不同施氮量对菜-稻轮作土壤硝态氮累积的影响

Effects of nitrogen application rate on soil nitrate nitrogen accumulation under vegetable-paddy rice rotation system

为了研究氮肥对菜．稻轮作的作物产量和土壤硝态氮累积的影响，开展了芥菜．结球甘蓝一早稻轮作制2年定位田间试验．结果表明：取得最佳经济效益的施氮量为芥菜和结球甘蓝各施N150kg·hm-2、早稻施N90kg·hm-2，净增收比其他施氮水平提高了0．2％-75．6％．施氮量与土壤硝态氮浓度及土柱渗漏水硝态氮浓度均呈线性正相关关系，蔬菜和水稻轮作降低了土壤氮素盈余数量；最佳施氮模式下，芥菜-结球甘蓝-早稻轮作时土壤硝态氮浓度平均为29．7mg·kg-1，只有芥菜．结球甘蓝连作的84．4％；与基础土壤相比，菜．菜．稻轮作时的土柱渗漏水硝态氮平均浓度差异很小．因此，菜．稻轮作结合最佳施氮模式在取得最佳经济效益的同时，显著降低了土壤硝态氮累积，是菜田氮素面源污染控制的有效方法．

A 2-year field experiment of mustard-cabbage-early rice rotation was conducted to inves- tigate the effects of nitrogen application on yield and accumulation of nitrate nitrogen in the soil. The results showed that the applications of 150 kg N ·hm-2 for mustard and cabbage respectively and 90 kg N· hm-2 for early rice were the best economic application mode, which could increase the net profit by 0.2% -75.6% compared with other application modes. Nitrogen application rates were positively correlated with NO3--N concentration in the soil and in the percolating water. The vegetable-paddy rice rotation decreased the surplus of nitrogen in the soil. The average soil NO3--N concentration was 29.7 mg ~ kg-1 under the rotation of mustard-cabbage-early rice, which was only 84. 4% of that under the continuous cropping of mustard-cabbage. The average NO3--N concentra- tion in the percolating water under mustard-cabbage-early rice rotation was little different from that in basal soil. Therefore, with the optimum nitrogen application mode, the vegetable-paddy rice ro- tation could gain the best economic benefit while significantly decrease the accumulation of nitrate nitrogen in the soil to effectively control non-point source pollution of nitrogen from vegetable fields.