It indicated in this paper the main type

distribution

producti-veness of grazed natural grassland and avenue to improve and use ration-ally it inZhifang Valley

Ansai County

With reclaiming and over stoc-king

natural grassland distributed mainly on steep gully side

making up 28

8%of the total land area

- and its yield capacity was generally 1.800-2.550 kg/ha (fresh weight)。After closure against grazing for 2}3 years or interseeding Caragana korshinskii and Sophora viciifolia and so on

the yield capacity increased 1.9-}-2

1 times and tire rate of low一grade herbage decreased to 7.9-rll。1%from 40

9-76

9. Authors suggest that combiningestablishment of artificial grassland with transforming crop rotation sys-tem and animal production Could promote agriculture and animal husban- dry in the loess hilly and valley region