西辽河平原灌区玉米浅埋滴灌土壤次生盐渍化机制及调控

Xiliaohe Plain is a few irrigated maize areas located in the world maize production "gold belt” in our country. Maize is the dominant plant and extensive and high yield per unit area. In the context of dry warming trend, the contradiction between continuous high yield and stable yield of maize and sustainable utilization of water resources is increasingly outstanding. Shallow subsurface drip irrigation is the main technology of agricultural new water-saving irrigation, and application area is continuously increased in this area. Due to thermal resources are sufficient, the vast evaporation of soil which causes light and medium saline-alkali land in the Xiliaohe Plain. Under shallow subsurface drip irrigation, the risk of soil secondary salinization will increase. In this study, the control treatment (CK) were mulched drip irrigation and flood irrigation, soil water and salt migration rule and the producing process of soil secondary salinization were studied in nonsaline alkali soils and saline alkali soils. To explore regulation effects on soil water and salt migration irrigation in growth period and supplemental irrigation in non- growth period. To reveal the mechanism of soil secondary salinization and to determine regulation pathways under shallow subsurface drip irrigation, to propose irrigation system of the efficient use of water and security of environment. It is important for the sustainable land utilization and agricultural sustainable development for Xiliaohe Plain and similar areas.

西辽河平原地处世界玉米生产“黄金带”，是我国为数不多的井灌玉米区，玉米作为优势作物，种植面积大，单产水平高，但在气候干暖化的背景下，玉米持续高产、稳产与水资源的持续利用矛盾日渐突出。浅埋滴灌作为农业新的节水灌溉主推技术，在该地区推广应用面积持续增加。西辽河平原地区由于热量充足，土壤蒸发强烈，耕地中轻、中度盐碱地面积所占比例高，而在浅埋滴灌条件下，土壤次生盐渍化发生风险将会进一步增加。因此，本研究拟在非盐碱和轻度盐碱两种土壤类型上，以常规漫灌和膜下滴灌为对照，研究浅埋滴灌条件下土壤水盐运移规律和土壤次生盐渍化的发生过程，探索生育期内灌溉和非生育期补灌对土壤水盐运移的调控效应，以期揭示玉米浅埋滴灌土壤次生盐渍化形成机制，明确玉米浅埋滴灌土壤次生盐渍化的调控途径，提出玉米浅埋滴灌高效用水且环境安全的灌溉制度，对于实现西辽河平原及同类地区耕地资源的可持续利用和农业可持续发展具有重要意义。

2019年1月至2022年12月，在内蒙古通辽市现代农业科技园区盐碱地，实施了不同灌溉方式试验、玉米浅埋滴灌条件下灌溉定额试验、玉米浅埋滴灌条件下秸秆二次粉碎深翻还田试验，研究了玉米浅埋滴灌土壤次生盐渍化机制及调控途径。浅埋滴灌较膜下滴灌具有较高的有效穗数,玉米花后维持较高的物质生产能力和转运效率，增强了弱势粒的灌浆速率；玉米根系SOD、POD酶活性高，生育后期保持了较强的活力，是其高产高效重要的生理基础。浅埋滴灌容易造成土壤盐分在表层聚集，0—10cm、10—20cm土层土壤积盐率达到6.27%—8.77%、9.86%—14.45%；拔节期，0—10cm土层土壤盐分含量与土壤温度呈极显著正相关，与土壤水分呈负相关；浅埋滴灌条件下土壤盐分会以滴头为中心向四周呈现“放射状”路径运移，处在中轴位置的盐分由于水量充足运移较深，而距离中轴越远水量越少，盐分运移也会逐渐变浅，在土体中形成近椭圆形的“盐壳”，灌溉定额越大积盐半径越大；在棵间蒸发的作用下，下层盐分仍会垂直上移至地表聚集，距离滴头越远盐分分布越浅，越容易上升至地表积盐，从而造成表层土壤盐分距离滴头越远盐分含量越高的特点。浅埋滴灌秸秆还田条件下，30cm土层处盐分含量明显降低，随着土层的加深土壤盐分含量逐渐升高；土层的加深使地表蒸散作用逐渐减弱，且翻耕在土壤深层形成较大孔隙、还田秸秆形成了“夹层”，土壤盐分较难再重新上移至地表聚集，这对于浅埋滴灌条件下土壤次生盐渍化的防控具有积极意义。本研究揭示了浅埋滴灌条件下玉米高产高效的生理机制，探明了浅埋滴灌条件下土壤盐分运移分布规律及对灌溉定额的响应，揭示了土壤次生盐渍化的机制，探索了土壤次生盐渍化的防控途径。可为构建西辽河平原及同类地区玉米浅埋滴灌高效用水且环境安全的技术体系提供科学依据及实践指导。