丹江口库区覆膜耕作土壤净氮矿化随夏玉米生长期的变化

Temporal variation of soil net nitrogen mineralization in summer maize growing period under plastic film mulched cultivation in Danjiangkou Reservoir Area,China

农田土壤净氮矿化对土壤氮素流失和农业非点源污染有重要影响.以丹江口库区五龙池小流域夏玉米黄棕壤为例,进行原位矿化试验,通过与无覆膜耕作土壤相比较,研究覆膜耕作条件下土壤净氮矿化在夏玉米生长期内的变化.结果表明:夏玉米整个生长期内,覆膜耕作土壤净氨化量、净硝化量和净氮矿化量均明显高于无覆膜土壤,分别高6.63、12.96和19.59mg·kg^(-1);覆膜耕作土壤净氨化速率表现为在苗期较高、抽穗期最低、成熟期增至最高的变化特征,而土壤净硝化和净氮矿化速率均呈现苗期较高、拔节期最低、成熟期升至最高的变化过程;覆膜耕作土壤净氮矿化速率均与土壤全氮和NO_3^--N含量、土壤含水量之间呈显著线性关系.覆膜可有效调节土壤水热条件,促进土壤净氮矿化.

Soil net nitrogen mineralization in cropland has a great influence on both agricultural non-point source pollution and soil nitrogen loss. A field plot experiment was conducted to explore the temporal variation of soil net nitrogen mineralization under plastic film mulching ridge-furrow in Wulongchi small watershed during summer maize growing period. Results showed that the soil net ammonification, nitrification, and nitrogen mineralization were significantly greater than those of non-mulched treatment, and the differences were 6.63, 12.96 and 19.59 mg ~ kg-~, respectively. During the summer maize growth period, the rate of soil net ammonification was high at seedling stage, low at heading stage, and high at maturation stage. Both the rates of soil net nitrification and nitrogen mineralization were at jointing stage, low at heading stage. The rate of soil net nitrogen mineralization under plastic film stage, and high at maturation mulched had significant linear relation with the contents of soil total nitrogen, nitrate nitrogen, and soil water. In conclusion, the improved condition of soil water and temperature under plastic film mulched cultivation of summer maize in the growing period promoted soil net nitrogen mineralization.