黄土区降水降尘输入农田土壤中的氮素评估

随着人类活动引起大气活性氮的急剧增加,大气氮沉降亦明显增加,由此引发的各生态系统的响应也逐渐表现出来.研究黄土区氮沉降,对农业生态系统的氮素循环与平衡提供一定的数据支持,同时为农民科学合理施肥提供依据,为研究氮沉降的环境生态效应和生物有效性提供科学支撑.用APS-2A型降水降尘自动采样器对陕西杨凌和洛川地区2006～2007年的降水降尘输入氮总量、月动态变化及各形态N的贡献率进行了监测与分析.结果显示杨凌点2006年总降雨量为507.8 mm,总N沉降通量为20.6 kg/(hm2·a),其中N湿沉降通量为19.1 kg/(hm2·a),占93%;降尘输入的N通量为1.5 kg/(hm2·a),占7%.总N沉降通量中NO-3-N为7.3 kg/(hm2·a),占36%.洛川点2006年6月～2007年5月总降雨量为579.5 mm,总N沉降通量为12.7 kg/(hm2·a),其中N湿沉降通量为11.4 kg/(hm2·a),占90%;降尘输入N的通量为1.2 kg/(hm2·a),占10% .总N沉降通量中NO-3-N为8.7kg/(hm2·a),占69%.两个点N沉降通量和氮素形态的差异在很大程度上反映了活性N主要来自人为活动,即农业生产排放的活性N.

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.