Nitrate-Nitrogen Dynamics and Nitrogen Budgets in Rice-Wheat Rotations in Taihu Lake Region, China

ZHANG Jun-Hua; LIU Jian-Li; ZHANG Jia-Bao; CHENG Ya-Nan; WANG Wei-Peng

摘要

Nitrate-nitrogen (NO3--N) dynamics and nitrogen (N) budgets in rice (Oryza sativa L.)-wheat (Triticum aestivum L.) rotations in the Taihu Lake region of China were studied to compare the effects of N fertilizer management over a two-year period.The experiment included four N rates for rice and wheat,respectively:N1 (125 and 94 kg N ha-1),N2 (225 and 169 kg N ha-1),N3 (325 and 244 kg N ha-1),and NO (0 kg N ha-1).The results showed that an overlying water layer during the rice growing seasons contributed to moderate concentrations of NO3--N in sampled waters and the concentrations of NO3--N only showed a rising trend during the field drying stage.The NO3--N concentrations in leachates during the wheat seasons were much higher than those during the rice seasons,particularly in the wheat seedling stage.In the wheat seedling stage,the NO~-N concentrations of leachates were significantly higher in N treatments than in NO treatment and increased with increasing N rates.As the NO3--N content (below 2 mg N L-1) at a depth of 80 cm during the rice-wheat rotations did not respond to the applied N rates,the high levels of NO3--N in the groundwater of paddy fields might not be directly related to NO3--N leaching.Crop growth trends were closely related to variations of NO3--N in leachates.A reduction in N application rate,especially in the earlier stages of crop growth,and synchronization of the peak of N uptake by the crop with N fertilizer application are key measures to reduce N loss.Above-ground biomass for rice and wheat increased significantly with increasing N rate,but there was no significant difference between N2 and N3.Increasing N rates to the levels greater than N2 not only decreased N use efficiency,but also significantly increased N loss.After two cycles of rice-wheat rotations,the apparent N losses of N1,N2 and N3 amounted to 234,366 and 579 kg N ha-1,respectively.With an increase of N rate from NO to N3,the percentage of N uptake in total N inputs decreased from 63.9％ to 46.9％.The apparent N losses during the rice seasons were higher than those during the wheat seasons and were related to precipitation; therefore,the application of fertilizer should take into account climate conditions and avoid application before heavy rainfall.

机译：研究了太湖地区水稻（Oryza sativa L。）-小麦（Triticum aestivum L.）轮作中的硝态氮（NO3--N）动态和氮（N）收支平衡，比较了氮肥管理的效果。在两年的时间里，该实验分别包括四个水稻和小麦的氮素含量：N1（125和94 kg N ha-1），N2（225和169 kg N ha-1），N3（325和244 kg）结果表明，水稻生长季节上覆水层有助于采样水中适度的NO3--N浓度和NO3--N浓度。仅在田间干燥阶段才表现出上升趋势。小麦季节渗滤液中NO3--N的浓度要比水稻季节高得多，尤其是在小麦幼苗期。在小麦幼苗期，NO〜- N处理中渗滤液中N的浓度显着高于NO处理，并且随着N的增加而增加。稻麦轮作时在80 cm深度处低于2 mg N L-1）（N L-1）对施用的N速率没有反应，稻田地下水中的高NO3--N含量可能与NO3没有直接关系--N淋失。作物生长趋势与渗滤液中NO3--N的变化密切相关。氮肥施用量的减少，尤其是在作物生长的早期阶段，以及作物吸收氮素的高峰与氮素的同步化施肥是减少氮素流失的关键措施。水稻和小麦的地上生物量随氮素含量的增加而显着增加，但氮素和氮素之间没有显着差异。氮素含量增加至大于氮素含量不仅减少了氮素的使用稻麦轮作两个周期后，N1，N2和N3的表观氮素损失分别为234,366和579 kg N ha-1。 N3，氮吸收量在总氮输入中的百分比从6降低3.9％至46.9％。水稻季节的表观氮素损失高于小麦季节，且与降水有关。因此，肥料的施用应考虑气候条件，避免在暴雨前施用。

Nitrate-Nitrogen Dynamics and Nitrogen Budgets in Rice-Wheat Rotations in Taihu Lake Region, China

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