Correlation of Soil Properties with phosphate fixation in some alkaline-calcareous soils of Northwest India

Effects of soil properties on the rate of phosphate fixation and transformation of added phosphate into different inorganic P fractions were examined on 28 alkaline and calcareous soils of different agroclimatic zones of Haryana and Uttar Pradesh, India. Surface samples were treated with 200 μg P g‐1 soil and incubated at 25 ± 2°C and at 60% water holding capacity. Available P was determined at 7, 14, 28, and 56 days of incubation. The rate of decrease of available P was satisfactorily described by a second‐order kinetic rate equation. Clay, organic carbon, Al, Fe, and cation exchange capacity (CEC) was positively and pH was negatively related with rate constant. An 81.7% variation in rate constant was due to soil properties, while clay content alone contributed a 78% variation. CaCO3 affected the rate constant only in soils not varying in other properties. The variation due to soil properties in the transformation of added phosphate into different inorganic P fractions was: saloid‐P 77.7%, Al‐P 43.9%, Fe‐P 49.0%, Ca‐P 80.9%, and available P 79.9%, while the partial contribution of CEC to saloid‐P, pH to Al‐P, CaCO3 to Ca‐P, and clay to available P was maximum. The transformation of added phosphate into saloid‐P decreased logarithmically with increasing CEC, clay, active Fe, and organic carbon content. The transformation into Ca‐P increased and into Fe‐P decreased linearly with increasing pH and CaCO3 contents. The recovery of added P into available P was increased by 9.29% with a one unit increase in pH, while a 1% increase of clay decreased it by 0.62%. The contribution of inorganic P fractions to available P was 86.0% in these soils.