华中丘陵红壤的水分问题　Ⅳ.桔园红壤的水分状况

WATER PROBLEMS OF RED SOIL IN HILLY REGION OF CENTRAL CHINA Ⅳ.THE WATER REGIME OF RED SOIL IN ORANGE ORCHARD

1990—1993年在江西省第四纪红色粘土发育的红壤并掺有第三纪红砂岩风化体的桔园红壤进行了水分性质和水分状况的研究。结果表明，由于桔园红壤中粘粒含量比附近的典型粘质红壤中低，－15MPa土水势时的土壤含水量较低，相应就提高了桔园红壤中的有效含水量。还发现，一年中桔园红壤0—100cm土体内的贮水量较低，即使在丰雨的上半年，土体中也出现低于有效水的含水量范围，这可能与柑桔生长的耗水较大和心上层的土壤容重较大等因素有关。但在100cm以下土层中全年的贮水量都较丰富。桔园红壤0—100cm土体内，不论在上半年或在下半年，其Wfc值均小于1，反映了其贮水库容中尚存在较大的空间可继续蓄水。

This paper deals with a study on the water characteristics and water regime of redsoil derived from Quaternary red clay mixed with the weathering material of Tertiarysand stone in an orange orchard of Jiangxi Province. Results showed that the availablewater content of the soil was higher due to lower clay content in the soil layer ascompared with that of the surrounding typical clayey red soil. The water regime ofred. soil in orange orchard reflected that water content of 0-100cm layer of the soilwas usually lower than the range of available water content even in the first half of ayear. It might be related with large consumption of soil water by the growth oforange trees and the high bulk density of subsoil of the soil. However, the waterstorage beneath 100cm soil layer was still richer either in the first half of a year orin the second half one. Results also showed that the value of Wfc. in 0-100cm layerof the red soil in orange orchard was lower than I throughout a year, which meantthat a higher amount of empty waterstoring capacity at that layer where can acceptcontinuously the hanfall could be found. Moreover the W fo beneath 100cm of thatsoil was more than l, reflecting a richer water storage at the soil layer of beneath100cm in the second half of a year with severe shortage of rainfall. Consequently, toincrease the acceptance of rainfall in the first half of a year and to use the richerwater storage in deep soil layers in the second half of a year are of imPortantsignificance for alleviating the draught in summer and autumn and raising the useefficiency of water resource in red soils.