每年7-9月的夏秋季,是柑桔抽秋梢和果实的迅速膨大时期,需要大量水分。但从降雨量看,此期雨量约占全年的30％以上,降水集中,来势猛、时间短,雨量大,造成大量地表迳流,渗入土中的水分少。再加上天气炎热,温度高,日照强烈,是土壤失墒最严重的阶段,含水量最低。我省川东南地区夏伏旱发生频率高 July and September each summer and autumn, is the citrus pumping autumn tips and fruit rapid expansion period, requires a lot of water. However, from the rainfall, the rainfall in this period accounts for more than 30% of the whole year, and the precipitation is concentrated, the momentum is fierce, the time is short, the rainfall is heavy, resulting in a large amount of surface turbulence and less water infiltration into the soil. Coupled with the hot weather, high temperature, strong sunshine, soil moisture loss is the most serious stage, the lowest moisture content. Summer drought occurred in southeastern Sichuan Province, high frequency of drought