盐碱地膜下滴灌根区土壤水-盐-气作用规律及棉花生长响应关系研究

Abstract: Soil moisture, salinity, and gas are the main environmental factors affecting cotton root system growth. Understanding interactions of these factors under mulched drip irrigation, the response of cotton root growth to the interactions, the threshold of these factors for cotton growth, and how to regulate these factors by irrigation are the main objectives for this project.For saline-alkali land in Xinjiang, through potted plants, soil column, and field experiments, this project is to study the effects of the interactions of soil water, salinity and gas on the distribution and activity of cotton roots, reveal the response of cotton growth to the interactions, and explore the suitable conditions of soil water, salinity and gas for cotton growth in order to facilitate cotton growth and improve productivity. This project is helpful to understand theoretically the interactions of soil water, salinity and gas and its role in regulating cotton growth as different stages, and clear the response of roots to soil water, salinity and gas. Exploring through control of root zone water supply, regulating changes of salinity, gas and root and plant growth, with water and salt, exploring water and gas on the basis of theory, for the realization of high-yielding cotton provide reference for formulating the irrigation system, as well as mode of agricultural water saving agriculture provide a basis for comprehensive control of greenhouse gases.

土壤水分、盐分和气体是影响棉花根系生长的重要环境因素，在膜下滴灌条件下各因子之间如何相互影响，棉花根系和植株生长有怎样的响应关系，对棉花根系生长而言各因子合适的阈值是多少，如何通过灌溉途径调节，这是项目拟解决的问题。针对新疆盐碱地条件，通过盆栽和土柱试验，研究膜下滴灌棉花根区水-盐-气互相作用规律，分析土壤水-盐-气耦合作用对棉花根系在土壤中的分布特征、根系活力的影响，揭示棉花生长的响应关系，探索棉花生长适宜的水-盐-气环境条件，促进棉花健康生长，提高产量。开展本项目研究，有助于从理论上认识膜下滴灌根区水-盐-气相互作用规律以及对棉花不同阶段生长的调节作用，明确根系对水-盐-气环境的响应机理，探寻通过控制根区水分供应，调节盐分变化、气体变化及根系和植株的生长。在以水调盐的基础上探索以水调气理论，为实现棉花高产制定合理的灌溉制度提供参考，同时为农业节水模式下农田温室气体的综合控制提供依据

项目采用土柱试验、桶栽试验和大田试验针对灌溉对土壤盐分变化、气体变化以及水分盐分气体与棉花生长的相互影响开展研究，采用气相色谱仪、土壤呼吸仪测定CO2浓度和通量，采用LCpro+便携式光合测定仪测定棉花净光合速率等指标。主要结果如下：.（1）灌溉对土壤气体的影响。植棉土壤CO2浓度在30cm土层以下随着深度增加表现为幂指数关系，表层10cm、20cm处则规律性较差。灌溉后土壤活性有机质含量发生变化，土壤微生物总量增加了14倍，对土壤CO2的排放也有影响。随着灌溉水量增加土壤CO2通量增加，随着土壤深度增加土壤CO2浓度增加幅度变小。同质地土壤条件下，土壤CO2浓度随着灌溉频率的增加而减小；砂土CO2浓度的增幅高于壤土。.（2）温度对土壤气体的影响。植棉土壤不同深度气体浓度日变化规律明显，未植棉土壤二氧化碳浓度变化规律性较差。在棉花生长进入花铃期后，40-50cm土层处出现高CO2浓度区。植棉土壤温度对于土壤CO2浓度影响贡献为66.8%~72.3%；未植棉土壤温度对于土壤CO2浓度影响贡献为68.1%~80.5%，植棉环境下土壤和温度共同对土壤CO2浓度起作用，未植棉土壤主要是温度起作用。发现土壤温度和土壤含水率对土壤CO2浓度也有一定的交互影响作用。.（3）盐分对土壤气体的影响。砂土和壤土不同盐分含量处理下土壤CO2浓度随着盐分含量的增加而减小。在同一盐分含量条件下，两种土壤质地类型的土壤CO2浓度总体表现为壤土>砂土。在不同盐分含量处理下，花铃期壤土比砂土土壤CO2浓度高。.（4）棉花生长与土壤呼吸的关系。种植棉花垄上的排碳量和固碳量高于垄间。植棉土壤呼吸排碳量是未植棉的3.65倍。棉花根系活力、根长密度和根表面积分别解释了土壤CO2浓度变化的85.4%、77.1%和79.5%。土壤CO2浓度与Pn、Tr、Gs和Ci之间关系密切，植株光合作用对根系土壤呼吸有影响，进而影响土壤CO2浓度。