摘要:自20世纪90年代以来，持续过量氮磷化肥投入导致农业面源污染日益严重，了解农田土壤氮磷淋溶特征是降低地下水污染的基础。基于田间调查、长期定位肥料试验和田间试验，分析褐土区氮磷的盈余状况，阐明该区农田土壤氮磷的盈余变化、淋溶特征；评价田间管理措施对农田土壤氮磷淋溶的影响。结果表明，典型褐土区关中平原过量施氮的土壤达到83%以上，大量土壤硝态氮已经迁移到100 cm土层以下，15%的水井地下水的硝态氮含量超过10 mg·L-1（WHO饮用水标准）；80%耕层土壤有效磷（Olsen-P）含量已超过20 mg·kg-1，富磷土壤已出现可溶性磷素向耕层以下迁移的现象。氮肥和磷肥的投入量、氮磷吸收量和土壤氮磷残留量之间存在着3个发展阶段：环境友好-资源高效阶段、环境低风险-资源低效阶段和环境有害-资源无效阶段。与当地常规水肥投入量相比，在保证产量的前提下，化肥减量、降低灌溉量、施用生物炭或秸秆还田都可以降低氮磷淋失量；其中化肥减量、降低灌溉可显著降低氮磷的淋失，其次是施用生物炭和秸秆。施用秸秆条件下，阻控硝态氮淋失与微生物生物量碳氮的提高、土壤硝化势降低或反硝化势升高有关。此外，需要关注褐土区粮果复合系统中土壤氮磷淋溶的环境效应、地下水硝酸盐污染的溯源等问题。
关键词:褐土区/
农田土壤/
蔬菜地土壤/
氮磷淋失/
阻控措施
Abstract:Excessive application of nitrogen (N) and phosphate (P) fertilizers have increasingly caused agricultural nonpoint source pollution and groundwater contamination in China since the 1990s. Understanding N and P leaching is critical for reducing groundwater contamination. Field survey data, long-term experimental data, and recent experimental results were used to investigate N and P leaching from arable cinnamon soil across northern China. The results suggested that wheat and corn yield decreased with increasing N or P fertilization in a wheat-corn rotation system. Large amounts of nitrate accumulated in the soil across the region, and the accumulation amount and its downward movement was a potential risk to groundwater. The Olsen-P surplus (>20 mg·kg-1) accounted for 80% of the arable soils in the region. There were strong relationships between NP fertilization rates, crop yield, and residual NP amounts and were into three phases: efficient NP-environmentally friendly phase, low NP efficiency-environmentally low risk phase, and inefficient NP-environmentally harmful phase. Optimized water and fertilizer use ensured crop yield, improved nitrogen use efficiency, and reduced nitrogen leaching losses, but the effects of biochar application and straw incorporation were inconsistent. The nitrate leaching-preventing effects of crop straw incorporation was resulted from soil microbial biomass increase, nitrification potential decreased or denitrification potential increase. Other issues also require investigation, such as tracing regional sources of underground water nitrate pollution, the effects of legacy NP accumulation from excess river anthropogenic inputs, and the environmental consequences of legacy NP accumulation in crop-fruit ecological agriculture.
Key words:Cinnamon soil area/
Cropland soil/
Vegetable land soil/
NP leaching/
Mitigation measures
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