黄土高原旱坡地的降水分配大致如下：地表流量＜５％～１０％；地面蒸发量４５％～５０％左右；植物蒸腾量，４５％～５０％。旱坡地的水土保持不应仅考虑地表径流的入渗拦蓄，更应重视减少地面蒸发。“地面覆盖十生物蓠”旱坡地生态农业系统可以有效减少地面蒸发，控制水土流失，大幅度提高作物产量，投入少、见效快、适宜大面积推广。 The distribution of precipitation on the dryland in the Loess Plateau is roughly as follows: surface flow <5% ~ 10%, ground evaporation 45% ~ 50%, and plant transpiration 45% ~ 50%. Water and soil conservation in dryland should not only consider the infiltration and retention of surface runoff, but should also pay more attention to reducing ground evaporation. The ecological agro-system on the sloping land can effectively reduce ground evaporation, control soil erosion and greatly increase crop yield with less investment and quick response. It is suitable for large-scale popularization.