Ammonia Volatilization From Nitrogen Fertilization In Winter Wheat-Summer Maize Rotation System In The North China Plain

Ammonia volatilization is an important pathway of N losses in the winter wheat-summer maize rotation system in the North China Plain. However, the quantified information about ammonia volatilization under different conditions in this system is limited due to lack of available measurement method. In this study, a wind tunnel system was established and used to measure ammonia volatilization from the conventional and optimized N inanagement systems of winter wheat-summer maize rotation in the North China Plain, and the effect of different nitrogen fertilizer types and application methods on ammonia volatilization was also studied by using this wind tunnel system. The main results were as follows:(1) An average ammonia recovery of 95.7% for the wind tunnel systems was found in a recovery experiment. The wind speed in wind tunnel is very close to that of outside.(2) Measurement results indicated that application time and application method of N fertilizer considerably influenced ammonia volatilization. Surface application favored ammonia volatilization. The cumulative volatilization losses from ammonium bicarbonate amounted to11.3% by deep placement but 27.9% by broadcasting. 19.7% of total applied nitrogen as urea was lost by irrigation immediately, but 34.0% by 5 hours later irrigation.(3) The cumulative volatilization loss during wheat wheat growth season amounted to 58.3 kg N hm-2 by conventional N fertilization treatment (N rate: 300 N kg-hm-2), but only 15.0N kg.hm-2 by optimized N fertilization treatment (N rate: 34 N kg.hm-2).(4) The cumulative volatilization loss during summer maize growth season amounted to 77.5 N kg-hm-2 by conventional N fertilization treatment (300 N kg.hm-2) and 24.8 N kg-hm-2 by optimized N fertilization treatment(83.7 N kg-hm-2).(5) Nitrogen fertilizer type considerably influenced ammonia volatilization. At the same N rate and some application method, the percentage ammonia loss from calcium ammonium nitrate was15.3% , while 18.9% from urea. The percentage ammonia loss from ammonium nitrate was 2.7%, while 24.0% from urea under the same condition. And the percentage ammonia loss was 12.5% from ammonium sulphate nitrate, while 28.0% from urea the same condition. DMPP had no effect on ammonia volatilization from urea and ASN.