秸秆和肥料管理措施对太湖流域水稻种植氮流失的影响

Effects of Straw and Fertilizer Managements on Nitrogen Loss in Rice Cultivation in Taihu Lake Basin

稻田系统的氮流失是农业面源污染的重要组成部分.当前,氮肥投入量已得到有效控制,针对不同秸秆和肥料管理措施的多途径(径流、侧渗、下渗)氮流失特征研究还较为缺乏.对此,选取太湖流域种植时长超过20 a且持续秸秆还田超过5 a的稻田,研究秸秆和肥料管理措施对水稻全生育期不同途径氮流失的影响,并基于作物产量、氮利用效率及氮流失强度,对秸秆和肥料管理措施的生产适宜性和环境友好性进行研判.结果表明,秸秆离田会提升水稻植株对施氮的敏感度.稻季氮总流失量为9~17 kg·hm^(-2),占氮肥施用量的5%~7%.对秸秆管理而言,秸秆离田的泡田排水具有更高氮流失风险;秸秆还田可降低15%以上的下渗途径氮流失量,但是对侧渗途径的氮流失作用并不明确.对肥料管理而言,有机肥的适宜替代可较同施氮梯度下的化肥施用减少16%的种植期径流氮流失、26%的下渗氮流失,以及37%的侧渗氮流失.综合产量数据,实施秸秆还田和肥料类型优化能够有效降低生产单位重量稻米的氮流失量,切实实现对农业生产和环境友好的双向兼顾.

Nitrogen loss from rice systems is an important source of agricultural non-point source pollution.Many studies revolve around reducing the rate of nitrogen fertilizer application.However,studies examining the characteristics of nitrogen loss in multiple loss paths(runoff,leaching,and lateral seepage)under different straw and fertilizer managements are lacking.Therefore,a study was carried out based on a rice field planted for more than 20 years with straw continuously returned to the field for more than 5 years in Taihu lake basin.The effects of straw and fertilizer managements on nitrogen loss in different paths during the whole growth period of rice were studied.Moreover,straw and fertilizer managements were evaluated by their production suitability and environmental friendliness based on crop yield,nitrogen use efficiency,and nitrogen loss.The results showed that straw removal from the field increased the response sensitivity of nitrogen accumulation in plant tissue to nitrogen application.The nitrogen loss in the rice season was 9-17 kg·hm^(−2),accounting for 5%-7%of the nitrogen application rate.Straw removal increased the risk of nitrogen loss when soaking water discharged.Straw returning could decrease the nitrogen loss by more than 15%,though the effect of straw on nitrogen loss via lateral seepage was not clear.Furthermore,the suitable substitution of organic fertilizer(30%in this study)could respectively reduce the amount of nitrogen loss via runoff,leaching,and lateral seepage by 16%,26%,and 37%compared with the fertilizer application under the same nitrogen gradient.In conclusion,the implementation of straw returning and fertilizer type optimization measures effectively reduced the nitrogen loss for unit weight of rice production and realized the balance between agricultural production and environmental protection.