The location experiments have been carried out to study soil moisture balance of farmland under different rota-tion systems in loess hilly areas of South Ningxia。The results show that the rotation between grain and bean (i. e.

spring pea - spring wheat-spring wheat-broom corn millet )could adjust soil moisture and maintain the soilmoisture in basic balance within the rotation 's period;alfalfa can be taken as a part in the rotation of grass-crop。The soil moisture in layer of 1 m is adaptative to plant drought -resistance crops

such as millet

after the alfalfagrows 5-6 years;the soil moisture in layer of 2 m can be repenlished after the drought-resistance crops wereplanted for 2-3 years。The long-term continuous cropping of spring wheat can lead to the decreasing of soil fer-tility

the extending of pest and diseases

the breeding of weeds and the reducing of productivity

but can not causeheavy problem for soil moisture。