Assessment of phosphorus fixing capacity in different soil orders of India

An experiment was conducted to assess the phosphorus fixation capacity in five soils orders with contrasting characteristics at different concentration of added phosphorus. The surface soil (0-15cm) samples were collected from five soil orders namely Alfisols, Inceptisols, Vertisols, Aridisols and Entisols of different locations of India. The collected soil samples were analyzed for physico-chemical properties and phosphorus fixing capacity. The initial soils samples were acidic (5.77) to alkaline (8.53) in reaction, high organic carbon content and low to medium available phosphorus with presence of 663 ppm to 1669 ppm active iron. The maximum phosphorus fixation (%) was observed in Alfisols (88.68) followed by Inceptisols (68.73), Entisols (68.33), Vertisols (66.84) and Aridisols (58.24). About 58-89% of added phosphorus was fixed in the soils and the maximum fixation was in the Alfisols while the least fixation was observed in Aridisols. Alfisols soil showing higher phosphorus fixing capacity might be due to presence of sesquioxide (active iron and aluminum oxides) that complex with phosphate ions. Phosphorus fixation capacity was negative and significant correlated (r = - 0.76*) with soil pH and positively correlated with active iron (r = 0.84*). Multiple regression analysis revealed that 85 percent of phosphorus fixing capacity of soil depends on soil pH, organic carbon, clay and active iron. Under such condition, it must be overcome by application of phosphorus on the basis of cropping sequence instead of individual crop needs to be taken into consideration and use of otherphosphorus sources such as Phosphorus bio-fertilizers, organic manures, and low grade rock phosphates for improving phosphorus use efficiency.