Water Restoration of Dry Soil Layers in the Loess Plateau and Crop Yield Response

Field experiment was carried out to study dry soil layers of alfalfa grassland water restoration and crop yield response in water restoration.Five treatments were established in the experiment,alfalfa→ millet →spring wheat →potato →pea(WPPe);alfalfa →millet →corn →corn →spring wheat(CCW);alfalfa →millet →potato →spring wheat →corn(PWC);alfalfa →millet →fallow →pea →potato(FPeP);conventional farming system(CS).The results showed that when the ratio of soil water content in field after alfalfa to soil water content at crop lower limit for growth denoted water restoration,the ratio increased in normal rainfalls and decreased with little rainfalls.When the ratio of soil water content in field after alfalfa to soil water content in CS denoted water restoration,the ratio increased continually and was influenced little by rainfalls.After four years,soil water content of WPPe,CCW,PWC,FPeP in 0～500 cm soil depth which had only 63.66% of CS in April 2001 had reached 90.51%,89.83%,92.17%,96.72% of CS in October 2004 respectively.Crop yields in field after alfalfa had no significant different with CS.However,water use efficiencies in field after alfalfa were significantly higher than in CS.Potato and corn which harvest in autumn were optimal for rotation in field after alfalfa.