合理耕层构造提高东北春玉米产量的根—冠碳氮代谢生理生态机制

Altering tillage methods to create different tilth soil structure is one of the important ways to regulate the roots and shoots growth and yield of maize. Maize is the largest crop in China, and the Northeast Plain is the critical producing region in our country. Currently, soil organic matter reducing and quality declining, and tilth soil structure deterioration increasingly, becoming the key factors among the several restricted factors on the yield of spring maize in Northeast. The preliminary study of this project has confirmed that the reasonable tillage can significantly increase the yield of maize, however, the related mechanisms of action are not clear. Therefore, this project intends to a long-term positioning research platform in different tillage methods, the cultivation column simulation, micro-controlled plot, and field long-term positioning experiments will be conducted to study the improving eco-physiological mechanisms of carbon and nitrogen metabolism in roots and shoots in spring maize under ideal tilth soil structure with increasing yield. In the experiments, the root cutting off from different soil depth and isotope tracer (13C and 15N) methods will be used. The roots and shoots are the significant parts for carbon and nitrogen metabolism during the course of ecophysiology in maize, which suggested the roots and shoots must be as one system to under the yield formation. This project focuses on the physiological and ecological mechanism of maize production in order to improve the yield of maize, the following are studied: (1) to explore the critical process during maize roots morphogenesis and senescence under different tilth soil structure, and quantitative description of its characteristics, and explain its biological and physiological mechanisms; (2) to prove the nitrogen absorption, transport, utilization characteristics by roots, to research the photosynthetic properties, product distribution and accumulation by shoots, under ideal tilth soil structure conditions, to clarify the eco-physiological mechanisms of coordination between carbon and nitrogen metabolism in roots and shoots. The goal of this project is to further enrich the theory of maize cultivation, and provide a scientific basis for establishing the ideal tilth soil structure and improving the high-yielding cultivation techniques, to tapping the potential of maize yield in the future.

改变耕作方式创建不同的耕层构造是调控玉米根系与地上部生长发育及产量形成的重要途径之一。目前，制约东北春玉米单产提高的诸多因素中，以土壤有机质“量减质退”和耕层结构恶化问题尤为突出；本项目前期研究已确证合理耕层能显著提高玉米产量，但其作用机制尚不清晰。因此，本项目拟在不同耕法长期定位平台上，采取栽培柱模拟、控制性微区试验和大田长期定位校验相结合的技术路线，运用断根和同位素示踪的方法，从根系与地上部系统角度，围绕合理耕层提高玉米产量的生理生态机制这个核心开展研究：（1）揭示合理耕层调节玉米根系建成和衰老关键过程，定量化描述其特征，阐释其生物学和生理学机制；（2）探明合理耕层提高玉米产量的根系氮吸收、转运、利用及地上部光合性能、产物分配与累积特性，阐明根系与地上部碳氮代谢协调的生理生态机制。通过研究，进一步丰富玉米栽培学的理论，为合理耕层构造创建和高产栽培技术改进，挖掘玉米产量潜力提供科学依据。

通过不同耕作方式创建合理的耕层构造是调控玉米根系与冠层生长发育及产量形成的重要途径之一。本项目在黑土地不同耕法长期定位实验创建的不同耕层构造平台上，运用碳氮稳定性同位素示踪法从根系—地上部系统角度，围绕合理耕层提高玉米产量的碳氮代谢生理生态机制开展了相关研究工作，取得如下主要研究结果。. （1）少耕和免耕处理可以显著提高0-20cm耕层土壤碳氮含量，微生物活性与多样性提高，促进了根系对肥料氮的吸收；（2）玉米籽粒中的氮素分别有13.5%、17.2%和69.3%来源于底肥、追肥和土壤。长期少耕处理玉米根系来源于追肥的氮吸收量和吸收比例较高，茎秆来源于底肥的氮吸收量和吸收比例较高，且茎秆和籽粒的干物重和氮吸收量较高，从而导致其籽粒产量和氮吸收量较高；（3）少耕处理籽粒13C同位素的回收率与分配率显著高于其余各处理，较深翻、免耕和常规垄作处理显著提高10.5%、6.1%和47.6%，说明长期少耕处理能通过促进根系发育进而使得冠层光合产物高效地向籽粒中转运，提高光合碳的利用率；（4）少耕和免耕增加了玉米果穗的百粒重、穗粒数和收获指数，光合产物中碳向籽粒的分配比例较高，从而使得产量构成因素显著提高，获得较高产量主要得益于叶片的光合碳代谢生理显著改善。. 长期少耕和免耕通过构建的合理耕层直接促进了玉米根系发育及氮代谢，改善了冠层的光合碳代谢，为黑土地保护性利用提供了科技支撑。