Effects of Planting Wheat and Forage Grass on Farmland Soil Erosion in Qinwangchuan Irrigated Regions of Northwest China

To explore effects of Triticum aestivum and forage grass(Elymus nutans+Medicago sativa) plantation on soil wind erosion in Qinwangchuan irrigated region, through measuring the coverage, height and above-ground biomass of the vegetation (or crop stubble) and the roughness, humidity, soil moisture content and wind erosion of the soil surface, analysis was done of the vegetation for characteristic indices and of the soil erosion under vegetation. Results show that during the whole wind erosion season, the amount of soil loss was big in late autumn and beginning winter, then became very small in winter, and once again became bigger when spring came, the dynamic cured line of erosion liked "U" shape. The most severe season of wind erosion was from March to May, and the wind erosion from September to October should not be ignored. The coverage, height and above-ground biomass of mixed sowing grass were significantly higher than that of wheat alone (P < 0.05). The order of roughness, humidity and soil moisture of these treatments were mixed bowing grass land > wheat land > bare land, while the order of wind erosion was opposite. Correlation analysis indicates that the coefficients between soil erosion and above-ground biomass was the highest (r=-0.841), followed by vegetation coverage (r=-0.816) and vegetation height (r=-0.726). Regression analysis demonstrates that for every 1 g·m^-2 of increase in biomass, the soil erosion decreased by 6.0 g·m^-2. From analysis of the most severe wind erosion period (March to May), planting spring wheat couldn't prevent soil wind erosion, because the erosion of wheat land was similar to that of bare land, while planting Elymus nutans+Medicago sativa might significantly reduce wind and soil erosion declining rates up to 57%. Obviously, in order to reduce soil erosion in Qinwangchuan irrigated region and improve the ecological environment of Lanzhou New Area, it was necessary to reduce the planting of spring wheat, and vigorously promote the planting of perennial grass (such as Elymus nutans+Medicago sativa).