Hilly areas in arid land of Qinghai Province are mainly distributed in the section of Longyangxia to Shigouxia of _ the trunk streams of the Yellow River valley east of the Riyue Mountains as well as low-middle hills on both banks of the Huangshuihe valley, the main tributary of the Yellow River. They cover a total area of 12,446.8 sq. km with elevations ranging 2000-2800rn. Of the 3,531,500 mu (15 mu equals to 1 ha), ^ of cultivated land, irrigated fields occupy 359,000mu, and dry hilly land (mostly sloping land) approximates 3,180,600mu. The study area is dry with scarce precipitation and deficient water resources. Soil erosion is serious and natural disasters (hailstones, drought, debris flows, etc.) frequently occur. However, thanks to the thick soil layers and favorable temperature, light and heat conditions, spring wheat, qingke barley, pea, oil rapes and potatoes are suitable to grow here where natural precipitation is dependable for crops. It is a typical rainfed agricultural area which possesses the following Cxharacteristics .
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