长期免耕一膜多用下土壤水力特征与作物根系吸水机制研究

Prevention of the plastic residual pollution is one of the most important issues for the sustainable development of the dryland agriculture in China, and a kind of plastic mulching technology-‘one film for multiple years’ under no-tillage (PMm-NT) is proposed as an measure to prevent the plastic residual pollution. Although PMm-NT can effectively control the plastic residual pollution, with the increase the application year, it may change the soil structure, soil hydraulic properties, and root development, and then influence the root water uptake. Such effects have still not been evaluated, and they are important for the full understanding of the sustainability of PMm-NT. In this project, based on long-term PMm-NT experiment, and with the application of Electrical Resistivity Tomography tecnology and the combination of field measurement and simulation, such an important issue will be analyzed. Related work in this project will include: (i) measurement of the soil aggregate, pores structure and soil hydraulic parameters in long-term PMm-NT experiment; (ii) quantification of the 2D root distribution, spatio-temproal dynamic of soil water and root water uptake; (iii) development of simulation methods for root water uptake in long-term PMm-NT, recognizing the contribution of soil hydraulic parameters and root distribution parameters to the change of root water uptake, and locating the key parameters. Those work will provide important and necessary reference for the development of sustainable plastic mulching technology in the dryland of China.

残膜污染防控是我国农业绿色发展中的重要命题，免耕一膜多用是当前通过农艺手段进行残膜污染防控的重要措施。免耕一膜多用的长期应用是否会因土壤紧实程度加深而影响土壤水分运移能力，限制根系发育，降低作物根系吸水尚未可知，是可持续地膜覆盖模式构建中面临的重要实际问题。如何克服根-土界面的不可视性，获取高分辨率土壤水分运移和根系吸水信息是该方面研究的难点问题。本项目拟基于免耕一膜多用定位试验平台，采用高密度电阻层析成像技术和数值模拟与解析等技术方法手段，查明长期免耕一膜多用下的土壤水力特征变化机制，揭示作物根系生长、土壤水分二维运移、作物根系吸水对长期免耕一膜多用的响应机理，定量解析土壤水力学参数和根系空间分布对不同覆膜方式间根系吸水量差异的贡献。通过三方面的系统研究，定量阐明长期免耕一膜多用对作物根系吸水的影响机制，为可持续地膜覆盖模式构建提供重要理论支撑。

免耕一膜多用是残膜污染防控的新型技术模式，但该技术模式长期应用是否会因土壤紧实程度加深而影响土壤水分运移，限制根系发育、进而影响根系吸水尚未可知，是其规模化推广应用中亟需解决的科学问题。围绕这一科学问题，本项目利用免耕一膜多用长期定位试验平台，开展了长期免耕一膜多用下作物根系吸水影响机理的相关研究，得到以下主要结果：（1）免耕一膜两用可在地膜减量情况下取得与常规覆膜种植相似的产量水平，采用免耕一膜两用较裸地栽培在旱地农业生态系统中使得有限降水更大程度为作物吸收，继而取得与常规覆膜相似的产量和节水效应；（2）免耕一膜两用引起土壤容重增加，但提高了土壤中大团聚体和小孔隙占比以及土壤保水能力，引起了土壤水力学参数变化，但土壤水力学参数变化对根系吸水量影响有限，同时免耕一膜两用对各土层根长密度和根系二维分布影响不显著，采用高强耐候地膜有效避免了第一年生育期结束时地膜破损对次年增温保墒效应的影响，因此免耕一膜两用可取得与常规覆膜栽培相似的根系吸水促进作用。本项目研究结果表明，免耕一膜多用中免耕和地膜减量不会阻碍旱地天然降水向作物体水转化，采用免耕一膜两用可同步实现地膜污染防控和作物水分利用效率提升。