干旱沙漠地区小麦田土壤水分变化的数值模拟

利用SWAP模拟程序模拟沙漠地区小麦土壤水势变化、水分利用的结果,无论是灌淤土,还是流动沙丘沙土,即使是在最低灌溉标准(土壤水分含量保持田间持水量的40%),小麦作物仍不受干旱威胁。由于每次灌溉水量偏大,以及土壤的高渗水特性,流动沙丘风沙土深层渗漏损失率高达60%~90%,而灌淤土也达30%~70%,这种损失随灌溉量增加而增加,这表明在这一地区将灌溉量降到目前的最低标准(6 490 m³·hm^-2)以下是值得考虑的。实验区土壤养分含量较低,且施肥改良土壤水肥保持能力的效果不能立即表现,在目前的施肥标准下,施肥量对土壤水势、以及水分利用率没有显著影响。流动沙丘沙土的灌溉量远高于灌淤土,但根系区土壤水势平均值、最低值均相对较高,特别是最低值是灌淤土的2~3倍。相比两种土壤,除在表土层、根系层土壤水势有明显差异之外,临界层以下土层并无显著差异。

Simulation of the Change of Soil Water of Wheat Field in Arid Desert Area

This paper presents the simulation results of soil water of wheat field by SWAP. The average and highest values of soil water potential decrease as the increase of the amount of irrigation, and they were much lower than the water potential at which the growth of crop was prohibited. Whether in clay sandy soil formatted by irrigation with Yellow River water, or in desert sandy soil, wheat was not threatened by drought while the soil moisture was kept in 40% of field capacity. Because of the large amount of irrigation and bad water holding capacity, irrigating water infiltrated downward deep soil layer by 60%~90% in which crop could not uptake the soil water. The infiltrating amount was increased as the increase of irrigating amount. Therefore, in arid desert area, the irrigating standard could be reduced to lower than 6 490 m 35hm {-2} with surface irrigating method. Due to low soil fertility, the increase of fertilizing amount with organic matter and chemical fertilizers could hardly lower soil water potential, and enhance the use rate of water. The soil water potential changed very significantly in the soil layer at 0~40 cm deep, but it did not change underneath 40 cm of soil layer.