浓度衰减条件下养分溶液点源入渗机理及滴灌压差施肥运行参数的优化

To the drip irrigation method，the pressure differential fertilization is the most common fertigation way at present.And during its fertilization process，the nutrient solution concentration decreases constantly，which is a remarkable characteristic of this fertigation way.However，currently there is few research on this point source infiltration problem in condition that concentration decreases constantly，meanwhile，the study on the pressure differential fertilization is not systematic. On this background，this research program will be carried out surrounding the pressure differential fertilization closely and will be from two aspects，namely，the point source infiltration，and the operation and management.In detail，a point source infiltration test will be done in order to study the point source infiltration mechanism in the condition that concentration decreases constantly，and a hydraulic performance test of the pressure differential tank will be made in order to study the decreasing course of the nutrient solution concentration in the tank.Based on these mechanism research，a field experiment will be carried out in order to determine a reasonable running model of the pressure differential fertilization and establish the operating rule of the pressure differential tank.Through these tests，we expect to solve these problems，namely，"what is the point source infiltration law of the nutrient solution whose concentration decreases constantly？and compared with previous study，the differences would be what？when the solid fertilizer was used in fertigation，what is the nutrient solution concentration decreasing law？How could we choose a reasonable running model in order to guarantee the effective utilization of fertilizer in the pressure differential fertilization？".This research would enrich and develop the point source infiltration theory and would offer a technological support to the pressure differential fertilization in drip irrigation.

滴灌压差施肥是目前最常用的灌溉施肥方式，在施肥过程中养分溶液具有浓度不断衰减的特征。然而目前针对浓度衰减条件下养分点源入渗机理的研究较少，对滴灌压差施肥的研究也不系统。在此背景下，本项目紧紧围绕压差施肥，从点源入渗机理和运行参数优化2个方面展开研究，通过点源入渗试验和hydrus模拟的手段研究浓度衰减条件下养分溶液点源入渗机理；通过田间试验研究优化滴灌压差施肥运行参数，进一步制定压差式施肥器的操作规程。以期解决："浓度衰减条件下养分溶液点源入渗规律是什么，与以往浓度不变的研究成果有何不同？如何通过合理的运行调控，以保证压差施肥肥料的有效利用？"等科学问题，项目的开展可丰富和发展点源入渗基础理论，为滴灌压差施肥的进一步推广应用提供技术支撑。

为提高水肥资源利用效率，我国正在加快实施水肥一体化技术。压差施肥罐是我国最常用的微灌施肥装置，施肥时罐内肥料溶液浓度不断衰减是其主要特征。这种水力特征如何描述，其土壤水肥如何分布，进而如何实现微灌施肥运行过程的优化控制，针对这些问题，展开研究：（1）设置了300、600和900mg/L三个不同初始浓度，并设置了20和50min不同衰减时间，展开了点源入渗试验，分析了不同浓度衰减条件下水肥分布特征，初步结论认为不同浓度衰减过程对水分分布影响不大，但对肥料分布有一定影响，研究丰富和发展了点源入渗理论；（2）围绕压差施肥罐水力特征、运行过程优化展开研究，①引入CFD模拟方法，对9.42L施肥罐模型，设置进口流量1.425和0.71m3/h，分析浓度衰减规律，结果显示模拟的衰减过程与理论公式基本一致，而施肥结束时间与经验公式偏差3%左右，认为CFD技术可用于描述这一衰减过程，这为研究压差施肥罐的水力性能和结构优化提供了一种新的思路；②开展了微灌压差施肥运行过程自动控制研究，设计了一种轻小型半自动滴灌压差施肥车，并给出了使用方法，可用于可溶性肥料；进一步，针对生产上仍较多使用固体肥料的现象，又构建了一种自动控制压差施肥系统，适用于施用固体肥料。该研究形成的知识产权为解决压差施肥运行过程的自动控制提供了一定的技术指导，也为解决微灌施肥实际生产问题提供了一套解决方案和装置；③通过试验，设置施肥罐入口流量0.6和0.9m3/h，微灌管网入口压力0.06、0.10、0.14MPa，分析了施肥罐和微灌管网不同运行模式下灌水器的水肥分布，认为肥料分布均匀性小于水分分布，应在灌溉设计中考虑施肥均匀性；④使用压差施肥对大田覆膜小西瓜进行了不同滴灌频率生长特性研究，认为在果实膨大期中频、果实成熟期低频此灌溉组合下处理效果较好，研究可为豫北平原地区大田膜下滴灌小西瓜灌溉施肥的运行提供一定指导。