根层补灌对冬小麦水氮利用的调控机制

The shortage of water has become one of the important limiting factors in wheat production in Huang-Huai-Hai plain. There are many previous studies show that the demand of soil moisture in different stages by winter wheat for growth and yield formation are different. The growth and distribution of root are affected by the distribution of soil moisture in soil profile, and then, the water consumption characteristics in field and grain yield of wheat are also different. This project based on the previous studies, according to the characteristics that more water is stored in the lower soil layer in wheat field of Huang-Huai-Hai plain, with different genotype wheat cultivars in yield and water-use efficiency, using the technology of supplemental irrigation within different depths of root layer at key growth stages, plans to expound the mechanism of regulation of water and nitrogen use in winter wheat by supplemental irrigation within root layers, and to create the new water-saving cultivation way to achieve high-yield and high water-use efficiency, by studying the physiological and molecular biological basis and the adjustment effect of the water supply level in a certain depth of root layer on growth and distribution of root, yield formation and water-use efficiency, studying the physiological basis and the function of the changes of soil moisture in a certain depth of root layer in adjusting the relationship between the ultilzation of water from lower soil layers and the absorption and ultilization of nitrogen from upper root layers. It is of important theoretical and practical value to save water, increase yield, water-use efficiency and nitrogen-use efficiency.

水资源不足已成为黄淮和北部冬麦区小麦生产的重要限制因素。前人研究表明冬小麦生长和产量形成对不同生育时期的土壤水分含量需求不同；土壤剖面水分分布的不同会引起根系生长和分布的差异，麦田耗水特性和小麦籽粒产量等亦随之改变。本项目在前期研究的基础上，根据黄淮和北部冬麦区麦田中下层土壤贮水较多的特点，选用产量和水分利用效率不同的基因型小麦品种，通过关键生育时期根层补灌，探索不同生育时期一定深度根层水分供给水平对小麦根系生长和分布、产量形成和水分利用效率的调节作用及生理和分子生物学基础，不同生育阶段一定深度根层土壤水分时空变化在调节小麦对深层土壤贮水利用与其对上部根层氮素吸收利用关系中的作用及生理基础，阐明不同深度根层补灌对冬小麦水氮利用的调控机制，探索出实现小麦高产高水分利用效率的新的节水栽培途径，对节约水资源、提高单产和水氮利用效率具有重要的理论意义和实践价值。

水资源不足已成为黄淮和北部冬麦区小麦生产的重要限制因素。前人研究表明，冬小麦生长和产量形成对不同生育时期的土壤水分含量需求不同；生育期内供水时间和数量的差异会导致小麦耗水特性和产量的明显变化。本项目在前期研究的基础上，根据该地区自然降水和麦田土壤贮水特点，探索一定深度根层水分供给水平对小麦根系生长和分布、产量形成和水分利用效率的调节作用及其生理基础；不同生育阶段一定深度根层土壤水分时空变化在调节小麦对深层土壤贮水利用与其对上部根层氮素吸收利用关系中的作用和生理基础；研究揭示不同深度根层补灌对冬小麦水氮利用的调控机制。结果表明，小麦全生育期消耗的土壤水72%-77%来自0-100 cm土层。根系在深层土壤的分布数量主要受越冬前供水的影响。拔节期耕层土壤含水量过低会抑制劣势蘖生长，因干旱导致的劣势蘖的衰亡不能因复水而停止，最终降低成穗数。拔节期根层补灌不仅能优化一定深度土体的供水结构，而且显著提高0-20 cm土层根表面积，促进植株对耕层水氮的吸收利用，这是实现小麦产量和水氮利用效率同步提高的关键技术途径。灌浆后期上部根层含水量过高，虽然叶片ABA含量较低，植株衰老延迟，但营养器官临时贮存的碳氮同化物向籽粒中的转运量明显减少，产量和水分利用效率并不高。小麦开花后叶片光合速率和实际光化学效率均与水分利用效率呈显著正相关，而气孔导度和电子传递速率与水分利用效率无明显相关关系，这进一步阐释了过多灌水不能增产且降低水分利用效率的原因。小麦生育后期上部根层含水量过低虽能增加对深层土壤贮水的利用，但是并不能因此提高水氮利用效率。适时适量根层补灌显著增加开花前植株氮素积累及其向籽粒中的再分配数量，促进开花后氮素的同化和积累，能以较少的氮素投入，获得较高的籽粒产量。依此理论，创新出冬小麦按需补灌水肥一体化技术，为节约水资源、提高单产和水氮利用效率提供了重要理论和技术支撑。