Simulation of sustainable use of soil water in dry land for alfalfa-grain rotation system at Changwu arid-plateau of China

In order to find out a grain-crop system for sustainable usage of soil water, effects of different alfalfa-grain rotation systems on soil water restoration were simulated and investigated, based on long-term experiment at Changwu arid-plateau, by combining on-spot investigation and computer simulation methods. Validation results showed that correlation coefficient between simulated and observed values of soil water storage in 0-2m soil for alfalfa-grain rotation system (4-years-old-alfalfa, potato, winter-wheat, winter-wheat and winter-wheat) was 0.97(a<0.01). The correlation coefficient between simulated and observed value of soil moisture in 0-5m soil for alfalfa land, winter-wheat field and potato field was 0.94(a<0.01), 0.93(a<0.01) and 0.87(a<0.01) respectively. Simulation results showed that the cultivation of potato and broomcorn millet was benefit to recover soil desiccation. When spring maize or winter wheat cultivated, soil water varied with soil desiccation grade. When soil desiccation grade was serious, soil water restored slowly; when soil desiccation was slight, soil water reduced. Grain crop rotation system with annual sequence of potato, broomcorn millet, spring maize, potato, broomcorn millet and winter wheat was benefit to restore soil water after alfalfa plantation. At Changwu arid-plateau, alfalfa could be replanted after its cultivation years reached to 9-12 years.