增氧地下滴灌对作物土壤通气性的改善效应

Subsurface drip irrigation (SDI) can deliver oxygen and water to the plant root zone through the use of a Venturi tube entraining air into the water stream. This technique of incorporating pure oxygen or air into irrigation water for aeration of the rhizosphere is termed as aerated SDI. Aerated SDI has been reported to produce positive response on crop yield and water use efficiency. However, the wider scale adoption of aerated SDI has been hampered by fixed & low water air void fraction and nonuniform distribution of air and water flow along the laterals. The emergence of micro/nano-bubble technology provides a good opportunity for its application in aerated SDI because of slow buoyancy characteristics of micro/nano-bubble. This project will be conducted by combined use of theoretical analysis, experimental observation and model simulation. The micro/nano-bubbles will be generated by the coupled system of oxygen concentrators, oxygen diffusion system, and Venturi air injector. Through the study on the two-phrase flow of super-oxygenated water in SDI system, the air and water flow uniformity in the drip irrigation laterals will be examined. Through the combined analysis of different factors in its infiltration, the soil water and oxygen distribution patterns and their transport mechanism in soil will also be evaluated. The characteristics of the root distribution in soil profile, and the transport of water and oxygen in control and aerated SDI will be conducted through pot experiments. The physical model for predicting water and air transport in soil will be made to resolve the mechanism of how aerated SDI enhance the soil aeration, and increase our understanding about the regulation of soil water and oxygen transport in soil. The interrelationship between rhizosphere factors and soil oxygen concentration, soil nutrition, crop growth, physiological response, and water and nutrient use efficiency will be investigated in pot and plot experiments. By coupled use of experimental observation and numerical simulation, a suitable soil aeration index will be found to directly reflect the crop yield, water and nutrient uptake. And the interactionship between soil oxygen transport and soil oxygen consumption, and the response characteristics of soil-crop system will both be unraveled. The comprehensive effect evaluation of soil aeration enhancement on crop yield, crop water and nutrient uptake efficiencyto will be probed, and the possible water air void fraction and dissolved oxygen concentration that brings optimal growth for different crops under different soils will be suggested. In short, all these efforts are aiming at a theoretical understanding of a highly effective regulation on soil aeration and a technical support for aerated SDI.

增氧地下滴灌将水和微气泡混匀后输送到作物根区，能有效提高作物产量和水分利用效率。然而，掺气比率受限、水气传输不均匀是制约其推广的难题。微纳米气泡技术为克服以上难题提供了新的机遇。拟通过试验观测、理论分析与模型模拟相结合的方法，将微纳米气泡技术引入增氧地下滴灌中，研究滴灌毛管水力传输特性；研究掺气比率、溶解氧浓度、土壤质地、滴头流量、灌水定额等因素组合下增氧水入渗特征和土壤湿润体内水气分布规律；通过盆栽试验、辅助染色示踪技术，分析增氧地下滴灌对土壤通气性的改善特征，构建直接反映植物生长和水肥利用的土壤通气性指标；通过小区试验，掌握增氧地下滴灌土壤湿润体内水气动态分布规律，揭示土壤-植物系统对土壤通气性调控的响应机理；结合模型分析，阐明增氧灌溉改善土壤通气性的作用机制；以提高水分和养分利用效率为核心，综合评价土壤通气性改善效应，为土壤通气性的高效调控及效应评价提供技术手段和理论指导。

本研究基于自主设计的增氧地下滴灌系统，通过加强增氧地下滴灌的理论探讨和技术应用，优化现有的增氧地下滴灌技术，突破了掺气比率受限和灌溉水溶解氧较低的局限，实现了增氧地下滴灌条件下掺气比率和溶氧浓度的精量控制。研究了不同压力、活性剂浓度和NaCl介质添加等组合方案下增氧地下滴灌的水气传输特性，明确了增氧地下滴灌水气传输的关键技术参数，为实现水-氧长距离均匀输送提供了依据。通过土柱培养试验，得到了土培条件下灌溉前后土壤溶解氧含量、氧化还原电位等指标的动态变化规律及其相关关系；以紫茄、番茄、冬小麦和辣椒为供试作物，研究增氧地下滴灌对根际土壤溶解氧、氧化还原电位、氧气扩散速率和土壤呼吸的影响，分析了各相关通气性指标与土壤呼吸的耦合关系，明确了增氧地下滴灌条件下土壤通气性的改善机制。研究了增氧曝气滴灌在不同作物和土壤上的应用，明确增氧地下滴灌对作物生长生理、产量、品质和水肥利用的影响，为我国水肥气一体化灌溉提供有力的技术支撑。. 结果表明，本研究设计的增氧地下滴灌系统的出水、出气和溶氧均匀度分别在95%、70%和97%以上，可实现水、氧、气长程均匀传输。增氧地下滴灌可显著改善土壤湿润体的通气性，无作物条件下增氧处理的土壤溶解氧浓度、氧气扩散速率、氧化还原电位和土壤呼吸速率均有显著增强。增氧地下滴灌可显著改善作物根区土壤通气性，增氧地下滴灌下作物根区土壤的溶解氧浓度、氧气扩散速率、氧化还原电位和土壤呼吸较对照均有显著提高，且改善效果可持续84 h。增氧地下滴灌还提高了作物的水肥利用效率，促进了作物的生长，增加了作物的产量，改善了作物的品质。. 本项目成果在《Irrigation Science》、《Waste Management》、《农业工程学报》、《农业机械学报》及《土壤学报》等期刊发表论文16篇，出版《水气耦合高效灌溉理论与技术》专著1部，申请国家发明专利2件，获得河南省科技进步二等奖1项，河南省教育厅科技成果一等奖1项，培养硕士研究生3名。