石羊河流域膜下滴灌土壤水盐空间分布特征

Spatial distribution features of soil water and salt with drip irrigation under mulch in Shiyanghe Basin

通过田间试验,研究了膜下滴灌条件下,不同灌溉定额对春玉米生育期土壤水盐空间分布特征的影响.结果表明土壤含水量的时空分布受灌溉水量的影响.在灌溉期,0~20 cm土层土壤水分含量明显增加.随灌水定额的增加,土壤脱盐深度呈增大的趋势,其中,0~20 cm土层土壤脱盐现象明显,40~100 cm土层土壤积盐现象明显.在春玉米生育后期,灌水定额对滴灌带间的土壤淋洗作用较前期明显.在非灌溉期,由于较强烈的蒸发蒸腾作用,土壤含水量持续降低,作物的主要根系吸水层0~60 cm土层土壤水分含量阶段性变化明显.土壤盐分随土壤水分向上运移,在0~40 cm土层发生积盐现象,40~100 cm土层发生脱盐现象,畦灌方式在0~100 cm土层内均发生脱盐现象.膜下滴灌条件下,春玉米在拔节期前0~100 cm土层土壤含水率和含盐率变异系数分别属于中等变异和弱变异强度,之后两者均属于中等变异强度,且土壤含盐率变异强度始终低于土壤含水率.

Field experiments are conducted with drip irrigation under mulch in spring maize growth pe- riod to identify spatial distribution features of soil water and salt. The results show that the soil moisture content time - space distribution was influenced by irrigation quota. In irrigation period, the soil mois- ture content in 0 -20 cm layer increases significantly. The desalination layer depth increases with in- creasing irrigation quota. The obvious desalination occurs in 0 -20 cm layer, while soil salt accumu- lates in 40 - 100 cm thick layer. The salt-leaching is better in the horizontal direction than that in the vertical direction, further the salt-leaching is better along the direction from one emitter to another than along the direction from one drip irrigation belt to another belt. In no-irrigation period, soil moisture obviously decreases in 0 -60 cm layer because soil water declines continuously caused from a strong evapotranspiration. The soil migrates with water from a deep soil layer to a shallow one. Soil salifica- tion occurs in 0 -40 cm layer and soil desalination emerges in 40 - 100 cm layer. However, the desal- ination develops in whole 0 - 100 cm layer in border irrigation schedule. The coefficients of variation of soil water and salt are in moderate and low intensity before the jointing stage. Since then, the coeffi- cients of soil water content and salt content are all in moderate intensity after that stage, but the coeffi- cient of variation of soil salt content is lower than that of soil water.