夏玉米氮磷减量深施对根系构型与生理功能的调控及其增产增效机制

No-tillage and seed-fertilizer simulcasting is one of the simplified and efficient cultivation technique of summer maize and widely been applied in China. However, in this cultivation technique, there are some outstanding problems like large amount of fertilizer input, improper fertilizer ratio, diffused pollution and low use efficiency, which seriously limited the high yield and high resource use efficiency of summer maize. Therefore, this project chooses two elements of nitrogen and phosphorus as key element, and they have significant differences of transferability in soil. We aimed study the regulation effect and mechanism of reduce nitrogen and phosphorus fertilizer input, optimize the depth of fertilization on vertical distribution of nutrients in the soil, maize root plasticity, especially root morphology and architecture, temporal and spatial distribution in soil and function. We will also study the interaction effect of nitrogen and phosphorus on root’s plastic and function. Morphology, physiological and biochemical and isotope tracer technologies will be combined to reveal its physiological mechanism of relieving internal competition of root system, and promotion of efficient economic utilization of photosynthetic assimilation in plants. Importantly, this study will provide the theoretical and technical support for the realization of the high spatial and temporal coupling of root and soil nutrient, and then promote of the synergistic improvement of production and resource utilization efficiency of summer maize.

本项目针对夏玉米种肥同播过程中存在的肥料投入量大、配比不当、面源污染重、利用率低等制约高产高效的突出问题，以土壤中可移动性差异显著的氮和磷两种元素为对象，通过降低氮磷肥料投入、优化施肥深度调控土壤养分的垂直分布，借助形态学和同位素示踪等技术手段，研究肥料减量20%条件下氮、磷及二交互作用对夏玉米根系组成；不同类型根系数量、长度与着生角度；不同类型根系上侧根起始分支位置、密度与长度；根系时空分布等构型指标的调控效应。借助动态离子流检测、分子生物学等技术分析根系对硝酸根和磷酸根离子吸收性能及吸收相关基因的表达量。从形态、生理、生化等多个层面揭示肥料减量适宜深度施用条件下氮、磷及二者交互作用对根系构型与生理功能的调控机理，探明调控高产夏玉米根系与土壤氮、磷时空耦合程度、提高肥料利用效率的可能技术途径，为协同提高产量与资源利用效率，促进夏玉米可持续增产增效提供理论与技术支撑。

玉米单产提高过程中土壤肥力不足和过度依赖施用化肥的问题日益突出，实现作物产量与肥料利用效率协同提高成为当确保粮食安全的主要途径。本项目以登海605为试验材料，设计不同氮、磷用量及施用深度处理，采用大田试验与土柱栽培相结合的方式，对氮磷肥减量深施及其交互作用对夏玉米根系发育及产量形成进行了深入研究。结果表明：（1）氮肥适度深施（-15 cm）有利于促进根系生长，增加深层土壤中根系干重、根长密度、根系吸收面积、活跃吸收面积。同时可优化根系解剖结构，增大根系通气组织所占比例和皮层细胞直径，皮层细胞层数降低16.2%，根系碳、氮代谢成本分别降低6.8%和14.3%。提高根系与土壤氮素分布的空间耦合度，实现氮素高效吸收利用，与常规施氮相比，减少15%施氮量结合15 cm深度施用玉米氮素积累量、氮肥表观利用效率、氮肥农学利用效率和氮肥偏生产力、产量分别增加21.6%、66.7%、38.5%、22.1%和3.9%。（2）磷肥适当深施（-15 cm）显著促进夏玉米根系生长，深层玉米根系生长显著增加随着施磷深度的增加，通气组织所占比例先增加后减少,皮层细胞大小逐渐增加，磷代谢成本和氮代谢成本显著降低了4.0%和3.5%。磷肥深施增加了植株N、P的积累量和向籽粒的转运。磷肥深施处理完熟期干物质提高了12.0%，磷肥表观利用效率、磷肥农学利用效率、磷肥偏生产力及氮肥偏生产力分别提高了150.2%，74.1%，21.2%和21.6%。（3）随施氮磷施用深度的增加，籽粒产量呈先增加后降低的趋势，变化范围为8.7 ~ 12.2 t hm -1。与常规表层施用相比，在降低15%磷用量下，二者深施在-15 cm可以调控玉米根系的形态与功能，促进深层根系发育，提高土壤养分的吸收利用，对于促进植株干物质的积累，实现产量与肥料利用效率协同提升。