提高农田水分利用效率的调控机制

提高作物水分利用效率是解决农业淡水资源匮乏的重要途径。本文从水氮调控作物叶片和群体耗水过程、根系调控提高土壤水分的有效性和遗传改良提升作物水分利用效率3个方面论述了国内外研究进展,并提出华北粮食作物生产中通过上述3个方面提升农田水分利用效率存在的问题及对策,为提升华北严重缺水区主要作物农田水分利用效率提供参考。主要包括:1)通过调控有限灌溉农田水分的时空分布,优化地上、地下干物质形成、分配,提高单位农田耗水的生产效率,是充分发挥农田节水潜力的一个重要途径;2)在华北对于压实严重且影响作物生长的土壤上,研究深耕深松结合轮作制度改良上层和下层土壤压实,促进根系生长,对改善长期大型机械耕种可能对作物产生的不利影响有重要意义;3)华北主要作物冬小麦和夏玉米通过品种更新来实现水分利用效率提高的幅度在减小,急需通过高水效品种选育突破,降低品种的生理需水量,实现进一步增产节水目标。

Regulating mechanisms for improving farmland water use efficiency

The North China Plain (NCP) is one of the most important grain production areas in China. With decreasing supply of the limited water resources, the challenge for more grain production on less water via high water use efficiency (WUE) has never been so great in the NCP. A large gap has remained between actual WUE in the NCP and that under optimized agronomic practices. This has called strategies to either maintain or increase agricultural production with less water use. This paper examined the problems that have restricted improvements in WUE in the NCP. It further reviewed three aspects to improve WUE via regulating crop water use in the plain. One aspect was using water-nitrogen interactions to regulate instantaneous and time-integrated WUE at the leaf-canopy level. This also regulated carbon assimilation and allocation in leaf-plant-canopy system and above/below-ground systems. It in turn optimized the processes of biomass accumulation and allocation in grain production and led to the development of field management strategies for optimizing WUE. The second aspect was the management of root system for efficient utilization of soil water. Long-term mechanical tillage practices in the NCP had altered soil physical properties in the top soil layer, which had restricted deep root growth. It was necessary to adopt changes in tillage practices suitable for more efficient utilization of soil moisture by crops. The third aspect was using cultivars with traits for more efficient water use. WUE increased substantially with recent use of early-release cultivars in the NCP. There had also been larger variations in yield and WUE among modern cultivars. Positive correlations between grain yield and WUE indicated that high-yield cultivar had the potential to improve WUE, thereby saving more of the limited water resource in the plain for environment/other uses.