Dynamics of biomass and nutrition of mixedsown pasture atblack soil beach in Yellow River headwater area

It is an important way to transfer degraded natural grassland into artificial one, for example the extremely degraded grassland at black soil beach in the Yellow River headwater area. The dynamic of productivity and nutritional value in mixedsown Elymus nutans, Festuca sinensis, Puccinellia distans, Poa crymophilia and Leymus secalinu were studied, and effects of grazing on the forage production were analyzed. The results showed that 34.9% of productivity, 144.3 g/m2, was lost naturally from August to the next year April, in which 187.2 g/m2 was fed by livestock. In fact, utilization rate of the grassland was 45.2% in traditional grazing way. Nutrition value of forage decreased generally in whole cold season, i.e, 69.86% of crude protein and 65.85% of crude fat decreased. So, the grassland belongs to the CN nutritive type in summer and C type in winter. In the case, the grassland would be used by mowing during the growing season in summer and grazing in a moderate intensity in winter.