黄河三角洲盐渍农田土壤氮磷养分增效机理

Migration, transformation processes of soil nitrogen and phosphorus and their bio-availability to crops are significantly affected by its salt-alkali barriers, which seriously restricts the enhancement of soil fertility and nutrient use efficiency of salinized farmland in the Yellow River Delta. Using the indoor temperature-controlled incubation experiment, soil column leaching experiment, in-situ controlled field experiment, stable isotope tracer experiment and regional monitoring approaches, this project are to: a) investigate key factors inhibiting nitrogen and phosphorus nutrient utilization of salinized farmland in the Yellow River Delta, clarify the restriction mechanism of soil salinity on crop’s nitrogen and phosphorus utilization; b) explore the key processes of ammonia volatilization inhibition, nitrogen loss control, assimilation promotion and microbial fixation of salt-affected soils, illuminate the regulation mechanism of loss deduction and holding enhancement of nitrogen nutrient in salinized farmland; c) examine the key processes of phosphorus transformation, microbial activation and crop uptake promoting of salinized farmland, distinguish the activation synergistic regulation mechanism of phosphorus nutrient in salinized farmland; d) analyze the conjunctive promotion effects of salinity alleviation on nitrogen and phosphorus nutrients retention and leaching reduction in salinized farmland, reveal the mechanism on nutrient enhancement of soil nitrogen and phosphorus by comprehensive water-fertilizer-salt regulation processes of salinized farmland in the Yellow River Delta. Current research will provide important theoretical basis for resolving key scientific problem of coordination of salinity obstacle reduction and the synergistic regulation of nitrogen and phosphorus of salinized farmland, for improving the nutrient utilization efficiency, for accelerating saline-alkali barriers reduction and for enhancing the land productivity in the Yellow River Delta.

盐碱障碍影响农田土壤中氮磷养分的迁移、转化过程及其有效性，严重制约了黄河三角洲盐渍农田地力和养分利用效率的提升。项目采用室内恒温培养、土柱淋溶模拟、田间原位控制试验、稳定同位素示踪与区域监测等方法与手段，研究影响黄河三角洲盐渍农田氮磷养分利用的主控因子，明晰土壤盐渍化制约氮磷养分利用的作用机制；研究盐渍土壤的氨挥发抑制、氮流失阻控、氮素同化促进与微生物固定等关键过程，探明盐渍农田氮素养分的减损增持调控机制；研究盐渍化土壤磷素形态转化、微生物活化与作物吸收促进等关键过程，阐明盐渍农田土壤磷素活化增效调控机制；研究盐渍农田障碍消减与氮磷养分固持阻淋及氮磷养分协同的促进效应，揭示黄河三角洲盐渍农田氮磷养分协同增效的水-肥-盐复合调控机制。本研究将为解决农田障碍消减与氮磷养分增效的协同调控等关键科学问题，提高黄河三角洲盐渍农田养分利用效率、加速盐碱障碍消减和提升地力提供重要理论基础。

盐碱障碍影响农田土壤中氮磷养分的迁移、转化过程及其有效性，严重制约黄河三角洲盐渍农田地力和养分利用率。项目采用室内恒温培养、土柱盆栽模拟、田间原位试验，结合15N稳定同位素示踪、定量PCR扩增、高通量测序等方法与手段，研究了黄河三角洲盐渍农田养分利用的关键障碍因子，解析了氮素养分减损增持调控机制，阐明磷素活化增效调控机制，揭示水-肥-盐复合调控氮磷养分协同增效机制。研究发现：（1）土壤盐分含量及离子组成是抑制有机氮矿化、尿素水解、硝化的主因，氮淋失和氨挥发均随盐分升高而增大；土壤磷素转化主要受质地和pH影响，且氮磷之间存在颉颃效应，施氮抑制磷素的释放与生物有效性，尤其是Ca2-P和Ca8-P的含量。（2）土壤盐分通过延长氨挥发、氮转化持续时间和抑制作物吸收增加NH3挥发量和氮淋失量，灌溉、水分管理、有机肥和黄腐酸等措施通过降低土壤盐分、pH，改变AOA、AOB和CAOB群落组成、活性以及Coprinellus、Mortierella、Funneliformis属相对丰度，直接或间接地促进土壤微生物量氮固持。（3）土壤盐分通过降低活性无机磷、升高稳定性无机磷而降低土壤磷素有效性；盐渍障碍消减提升或改变Povalibacter、Gimesia、Hyphomicrobium、Sphingomonas等属功能微生物的丰度、活性，促进盐渍农田解磷活化；有机酸/盐对磷素活化具有正向激发效应，作用大小为三元>二元>一元酸（盐）；生物炭加入对磷素起负激发作用，使磷素趋向更稳定形态。（4）覆盖和隔层通过改变土壤结构和导水性能抑制盐分上行并消减盐碱障碍，生物炭和抑制剂、适宜氮磷配比有利于提高氮磷肥利用率；综合考虑黄河三角洲盐渍农田障碍消减、地力培育、养分减损增持与作物高效吸收的多目标，提出了“覆盖+隔层”降低土壤水盐胁迫、氨挥发与氮淋失，利用“有机无机配施（25-30%化肥有机替代）+生物炭+黄腐酸”生物激发促进养分固持利用的水-肥-盐复合管理方案。本研究为解决农田障碍消减与氮磷养分增效的协同等关键科学问题，提高黄河三角洲盐渍农田养分利用率、加速消减盐碱障碍和提升地力提供重要理论基础。