Abstract
Total hydrolysable organic N in unfertilized soil gradually decreased with increase in the period of incubation. The decrease was more marked under waterlogged conditions, suggesting a higher rate of mineralization of native organic N. A distinct decrease in the amount of hydrolysable NH4+ N and amino acid-N was observed under all the moisture regimes in the urea-treated soil. However, in a system treated with diammonium phosphate (DAP), the same trend was found under 30% of moisture-holding capacity (MHC) and waterlogged conditions. N-serve addition caused a decrease in the amount of total hydrolysable organic N during the early stage of incubation in the unfertilized soil, with maximum decrease under 60% of MHC and minimum under waterlogged conditions. As with the unfertilized system, the addition of N-serve promoted mineralization in both the urea- and DAP-treated soil at all three moisture regimes at an early period of incubation, and the rate of mineralization decreased with increase in the incubating soil moisture levels.
