Effects of Temperature and Soil Type On Ammonia Volatilization From Slow-Release Nitrogen Fertilizers.

Ammonia volatilization is the major pathway for mineral nitrogen loss from N sources applied to soils. The information on ammonia volatilization from slow-release nitrogen fertilizers is limited. This study evaluated NH₃ losses from four slow-release nitrogen fertilizers with different proportion of urea and urea polymer (L30, G30, N42; and NF) applied to two types of soils during 78d incubation in the laboratory. The potential cumulative NH₃ volatilization loss in the sand soil increased by 1.35, 1.70, and 1.75-fold from 20 to 30 °C  for N42, L30 and G30 respectively. Increasing the proportion of urea in the slow-release fertilizer increased NH₃ volatilization loss. In the sand soil at 30⁰C, N42 lost NH₃ which occupied 46% of applied N, followed by L30 at 44%, G30 at 22% and NF at < 1% during 78d. There was a positive correlation between NH₃ volatilization rate and accumulated NH₄-N  released from the fertilizers (r = 0.269, p = 0.12 for N42; r = 0.468, p < 0.01 for L30 and r =0.392, p < 0.05 for G30). When the four fertilizers were incubated in the loam soil, the potential cumulative NH₃ volatilization loss to the amount of applied N was only 9.2%, 3.1 % and 1.7% for N42, L30 and G30 respectively. The loam soil had high nitrification activity which decreased the availability of NH₄ in soil for NH₃ volatilization over the period of 78d. These results indicate the composition of slow-release fertilizer, soil temperature and soil type are main factors to dominate ammonia volatilization from slow- release fertilizers.