Dry and wet nitrogen deposition in agricultural soils in the Loess area

With rapid rise of human activities induced active atmospheric nitrogen,the atmospheric nitrogen deposition has increased significantly,and consequently response of the ecosystems has gradually become obvious.The study of the impact of nitrogen deposition on agricultural ecosystems can supply the basic support for the N cycling and budget calculation and guide farmers applying N fertilizer scientifically and reasonably.Furthermore,it is expected that the study will provide basal support for in-depth research on the environmental effect and bio-availability of nitrogen deposition.Atmospheric precipitation and N deposition were collected in a one-year period(from 2006 to 2007)in Yangling and Luochuan County in Shaanxi Province respectively using APS-2A model automatic sampling equipment.Total nitrogen,monthly variation and the proportion of various types of nitrogen were monitored and analyzed.The results showed that the rainfall in Yangling in 2006 was 507.8 mm and the total nitrogen was 20.6 kg/(hm2·a)in which wet deposition account for 93% with the amount of 19.1 kg/(hm2·a).The remaining parts of the total nitrogen came from the dry deposition with the amount of 1.5 kg/(hm2·a).Nitrate rate was 7.3 kg/(hm2·a),accounting for 36% of total nitrogen.The rainfall in Luochuan from June 2006 to May 2007 was 579.5 mm and the total nitrogen deposition flux was 12.7 kg /(hm2·a).Wet deposition of N reached at 11.4 kg /(hm2·a)which accounted for 90% of total nitrogen.On the contrast,the dry deposition was 1.2 kg /(hm2·a),accounting for 10%.69% of total N deposition fluxes was nitrate with the amount of 8.68 kg /(hm2·a).The differences of N deposition flux and nitrogen forms largely reflect the N resource was come from the agricultural production by the human activity in the regions of Yangling and Luochuan.