海河流域作物－土壤系统中作物氮的输出

A STUDY ON N OUTPUT IN CROP-SOIL SYSTEM IN HAIHE BASIN Huang Yinxiao Lin Shunhua

本文研究了海河流域地区作物－土壤系统中作物氮素的输出归还量及土壤库存量。结果指出：不同作物氮的输出量和归还量差异很大，１５种作物中以谷子的输出量最大，每年达１１５１ｋｇ／ｈｍ￣２，水稻和莜麦最低，每年输出约３１和６．２ｋｇ／ｈｍ￣２。氮的归还量也以谷子最高，达６８．７３ｋｇ／ｈｍ￣２·ａ，向日葵最低，只２．７４ｋｇ／ｈｍ￣２·ａ。大部分作物都是输出量高于归还量。两者的比值不同作物有显著差异，大豆、棉花、谷子氮的输出量分别为归还量的２１、２０、１７倍，其余作物输出量一般为归还量的２－６倍，说明本区作物－土壤系统输出的氮素较多，归还的氮素较少。本区耕作土氮的平均库存量为１７４９．４３ｋｇ／ｈｍ￣２·ａ，以种植马铃薯、白菜、高粱的土壤的氮库存量较高，分别为３０３７．５、２０２７．０、２３１７．５ｋｇ／ｈｍ￣２·ａ；小麦土、芝麻土氮的库存量较低，只１１９２．５ｋｇ／ｈｍ￣２·ａ。不同作物土壤氮的库存量都高于作物的输出量，土壤氮的库存量为作物输出量的８倍。但作物从土壤中吸收的有效氮是有限的，必需通过施肥补充土壤因作物带走、氮挥发、淋失等被损失的氮。根据上述研究结果，提出维持本区作物－土壤系统氮素的平衡的意见，为本区合?

his paper discusses the nitrogen output and revert amount in plant-soil system in HaiheBasin. The results show that the nitrogen output and revert amount of different crops are ev-idently different. Among the fifteen crops, Panicum miliaceum has the highest N output,which ,is 1151 kg/hm￣2·a,while Orvza satival and Avena nuda are lower,which are 31 and6. 2kg/hm￣2·a. The N revert amount in Paniceum milliceum is also the highest, which is68. 73 kg/hm￣2·a, while the N revert. amount in Helianthus annuus is the lowest, which isonly about 2. 74kg/hm￣2·a. In most of the crops, the N output amount is higher than therevert amount. The proportion of them is significantly different in different crops. The Noutput amount in soybeen, cotton and millet is 21,20, 17 times higher than the revert amountrespectively. In the other crops, the former is 2-6 timse higher than the latter, This showsthat the N output is more than the N revert in the crop-soil system in Haihe Valley. The av-erage N reserve in the cultivated soils of this area is 1749. 43 kg/hm￣2·a. The soils in whichpotatoes, cotton and sorghum are planted have higher N reserve, which are 3037. 5kg/hm￣2·a, 2027. 5kg/hm￣2· a and 2317. 5kg/hm￣2· a respectively. But the soils in which wheat andsesame are planted have lower N reserve, which is only 1192. 5kg/hm￣2·a. We can seeclearly that the N reserves in different soils are higher than the N outputs of the crops plant-ed and the former is about 8 times of the latter. However, the available nitrogen which cropscan absorb from the soil is limited , because nitrogen may volatilize or be carried away by thecrops and water runoff. So we must supplement nitrogen by applying fertilizer. According tothe above-mentioned results, a suggestion for the maintaining of the N balance in HaiheBasin was put forward which will provide a scientific basis for us to apply N fertilizer ratio-nally, making a fuller use of it. and thus raise crop production.