Abstract:Soil moistures in 0-1000cm soil layers on different growth age alfalfa grasslands in different rainfall areas of the Loess Plateau were measured and soil desiccation effects on alfalfa grasslands were analyzed and compared. Average soil moistures in 0-1000cm soil layers on alfalfa grasslands of semi-humid area, semi-arid area and semi-arid drought prone area were 10.84%, 7.07% and 5.45% respectively，which were obviously lower than local soil stable moisture and soil moisture on natural grassland. Soil water overuse amounts of alfalfa grasslands of the 3 areas were 540.2，641.1mm and 455.0mm, and average speeds of soil desiccation were 61.2mm, 101.9mm and 99.0mm per year separately. Average annual rainfall infiltration depths of alfalfa grasslands on the 3 different rainfall areas were 187.8, 144cm and 173cm separately, and soil moisture of deep soil layers below rainfall infiltration depth remained in a stable desiccated condition. As alfalfa growth aged, soil desiccation intensity strengthened. Soil desiccation intensities was medium desiccated on the 3 years alfalfa grassland, and were serious desiccated and strong desiccated on the 4 years or over alfalfa grasslands. Thickness of desiccated soil layers were 500-760cm on the 3 years alfalfa grasslands and were over 940-1000cm on the 4 years or over alfalfa grasslands. Years required for soil moisture restoration of desiccated soil layers to local soil stable moisture with alfalfa-grain crop rotations on the 3 different rainfall areas were over 6 years, 11 years and 18 years separately.