旱作农田土壤剖面残留硝态氮高效利用的根际调控

Application of a large amount of nitrogen resulted in greater nitrate accumulation in soil profiles and lower nitrate nitrogen recoveries in dryland farmland; therefore, it is very important to explore more efficient ways of using fertilizer nitrogen and soil residual nitrogen. In this project, multi-year field experiments with the dryland spring maize cultivate system will be conducted to study the surface mulching and split nitrogen applications effects on nitrate accumulation and bioavailability in dryland of the Loess Plateau. The content and distribution characteristics of nitrate and roots will be analyzed, to analyze the response characteristics of nitrate accumulation in the soil profile to different mulching and niteogen application in dryland, to reveal the interaction mechanisms of nitrate and root growth. By using 15N tracer study, the project will also aim to identify the recovery of 15N-labeled nitrate injected at different depths of the soil profile under several surface mulching conditions, and to reveal the mechanisms and effects of different root architecture genotypes on nitrate nitrogen use efficiency. On the basis of these, by optimizing placement of phosphorus application, the rhizosphere management measures, which combine soil environment regulation with genotype regulation, will be proposed to improve use efficiency of nitrate nitrogen accumulation in soil profile of dryland farmland. The results of this project will provide new academic ideas and methods for figuring out the contribution of nitrate to crop growth under different mulching. And it will contribute to high and stable yield of dryland agriculture and to maximizing the nitrogen use efficiency in dryland of the Loess Plateau.

项目针对旱作农田硝态氮累积量高利用率低的问题，以黄土旱塬长期田间定位试验、15N标记微区及模拟试验为基础，研究地表覆盖与氮肥运筹对农田土壤剖面硝态氮累积、年际变化及运移特征的互作效应；明确春玉米根系构型对土壤剖面硝态氮累积的响应及不同基因型春玉米根系构型对残留硝态氮利用的差异；阐明在地表覆盖及氮肥运筹条件下作物对残留硝态氮空间异质性的响应特征；揭示施磷位置对剖面残留硝态氮作物吸收利用的调控效应及机制；分析不同根构型基因型与施磷位置对残留硝态氮吸收利用的互作效应；探索提高剖面残留硝态氮生物有效性的根际调控途径。研究不仅可揭示旱作农田硝态氮残留与根系生长的相互作用机制，也为充分挖掘作物根系生物学潜力以提高残留硝态氮利用效率，协同实现旱作高产稳产及氮肥高效利用提供科学依据。

项目针对旱作农田硝态氮累积量高利用率低的问题，以黄土旱塬长期田间定位试验为基础、结合15N标记微区及室内分根模拟，系统研究了地表覆盖与氮肥运筹对旱作春玉米作物产量及农田土壤剖面硝态氮累积、运移及利用的影响。结果表明，地膜覆盖条件下控释氮肥和普通尿素1:2配施处理显著增加春玉米生育期叶面积指数、光能捕获量（PARi）和籽粒产量，3年最高产量分别达14.86、14.77和16.68tha-1。与单施尿素相比，控释氮肥配施增加吐丝前氮素累积量和转移量；与不覆盖和秸秆覆盖相比，地膜覆盖处理增加不同施氮条件下收获期总氮素累积量和转移量，降低了土壤剖面硝态氮累积和深层淋溶风险。不同氮效率品种玉米根系特征参数、ZmNRT2基因表达和硝酸盐吸收速率具有显著的基因型差异。与鲁单981相比，氮高效品种郑单958的主根生长具有明显优势，且根系生长对土壤硝态氮非均匀性分布表现出较强的可塑性，种子根单位根长吸收速率在局部高浓度硝态氮条件下显著增加。地膜覆盖与控释氮肥配施可改变郑单958玉米根系时空分布特征，促进生育后期剖面0-20cm和60-100cm根长密度等，提高植株吸收深层土壤水分和养分的能力，并调控根际土壤碳氮含量和微生物群落特性，显著增加秸秆和籽粒对剖面不同土层残留硝态氮的吸收。与不覆盖和秸秆覆盖相比，地膜覆盖处理20-50cm土层土壤硝态氮平均吸收效率分别增加226.6和106.2%，50-80cm分别增加227.9和111.3%。施氮显著增加籽粒对土壤剖面残留硝态氮的吸收，减少硝态氮向下迁移距离，残留硝态氮吸收效率与标记土层根长密度呈显著正相关关系（p<0.001）。玉米籽粒产量与R1期0-20cm根长密度以及R3和R5期0-100cm土层根长密度呈显著正相关。因此，合适根系构型玉米品种结合覆盖和肥料运筹可减少硝态氮淋溶和增加剖面硝态氮生物有效性，提高籽粒产量和经济效益。研究不仅可揭示旱作农田硝态氮残留与根系生长的相互作用机制，也为充分挖掘作物根系生物学潜力以提高残留硝态氮利用效率，协同实现旱作高产稳产及氮肥高效利用提供科学依据。...