太湖地区水稻产量、根圈土壤矿质态氮及氮素径流损失对氮肥的响应

通过氮肥梯度小区试验,研究了施氮对水稻根圈土壤及土壤溶液矿质态氮、叶片SPAD值、氮素累积量、水稻产量和氮素径流损失的影响.结果表明:基肥显著增加了苗期水稻根圈土壤矿质态氮,追肥对水稻根圈土壤及土壤溶液矿质态氮含量影响较小;施氮对水稻顶三叶SPAD值影响较为显著,而不同氮肥梯度下SPAD值无显著差异.分蘖期后,施氮量和植株氮素累积量存在显著正相关关系;收获期秸秆氮累积随着施氮量的增加而增加,但籽粒氮累积受施氮量影响较小.施氮量的增加对水稻增产效果并不显著,却显著提高了总氮径流损失,降低了氮肥农学效率,综合考虑产量、农学效率和总氮径流损失,该地区施氮量需低于理论最高产量施氮量(243 kg·hm^-2);该季135 kg N·hm^-2施氮量处理产量虽有所下降(差异不显著),但其农学效率最高且总氮径流损失最低.针对污染严重区域,在保证产量的基础上采用低氮肥投入而极大限度地降低施氮对环境的潜在污染是可行的.

Responses of Rice Yield, Rhizospheric Soil Mineral N and N Runoff Loss to Fertilizer N in the Tai Lake Region

In this study, mineral N in rhizospheric soil and its solution, SPAD, plant N accumulation, grain yield and N runoff loss were determined under rice grown in six fertilizer N treatments. Results showed that basal N fertilizer significantly increased rhizospheric soil mineral N, but two top dressings had little impacts on mineral N in both soil and soil solution. The SPAD responded well to N fertilizer, but no significant difference in SPAD was found among N treatments. A positive linear relationship existed between N accumulation and fertilizer N rate after tillering stages. Increasing N rates significantly increased nitrogen accumulation in straw at the harvest, but had little impacts on grain N. Rice yield did not always increase with increasing N fertilizer. No significant differences in grain yields were found among N treatments. However, elevated N fertilizer increased total N losses through runoff and decreased the agronomical efficiency of fertilizer N. Considering rice yield, agronomical efficiency and N runoff loss, the recommended maximum N rate should be 243 kg·hm^-2. At 135 kg N·hm^-2, a comparable yield, the highest agronomical efficiency and the lowest N runoff loss could be obtained. Thus, it is feasible to lower N inputs to avoid high N losses from the paddy field in extremely N polluted area.