耕作措施和秸秆还田对双季稻田土壤氮渗漏的影响

Effects of tillage and straw returning on nitrogen leakage in double rice cropping field

针对免耕稻田土壤物理性状的改变引起的土壤氮素淋洗问题,通过定位试验研究了不同耕作措施的稻田土壤氮素特征,为免耕稻田氮素的高效利用提供依据。研究在我国双季稻典型区湖南省宁乡县长期定位试验田进行,该试验地自2005年设置免耕秸秆还田(NT)、旋耕秸秆还田(RT)、翻耕秸秆还田(CT)和翻耕秸秆不还田(CT0)4种耕作处理,重复3次。使用定水头法分层测定0～80cm土壤导水率,测定分析各处理80cm处土壤渗漏液铵态氮、硝态氮含量差异。研究结果表明,NT0～80cm土壤的饱和导水率较CT提高了63.14%,NT铵态氮、硝态氮渗漏量显著高于其他处理。秸秆还田措施使早稻耕作覆水初期渗漏水中硝态氮含量显著高于不还田处理。从全年淋失总量估算结果来看,各处理铵态氮渗漏量约是硝态氮的2倍。总之,相对于耕作处理,免耕会使氮素淋失量增加,而长期淹水条件下稻田铵态氮渗漏应得到更多的重视。

Tillage affects the nitrogen leakage by changing soil physical and chemical properties.The effects of tillage on soil permeability and nitrogen leakage were studied for increasing utilization efficiency of nitrogen in paddy field.Long-term field experiments were established from 2005 in a double rice cropping region,Ningxiang county,Hunan province of China.Treatments included no-tillage with straw returning（NT）,rotary-tillage with straw returning（RT）,conventional tillage with straw returning（CT） and conventional tillage without straw returning（CT0）.Constant-head method was used to analyze soil hydraulic conductivity in the soil layer 0-80 cm.Results showed that there was an increase in soil hydraulic conductivity in NT,which was 63.14% and higher than that in CT.Higher leakage of NH4＋-N and NO3--N（p0.05） were found in NT than in other treatments.Straw returning enhanced the leakage of NO3--N,especially in the period of early rice cultivation.The annual leakage of NH4＋-N was almost two times than that of NO3--N among each treatment.Compared with other tillage treatments,NT could increase nitrogen leakage,and more attention should be focused on NH4＋-N leakage in long-term flooding paddy fields.