Effects of different alfalfa-crop rotation patterns on water recovery of degradation alfalfa grassland

Experiments were carried out in the drought areas of southern Ningxia Hui Autonomous Region on the loess plateau during from 2003 to 2005, in which three kinds of crops including spring wheat, potato and millet were rotated in the form of combination on the 10-year-old degraded alfalfa grassland. The purposes are to study and compare the soil moisture restoration conditions and crop production effectiveness between different rotations, thus approach more reasonable alfalfa rotation patterns. The results showed that, rotation in 0-60 cm soil layer was vulnerable to the impact of precipitation and surface evaporation, moisture in 60-120 cm soil was mainly consumed by rotation crops, while moisture in 120-200 cm was stable relatively and rarely influenced by precipitation and surface evaporation, and there was a trend of continuous restoration in it with the increasing of rotation year. The moisture in 120-200 cm soil could be improved by alfalfa-crop rotation. And it was significantly higher than that of abandoned land and grassland (CK), and could obtain certain crop yields meanwhile. Compared with other alfalfa-crop rotation patterns, potato- potato- wheat rotation pattern (PPW) has better restoration role on grassland moisture and ability to make use of limited precipitation. Total yields and water use efficiency (WUE) of rotation crops with PPW pattern were both relatively higher than others, i.e., 5214.5 kg/hm2 and 9.38 kg/(hm2·mm), respectively. Compared with alfalfa farmland before crop rotation, the net moisture recovery amount of PPW rotation pattern was 24.73 mm in 120-200 cm soil layer.