黄土丘陵区土壤—作物系统氮素特征与管理

Nitrogen characteristics and its management of soil-crop systems in loess hill area

基于长期定位试验,对黄土丘陵区的晋西北河曲县砖窑沟试验区土壤氮素资源与分布,土壤氮素变化和农田氮素平衡进行了分析,并探讨了该区氮素管理策略和施肥方案.结果表明,试验区土壤全氮含量平均为0.4 g/kg,土壤碱解氮为16.76 mg/kg,氮素水平低,供氮能力差.土壤氮素含量呈现耕地>草地>林地的分布态势.经过连续13年的施肥处理,施有机肥和有机、无机肥配施0-20cm土层全氮含量显著提高了12.0% ～ 105.6%,20-40cm土层全氮含量变化没有显著差异;各施肥处理0-20cm土壤碱解氮均呈上升趋势,增加了32% ～ 299%,土壤有效氮的增加与连续施入有机肥的量有关.施肥处理的糜子农田的土壤氮素均呈现出盈余状况,马铃薯田则基本保持平衡.因此,在轮作周期中应根据前茬作物的需氮特性和收成情况确定当季作物的氮肥施用量.糜子和马铃薯的施肥应以氮肥和有机肥为主,氮磷比例分别为1∶0.5 ～ 0.7和1∶0.7左右为宜.

A long-term experiment was carried out on a typical loess soil in Hequ county, northeastern Shanxi province, to study the soil N fertility. Results showed that soil nitrogen content in the experiment area are much lower than those in other similar areas and the nitrogen supplying potential of soils is low （total N 0.4 g/kg averaged and alkali-hydrolyzable N 16.76 mg/kg averaged）, The amounts of soil nitrogen content in arable land were highest, followed by pasture land and forest land. After 13 years continual application of single organic fertilizer or organic fertilization incorporated with chemical fertilizer, total nitrogen content increased by 12.0 %--105.6 % in the top soil （0--20cm）. But no significant differences of total N contents were found in the subsurface layer （20--40cm） in all treatments. The alkali-hydrolyzable nitrogen contents showed a rising tendency with an increase by 32%--299% for each treatment in the top soil which could be attributed to the successive application of organic fertilizer. Soil N was surplus in millet field and was roughly balance in potato fields for all fertilizer applied treatments. N application rate of current crop should be confirmed in terms of N requirement of current crop and the yield of previous crop in the rotation system. As to millet and potato, fertilization should emphasis the N fertilizer and organic fertilizer. The rational application ration of N to P for millet should be 1 to 0.5--0.7 and 1 to 0.7 for potato.