太湖地区稻田绿肥固氮量及绿肥还田对水稻产量和稻田土壤氮素特征的影响

EFFECTS OF BIOLOGICAL NITROGEN FIXATION AND PLOW-DOWN OF GREEN MANURE CROP ON RICE YIELD AND SOIL NITROGEN IN PADDY FIELD

通过田间试验,利用15N自然丰度法,研究了太湖地区水稻土冬季绿肥的固氮量,以及绿肥还田后配施氮肥对水稻产量、稻田土壤供氮能力及土壤氮素淋失特征的影响。试验结果表明,紫云英和蚕豆当季分别能固定氮约32.8和68.8 kg km-2进入稻田生态系统以培肥土壤和供下季水稻利用。蚕豆秸秆还田后基本能满足水稻生长所需的氮,紫云英和蚕豆还田施氮120 kg km-2时,既可保证水稻较高产量,又节约当季化学氮肥45%～55%。紫云英和蚕豆还田不施氮肥处理,整个生长期耕层土壤溶液NH+4-N、NO-3-N和TN浓度均低于配施氮肥的处理;蚕豆还田处理土壤溶液TN浓度高于紫云英还田处理。随氮肥用量增加,NH+4-N、NO-3-N和TN浓度有增加趋势,不同施氮量间差异不显著。绿肥-水稻轮作,紫云英和蚕豆还田土壤氮素淋溶显著降低。配施氮肥增加了土壤氮的淋失量,尤其施氮300 kg km-2处理,土壤淋溶液NH+4-N、TN浓度显著高于施氮0～240 kg km-2的处理。

A study was conducted on biological nitrogen fixation and plow-down of green manure crops on rice yield and nitrogen dynamics in paddy field in the Taihu Lake Region, using the^15N natural abundance method. Results show that Chinese milk vetch and faba bean biologically fixed about N 32.8 and 66.8 kg km^-5, respectively, in their growth season. Plow-down of green manures as a nitrogen source basically satisfied N requirements of the subsequent rice crop. The application of N 120 kg km^-2 in addition to the plow-down could not only ensure higher rice grain yield, but also reduce the application of chemical fertilizer N by 45% to 55% compared to the common dosage in this region. The treatment of plow-down alone was significantly lower than the treatment of plow-down plus N fertilizer in concentrations of NH4^＋-N, NO3^- -N and TN of the soil solution in the plowed layers during the whole growth season. The treatment of plow-down of faba bean was higher than the treatment of plow-down of Chinese milk vetch in TN concentration in the soil solution. Additional application of chemical nitrogen rendered the concentrations of NH4^＋ -N, NO3^- -N and TN in soil solution a rising tendency, but the effects were not much different between treatments of different application rates. Nitrogen leaching in paddy fields using green manures as the only nitrogen source for rice crop was much lower. With the application of chemical nitrogen, nitrogen leaching increased. The leaching of NH4^＋-N, NO^--N and TN into deep soil water was especially higher in the treatment of N 300 kg km^-2than in the treatment of N 0 -240 kg km^-2.