Wednesday, November 4, 2009
Convention Center, Exhibit Hall BC, Second Floor
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.