Comparison of different extractants for evaluating nitrogen mineralization from diverse organic manures and their effect on soil properties

Addition of organic manures to soil is an important management strategy to improve organic matter status and nutrient availability, and to provide better soil conditions. A laboratory incubation study was undertaken to compare the different extractants for evaluating nine organic manures varying in chemical composition for predicting nitrogen mineralization and their effect on the changes in biochemical parameters over a 28-day period in a sandy loam soil. Among different extractants, 2M KCl was found the most suitable for mineral N (NO₃⁻-N + NH₄-N) extraction. The release of NH₄⁺-N at 7^th days after incubation was highest with goat manure (37.4 mg NH₄⁺-N kg⁻¹ soil) and lowest with pig manure (8.25 mg NH₄⁺-N kg⁻¹ soil). With time, the NO₃⁻-N mineralization increased progressively and peaked at 2 weeks after incubation, and then showed a decreasing trend. Changes in soil chemical and biochemical parameters (pH, EC, available-P, available-K, dehydrogenase and alkaline phosphatase) were observed due to incorporation of different organic manures during first few days of incubation compared with control. Among biological parameters, highest dehydrogenase and alkaline phosphatase activities were shown by non-broiler manure followed by pig manure. The present study concluded that organic manures varying in nutrient composition may be useful for quantifying the return of organic matter and nutrients in soil.