Effect of integrated use of inorganic fertilizers and organic materials on the distribution of different forms of nitrogen and phosphorus in soil

A study was undertaken to evaluate the effect of chemical fertilizers and organic manures (FYM, press mud, burnt rice husk and green manure) on the amount and distribution of nitrogen (N) and phosphorus (P) fractions in soil after two cycles of rice-wheat cropping system. Application of chemical fertilizers alone or their combined use with organic manures significantly increased all the forms of nitrogen except unidentified hydrolysable-N over control or their initial status. Among the various N fractions, amino acid-N was the dominant N fraction. On an average, amino acid, amino sugar, ammonia-N and unidentified hydrolysable-N constituted about 33.2, 8.9, 29.0 and 29.8% of the total hydrolysable-N, respectively. The amount of P recovered in saloid-P, Al-P and Ca-P form increased significantly with the application of inorganic fertilizers and their combined use with organic materials over control. The highest amount of all the forms of P was recorded under farmyard manure followed by green manuring and press mud treatments. Averaged across treatments, saloid-P constituted about 2% of the total P. The Al-P and Fe-P accounted for 8.4 and 12.1% of total P, respectively. The Ca-P accounted for nearly 44% of total P.