Nitrogen release dynamics from organic and inorganic sources in a tropical Alfisol: Implications for synchronizing nutrient supply in rainfed sorghum systems

Abstract

Nitrogen release synchrony between soil amendments and crop requirements is essential for enhancing nitrogen use efficiency in rainfed agroecosystems. A laboratory incubation experiment was carried out for 112 days to determine the dynamics of nitrogen release from organic and inorganic sources in a tropical Alfisol. Farmyard manure (FYM), vermicompost (VC), poultry manure (PM) and urea were applied at the same rate of 30 mg N kg⁻¹ soil under controlled aerobic conditions. The changes in ammonium-N (NH₄⁺-N), nitrate-N (NO₃⁻-N) and total mineral nitrogen were determined periodically. Urea was found to mineralize at a faster and continuous rate, releasing nearly 95% of the applied N by the end of incubation. Poultry manure also continued to mineralize, releasing 67% of the applied N. In contrast, FYM and VC initially immobilized N up to 28 days, followed by gradual mineralization, releasing 33% and 29% of the applied N, respectively. Nitrate-N was found to dominate the mineral N pool throughout incubation. Although no crop was grown during incubation, the findings of this study would help to understand the patterns of nitrogen availability, which would be useful for synchronizing nutrient supply in rainfed sorghum systems. The study highlights the need for source-specific nitrogen management strategies to improve nitrogen use efficiency and sustainability in rainfed agriculture.