黄土高原土壤——植物系统氮素循环研究

Studies on Nitrogen Cysle in Soil-plant Ecosystem of the Loess Plateau Group of Nitrogen Fund

黄土高原耕作土壤含氮0.010—0.120%,平均0.065%。表层土壤矿化的硝态氮(NO_3-N)为30.4—93.2kg/ha,平均53.2kg/ha。土壤氮水平普遍较低是农业生产中的一个大的问题。研究表明,土壤—植物系统每年输入氮105.1kg/ha,输出111.1kg/ha,亏损6kg/ha,这就使得土壤氮素呈缓慢的下降趋势。林地开垦为农地后,氮素下降情况尤为明显。按1m土层土壤贮氮量的多少,将黄土高原划为5个分区,并提出了改善土壤—植物系统氮素循环的重要措施。其中包括把资源—生态—人口—粮食—环境统筹考虑,控制水土流失,增加有机与无机氮的投入。在集约农业经营区,应防止化肥氮的过量施用,以免浪费氮源、污染环境。

The content of nitrogen in cultivated soil of the Loess plateau range from0.010～0.120% with an average of 0.065% and amount of NO_3-N minerali-zated in surface layer of soil varies from 30.4～93.2kg/ha with an average of53.2kg/ha.The generally low lever of nitrogen in soil is a major problemin crop production.Studies on N cycle in soil-plant ecosystem shows that anitrogen deficit of 6kg/ha hsa been observed from which an amount of nitro-gen imported is 105.1kg/ha aud export is 111.1kg/ha.This causes a ge-neral trend to slow reductiou of nitrogen in many soils.Especially an amountof uitrogen in soil of forest area is obviously reduced after bringing the forestland under cultivation.The whole land of the Loess plateau is divided intofive regions based on an amount of N in 0-1 m horizen of soil and the im-portant measure has been worked out in order to improve the cycle of nitrogenin soil-plant ecosystem.It consists of the problems of resources-ecology- population-cereal-euvironment to be taken into an allround consideration,controllingsoil and water lose and increasing the investment of organic and chemical nitro-gen.In the intensive farming area the chemical nitrogen fertilizer applied shouldnot surpass the required amount so as not to waste nitrogen resources andpoll-ute the environment.