河套灌区暗管排水下水-盐-氮运移特征及灌溉-施肥-排水调控机制研究

Subsurface pipe drainage technology which used for Salinization prevention and control is always regarded as an essential tool in typical salinization Hetao irrigation area. The theory of traditional farmland water irrigation and leaching to keep the balance of soil salt under the water-saving conditions is impacted. The purpose of this project is to study how to improve the efficiency of water and fertilizer use and the rate of soil desalination under the condition of concealed drainage. The experiment was conducted to several treatment groups according to different optimal space and depth of buried tube and different irrigation and manure level. The effect of crop growth, Soil water, nitrogen, salt distribution and accumulation of different treatments will be analyzed through fixed point measurements and sensors and clarified its influence on the displacement of underground pipes, the amount of salt discharged and the amount of nitrogen and phosphorus loss. The reasonable arrangement of pipe and irrigation and fertilization modes aim at high salt rejection , high utilization efficiency of water and fertilizer, and low nitrogen and phosphorus loss rate should be proposed. Considering the DRAINMOD model and crop growth model(EPIC) in model updating, a reasonable zoning Water - fertilizer - salt control technology mode is proposed that providing theoretical basis and technical support for the large-scale underground pipe drainage, the prevention and control of salinization and the efficient utilization of water and fertilizer in Hetao Irrigation District in the future.

河套灌区是典型的盐渍化灌区，暗管排水是盐渍化防控的重要手段。本项目针对节水条件下，传统的农田水利灌溉淋洗保持土壤盐分平衡的理论受到冲击，在暗管排水下如何提高水肥利用效率与土壤脱盐率等问题开展研究。设置不同暗管间距与埋深以及不同灌溉施肥定额小区试验，基于定位取样和传感器连续采样相结合分析不同暗管布置和灌溉施肥模式对作物生长、土壤水-氮-盐分布和累积的影响，明确其对暗管排水量、排盐量、氮磷流失量的影响，以脱盐率高、水肥利用效率高、氮磷流失率低为目标，提出合理的暗管布置及灌溉施肥模式。针对浅地下水地区考虑地下水补给过程修正DRAINMOD模型，并结合EPIC作物生长模型，耦合建立DRAINMOD-EPIC模型并进行不同情景模拟，提出不同土质、不同地下水埋深地区节水-减肥-控盐技术模式，形成不同地下水地区合理的灌溉-施肥-排水技术模式，为河套灌区暗管排水、盐渍化防治及水肥高效利用等提供理论依据。

本项目在农田节水的基础上，结合田间暗管排水条件下的土壤水盐氮分布、排水排盐效果、作物生长情况等，分析描述暗管布置下的作物水肥耦合效应与水肥盐运移特征，基于水-盐-氮监测数据进行模型的验证与耦合，对不同暗管布置参数、不同水肥制度以及不同地下水位等情景下的水盐氮运移、作物生长等指标进行定量研究。针对轻度盐碱化土壤的土壤盐分控制及次生盐渍化防治，以向日葵为研究对象，设置不同梯度纯氮施用量及灌水量，在各个生育期采集土样，测试植株生育指标。分析不同组合模式对土壤、地下水中氮、盐等水土环境及作物生长、产量、品质的影响，通过不同指标确定最优水肥组合及控释肥施用量。基于传感器技术定量连续监测不同处理排水量、排盐量、排氮量，估算土壤中盐分、氮素等溶质的累积量和损失量。优化出了能够提高作物品质的暗管耕地和轻度盐碱地优质食葵水肥技术，提高了作物的肥料利用效率，减少了氮肥地下水淋溶量。针对内蒙古河套灌区中、下游中度和重度盐碱化土壤，将暗管排水排盐技术与物理改良、化学改良和生物改良技术相结合，施用土壤改良剂和土壤深耕深松，通过暗管排水技术要素优化及农田生态水土环境预测、暗管排水条件下水盐运移规律与排盐效果监测、暗管排水条件下灌区面源污染控制和灌区排盐对容泄区影响的研究，明晰了水盐运移规律，确定了针对于河套灌区中重度盐碱地改良的最佳暗管布设。深入了解了暗管排水方式对“土壤-作物-环境”系统的响应规律，达到了最佳的水分和养分供应与盐分的控制效果，减少环境污染的同时提高水分利用效率，提高肥料偏生产力。项目的实施确定了科学合理的排水排盐暗管技术指标，结合作物生长过程提出优化灌溉-施肥-排水模式，改善了土壤结构，为实现河套灌区不同区域盐渍化防治、面源污染防控、水肥高效利用以及暗管排水大规模铺设提供理论依据。