灌溉水中盐分对土壤结构性质及水流运动特征的影响

再生水和微咸水等用于农田灌溉对缓解农业用水紧缺、保证粮食稳产高产方面作用显著。但这些非常规灌溉水中的盐分进入受灌农田土壤会引起土壤结构性质的改变,进而引起入渗水流运动特征的变化,增大了农业灌水和施肥的管理难度及地下水受污染的风险。本文通过室内灌水入渗试验,研究了灌溉水盐分浓度(0、1.0、3.0和5.0 g/L)、灌水频率(1天1次、2天1次、4天1次)、含盐灌溉水-清水交替灌溉模式(纯清水灌溉、纯含盐灌溉水灌溉、含盐灌溉水-清水交替灌溉)对受灌土壤容重、团聚体结构稳定性、孔隙结构特征、地表入渗性能以及入渗水流运动非均匀特征的影响。结果表明,适度的盐分浓度、较低的灌水频率但较大的灌水定额、含盐灌溉水-清水交替灌溉均有利于提升土壤团聚体的稳定性、抑制土壤板结、改善受灌土壤的地表入渗性能、降低入渗水流运动的非均匀性。研究成果对再生水和微咸水农田灌溉制度设计具有参考价值。

Effects of salt in irrigation water on soil structural properties and water flow characteristics

Non-conventional irrigation water (e.g.reclaimed water and brackish water) for irrigation allevi-ates the shortage of agricultural water resources and increases the crop yield.However,salt in irrigation wa-ter modifies the irrigated soil structure and properties and changes the soil water flow characteristics,in-creasing the difficulty of irrigation and fertilization management and enhancing the contamination risk for groundwater system.In this research,laboratory irrigation experiments carried on manually filled soil col-umns were conducted to study the effects of salinity of irrigation water (i.e.0,1.0,3.0 and 5.0g/L),irri-gation frequency (irrigated every day,once every two days,and once every four days),and saline water and freshwater alternative irrigation schedule (irrigated with freshwater only,irrigated with saline water on-ly,and irrigated with saline water and freshwater alternatively) on soil bulk density,soil aggregate stabili-ty,soil porosity and pore-size distributions,soil surface infiltrability and soil water flow heterogeneity.The results illustrated that,moderate salinity of irrigation water,lower irrigation frequency with higher irrigation quota,and saline water and freshwater alternative irrigation schedule all enhanced the soil aggregate stabili-ty when wetting,prevented soil clogging,improved soil surface infiltrability,and decreased soil water flow heterogeneity.This research has certain reference value for reclaimed and brackish water irrigation schedul-ing design.