CARBON AND PHOSPHORUS DYNAMICS IN SOIL IN RELATION TO NUTRIENT MANAGEMENT IN RICE-WHEAT SYSTEM
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Date
2012
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PAU Ludhiana
Abstract
The study comprised of two field and two laboratory experiments. In field experiment on
organic and integrated nutrient management of basmati-wheat sequence, the effect of inorganic, organic
and integrated nutrient management was studied on crop yield and soil properties. Water infiltration rate
was highest and soil bulk density was lowest in recommended fertilizer + FYM (INM2) treatement. Total
water stable aggregates (WSA) in the 0-15 cm soil depth ranged from 58.5 to 82.4 per cent; minimum
WSA were observed in control and maximum in INM2 treatment. Among the aggregates 0.11-0.25 mm
fraction constituted the greatest proportion and > 2 mm fraction constituted the least proportion.
Maximum pH and EC were recorded in control plots and minimum in plots receiving 400 kg N ha-1
through FYM. Soil organic carbon (SOC), aggregate associated C, labile C and hot water soluble C was
highest in FYM 400N treatment. Ammonical-N, nitrate-N, Olsen P, Bray I P, ammonium acetate
extractable K, soil P fractions and total P in soil were highest in INM2 treatment and lowest in control.
Grain yield, straw yield, NPK content and their uptake by basmati and wheat were maximum in INM2
treatment and minimum in control. Basmati and wheat grain yield were significantly correlated with soil
P fractions and the highest correlation was observed with saloid-P. In the second experiment, effect of
rock phosphate on crop yield and P fractions in soil under rice-wheat sequence was studied. Highest SOC,
Olsen P, soil P fractions, ammonium extractable K and non-exchangeable K were recorded in rock
phosphate (RP) and FYM treatment and lowest content of all these parameters was observed in control.
Highest pH was observed in control P treatment and lowest in treatment where FYM was applied along
with RP. Grain yield, straw yield, NPK content and uptake in grain and straw were also highest in plots
recieving P from RP along with FYM. Grain and straw yield of both the crops were significantly
correlated with all the soil P fractions (Sa-P, Al-P, Fe-P and Ca-P). Highest correlation of paddy grain
yield was observed with Sa-P whereas wheat grain yield gave highest correlation with Al-P fraction and
lowest with Ca-P. Rock phosphate gave almost similar crop yield and P availability in soil as that with
SSP. In laboratory study I, P was extracted by different methods and the lowest amount of P was
extracted with AB-DTPA and the highest with Bray-I method. Phosphorus extracted by Olsen, Bray-I,
Morgan and AB-DTPA methods gave significant positive correlations with grain yield and nutrient
uptake of paddy and wheat. In the soils from long-term experiments with different fertilization history,
maximum P adsorption was observed in unammended soil and minimum in soils where FYM was applied
alongwith chemical fertilizer. Contrarily, desorption was minimum in control plots and maximum in plots
where organic sources along with inorganic fertilizers were applied. Adsorption data fitted well to both
Freunlich and Lagmuir models.
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