宁夏黄灌区稻秆还田对硝态氮流失量的影响

为控制稻田土壤硝态氮流失,对宁夏黄灌区稻田设置不同量秸秆还田处理常规施肥不还田（CK）、常规施肥条件下稻秆分别半量（T1）与全量（T2）还田,采用树脂芯法测定了稻秆还田10、20、30cm土层硝态氮淋失量。结果表明,稻秆还田可以有效减少30cm处硝态氮淋失量,减少比例在5.5左右。从生育期内来看,前期流失量大于后期,但在后期120cm土层渗滤液中硝态氮含量在10mg.L-1以下,对地下水污染没有威胁。稻秆还田条件下,前期土壤硝态氮含量较低,减少了硝态氮淋失的可能性,后期N素得到释放而促进了水稻的生殖生长,产量得到增加。因此,稻秆还田可以作为源头控制稻田硝态氮流失的较好措施加以推广。

The Influence of Rice Straw Returning on the Leaching Losses of the Nitrate Nitrogen in Ningxia Irrigation District,China

Ningxia Irrigation District is the representative irrigation farming region in the upper stream area of the Yellow River.The paddy-upland rotation is still the typical agricultural model in this irrigation district.The crude farming methods are used in the paddy planting,such as uncontrolled irrigation and excessive fertilization,therefore there is a high accumulation of the residual nitrate nitrogen in soil after the harvest.A filed experiment was conducted in paddy of Ningxia Yellow River Irrigation District with three treatments including normal fertilization（CK）,half returning（T1） and total returning（T2）,respectively,on the basis of the normal fertilization.The leaching losses of nitrate nitrogen in the depth of 10,20,30 cm was measured by the method of resin core.The result showed that the leaching losses of 30 cm were reduced effectively by straw returning,the decrease ratio of leaching losses was about 5.5%.The leaching losses of nitrate nitrogen was bigger in previous than later during the growth period.The concentration of the nitrate nitrogen in the 120 cm soil percolate was under 10 mg·L-1 in the later period,there was no threat to the groundwater pollution.The results indicated that rice straw returning could reduces the content and the probability of the soil nitrate nitrogen leaching in earlier stage,promotes the vegetative growth of the paddy by releasing the nitrogen in the later stages,and increases the yield.Therefore,the rice straw returning should be popularized for the source control of the nitrate nitrogen loss from paddy field in Ningxia Irrigation District.