forage species planted by the Grassland Research Institute at a field station in Xilinhot in 1976, shows that only three species—Roegneria turczaninovii, Aneurolepidium chinense, and Elymus sibiricus L.—survived the cold winter and produced a high, stable, aboveground biomass (Wu-yun-gao-wa, 1984). Many wild forage species, although established, have produced low and unstable yields, whereas others have produced high yields but have been unable to survive the extremely cold winter followed by dry spring or summer. In 1978, scientists at the Grassland Research Institute developed a new variety Medicago sativa-falcata, by crossing Medicago sativa (2n = 32) with Medicago falcata L. (2n = 16,32) (Chen, 1984). The new variety has produced a consistently good yield of high-quality forage, demonstrated a survival rate of 92% through winter temperatures as low as –40°C, and adapted well to a variety of environmental conditions.
It is believed that overgrazing has caused a decline in the variety and productivity of palatable species (Chen et al., 1984). Much research has focused on methods for restoring degraded grasslands or establishing artificial grasslands in arid and desert regions. Ma et al. (1989) have studied interseeding as a method for improving degraded steppe and abandoned land. Beginning in 1975, the Grassland Research Institute attempted to establish artificial grasslands in Damao Banner on the Wulanchabu Plateau (Dong et al., 1988). This project included experiments on the selection of regional forage species, timing and methods of sowing, interseeding of legume and grass species, rotation farming systems, and control of insect pests and plant diseases. In the course of nine years, this project resulted in the creation of 807 hectares of artificial grassland.
Research of this type increased in late 1970s, although fundamental problems have persisted: Results obtained in one region have not been applicable in other regions where environmental conditions differ. Different studies have used different experimental protocols. Poor control of seed exchange and use of unlabeled or incorrectly labeled seeds have been common in some remote areas (Chen and Wu, 1988).
In 1978 the Grassland Research Institute began controlled experiments to test the performance of 39 common forage species under different conditions. These experiments were conducted at 25 sites in 13 provinces or autonomous regions, from Tibet in the southwest to Heilongjiang in the northeast. The experimental sites were selected to cover a wide range of environmental conditions: latitudes from 26°36'N to 40°56'N and longitudes from 91°61'E to 124°48'E; elevations from 148 to 421 m; annual mean temperatures from –2.4 to 15°C; maximum temperatures from 19.2 to 40.2°C; minimum temperatures from –40 to –42°C; annual precipitation from 200 to 1300 mm; soils