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Birsa Agricultural University, Ranchi

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19951
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Subject: Seed Science and Production Technology × End date: 1997 × Start date: 1993 × Type: Thesis × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Transformation and availability of Phosphorus in Acid Soils with Special Reference to high Analysis Phosphatic Fertilizes
    (Birsa Agricultural University, Ranchi, 1995) Gutam Kumar Ghosh; Dr. A. K. Sarker
    Laboratory investigations were conducted to study (1) the P availability indices in relation to soil properties, (ii) the extent of P fixation in soils, (111) the rate and extent of hydrolysis of Triammonium pyrophosphate in soils, and (iv) P sorption behavior in soils. Field/pot experiments were designed to evaluate (i) the relative efficacy of Ammonium polyphosphate (APP) vis-a-vis other phosphatic carries on upland rice (Oryza sativa L.) (ii) the relative efficiency of soil fertilizer P reaction products vis-a-vis ortho- and polyphosphate to gram (Cicer arietinum L.). Results indicate: wide variations in the indices of P availability in soils belonging to two major soil series of Chotanagpur and Santhal Parganas region. Correlation, multiple regression and path coefficient analysis between P availability indices and soil properties reveal that organic carbon was significantly correlated to Bray P₁ (r=0.535**) and Olsen P (r=0.445**) whereas total P was significantly correlated with Bray P₁ (r=0.465**). Clay content was negatively correlated with total P (r=-0.462**) and phosphate potential towards the variations in Bray P₁ (28.96%) and Olsen P(19.56%). Fixation of added P ranged from 46 to 79% in acid soils of Bihar. Clay, soil reaction, CEC and organic matter influenced this parameter. Pyrophosphates undergo hydrolysis in soil leading to the formation of orthophosphates, which are plant available. Rate of hydrolysis of pyrophosphate, applied as (NH4) HP₂07.H₂0 was measured in soils. Hydrolysis was faster under flooded conditions than that at field capacity. The half-life values of pyrophosphate hydrolysis were 6.8 and 1.8 days in Putida soil (pH 7.4) and 10.5 and 2.7 days in Ranchi soil (pH 5.5) under field capacity and flooded moisture content, respectively. The equilibrium phosphate sorption and desorption behavior and the kinetics of adsorption were studied in soils. Phosphate sorption data at 25°C were fitted to the Freundlich, Langmuir and Tempkin adsorption isotherms. Freundlich equation showed a better fit of the equilibrium data than the Langmur equation. The soils varied widely in their capacity to desorb and retain P. The P retention (adsorption) capacity of the soils were follows: Lo (0% NPK) > L₁ (50% NPK) > Ranchi upland > Ranchi lowland> L₂ (100% NPK) > L (150% NPK). AS The P desorption capacity of the soils were in the following order : L3 (150% NPK) > L₂ (100% NPK) > L₁ (50% NPK) > Ranchi lowland > Ranchi upland > Lo (0% NPR). The adsorption - desorption parameters viz. Freundlich K, Langmuir adsorption maximum, binding energy constants and P sorption at 6.45 u mol P/L in solution ranged from 76 to 257 mg P/Kg, 564 to 778, 0.784 to 3.063 L/mol P and 27 to 105 mg P/Kg, respectively in the soils. During desorption, the amount of sorbed P at A given equilibrium P concentration was always higher than that during desorption. indicated the low desorbability of the sorbed P. The P sorption - desorption parameters viz. Freundlich K, Langmuir adsorption maxima. Binding energy were closly correlated with exchangeable Fe and Al content of the soils whereas negatively correlated with organic carbon, CEC, exchangeable Ca and Mg and lime potential. The free energy for P sorption (-AG*) in soils ranged from values indicates the spontaneity of the sorption process in these acid soils. Field experiments conducted on upland rice (Oryza sativa L.) "Brown Gora" during wet season of 1992 and 1993 indicate a positive response of upland rice to different P sources. The crop recovery varied widely (9.97 to 42.44 per cent) with sources of P application in soil. The apparent recovery of fertilizer P was more at lower levels of added P than that at higher levels. APP applied 830 kg P₂05/ha resulted in the highest recovery and crop response (26.9 and 30.0 kg grain/kg P₂05) during 1992 and 1993, respectively). Pot culture experiment conducted to evaluate the relative efficiency of reaction products (Struvite, Brushite, Variscite and Strengite), orthophosphates (DAP and SSP) and polyphosphate (APP) as sources of P for gram (Cicer arietinum L.) in a typical acid soil reveal struvite to be superior or equally effective as APP, DAP or SSP as source of P for gram. Uptake of P also varied significantly with different P sources and levels of P application. Strengite. was least effective in enhancing the yield and P uptake by the crop.