tar~ets wa~e derived
For Rabi 1988-89 :
FN = 3.97 T 0.54 SN
FP2o5 = 2 . 65 T - 3 . 52 SP
FK
2
0 == 1 . 51 T - 0.08 SK
Prediction equations to calculate post harvest soil
test values after Kharif were developed as given below .
1 . SN(pH) = 0.3706 + 0.016 * SN{I) 0.009 ** FN + 0 . 0001 **G Y
(OC)
2. SN(pH) = 280 + 0 . 0132 * SN(I) - 0.2158 **F N - 0 . 0193 **G Y
(Irnno
4
-N)
3. SP(pH) = 14 . 7491 + 0 . 1871 ** SP(I) - 0 . -0022 ** FP + 0.0013GY
(Olsen's-P)
4. SK(pH) = 80.4414 + 0.6993 **S K(I) + 0.1075 * FK + 0 . 0230 **G Y
(Amrn . Ace . K)
Using these equations fertilizer can be calculated
without soil analysis for targetted yields of Rab~ paddy .
The studies have developed as basis to recommended
fertilizer doses for targetted yields of Kharif Paddy - Rabi
paddy cropping sequence using a one time soil analysis at the
begining of Kharif season.
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