丹江口库区覆膜耕作土壤氮素淋失随夏玉米生长期的变化

土壤氮素淋失是农业非点源污染的重要形式,也是水源地水质恶化的重要原因.以丹江口库区五龙池小流域为研究区,以农田黄棕壤种植夏玉米为例进行田间氮素淋失实验,通过与无覆膜耕作进行对比,研究覆膜耕作条件下土壤氮素淋失随玉米生长期的变化.结果表明,覆膜耕作土壤TN和NO_3~--N淋失量均明显低于无覆膜耕作,分别低25.68%和20.25%.夏玉米生长期内,覆膜土壤TN淋失量表现为苗期最高,拔节期和抽穗期显著降低,成熟期略微升高的变化趋势;覆膜土壤NO_3~--N淋失量表现为在苗期最高,拔节期显著降低,随后缓慢降低的变化过程;覆膜土壤NH_4~+-N淋失量表现为在苗期较低,拔节期升至峰值,抽穗期降至谷值,成熟期显著升高的变化特征.覆膜土壤TN和NO_3~--N淋失量分别与土壤中TN和NO_3~--N含量之间呈线性函数和指数函数关系;与土壤含水量和降雨量之间呈线性函数关系.上述结果表明,覆膜能降低土壤中氮素的淋失量,将对减少库区农业非点源污染具有明显的作用.

Change of Soil Nitrogen Leaching with Summer Maize Growing Periods Under Plastic Film Mulched Cultivation in Danjiangkou Reservoir Area, China

As an important form of agricultural non-point source pollution, soil nitrogen leaching deteriorates water quality. Compared with non-mulching cultivated land, field experiment explored the change characteristics of soil nitrogen leaching under plastic film mulching ridge-furrow in Wulongchi small watershed during summer maize growing period. The results showed that the amounts of mulching tillage soil TN and NO₃^--N leaching were significantly lower than those with non-mulched treatment, by 25.68% and 20.25%, respectively. With the advance of the summer maize growth period, leaching amount of mulched soil TN was highest at seedling stage, lowest at heading stage and higher in maturation period; leaching amount of mulched soil NO₃^--N was highest at seedling stage, lowest in maturation period; leaching amount of mulched soil NH₄⁺-N was lower at seedling stage, increased to the peak at the jointing stage, decreased to the valley value at heading stage, and obviously increased in maturation period. Linear function relationship was found between mulched soil TN leaching and TN content, while exponential relationship was found between mulched soil NO₃^--N leaching and NO₃^--N content. In addition, there was linear function relationship of mulched soil TN and NO₃^--N leaching amount with soil moisture and rainfall. It was concluded that the plastic film mulched on summer maize could reduce the leaching loss of soil nitrogen, and it would have a significant effect on the reduction of reservoir area of agricultural non-point source pollution.