Wind tunnels test on anti-wind erosion effect of conservation tillage farmland and caragana collocated with grassland in strip

Abstract: In order to analyze the anti-wind erosion mechanism and anti-wind erosion effect of the protective tillage farmland and the strip arrangement of Caragana to restore deteriorated grassland, the mobile erosion wind tunnel and related supporting equipment are used to conduct the field in-situ test of wind tunnel of the protective tillage, the traditional dry farmland, the degraded grassland, and the grassland with the strip arrangement of Caragana in the cold and dry area of Ulanqab, Inner Mongolia. In the test, the wind speed profiles near surface, sediment transport fluxes and wind sand flow structure are studied, and the windbreaks of farmland and Caragana korshinskii in grassland are analyzed and compared. The results show that the wind speed from the protective tillage farmland and the grassland with Caragana banded configuration of 30 cm height is significantly lower than their corresponding traditional tillage farmland and degraded grassland in the same wind speed of wind tunnel center. And the corresponding sediment transport flux also decreases. The sand flux of the protective tillage and strip-shaped arrangement of Caragana to restore grassland presents a C-shaped distribution with the changes in surface height, which is different from the rapid exponential decline in the sand flux of traditional farmland and degraded grassland with the increase of surface height. In the same wind speed of wind tunnel center, the wind speed of the restoration belt of Caragana is higher than that of the corresponding protective tillage farmland at the same height above the ground surface. Then the largest sediment transport flux of the grassland with Caragana belt appears at the height of 30 cm above the ground surface, and the maximum sediment transport flux occurs at 25 cm above the ground surface for the protective tillage farmland. The anti-wind erosion mechanism of conservation tillage farmland and Caragana microphylla grassland mainly is that the vertical stubble of the protective tillage farmland and the Caragana belt of the degraded grassland can block, decompose and evacuate the wind speed near the surface, so that the wind speed near the ground surface is weakened in different degrees. When the wind speed of the wind tunnel is 11 m/s, compared with the traditional tillage, the protective tillage has a wind speed reduction rate of 86.44% at 50 mm above the surface, while the grassland with the strip arrangement of Caragana has a wind speed reduction rate of 70.69% compared with the degraded grassland. The reduction of wind speed near the ground surface is the fundamental cause of the effective prevention and control of soil wind erosion in the farmland with protective tillage and the grassland with strip arrangement of Caragana. For the conservation tillage farmland and the grassland with Caragana belts, the aeolian sand flow is mainly concentrated on the height less than 40 cm above the ground surface, accounting for about 90% of the total sediment discharge, while for the traditional cultivated farmland and the degraded grassland, the aeolian sand flow is mainly below 20 cm, which accounts for more than 85% of the total sediment discharge.