The Transformation About The Wheat Root Distribution Features Affected On The Erosion Prevention Mechanism On Loess Plateau

Slope farmland of the loess plateau is an important source of soil erosion. Crops on hillyland determines the ecological benefit and economic benefit of farmland, is the key factor ofsoil erosion on the slope, so the further study of crop root system and the relationship betweensoil erosion, to better improve crops on hilly land function evaluation and scientificproduction is of great significance. For discussing about the conservation of water and soil onthe loess plateau slop farmland, and the transformation on the physic properties, like shearstrength, soil anti-scourability, disintegration of soil and the infiltration. Choosing the winterwheat，soybean, and millet as materials, which were the common slop land crops on LoessPlateau. Plant the crops on the runoff plots on common farming methods, and on differentstage of the crops, determined the soil physic properties, and then, experiment on theimitation rainfall, measured the transformation about the flow and sediment. Exploring theprocedure of the crop root density distribution features affected on the erosion preventionmechanism. Research results indicated that：1. The root weight density and the length density of crop changed with the slop and soildepth. And the slop was the main factor to the transformation on slop farmland. The soilvolume weight had a significant impact on the surface of the slop farmland, proceeding to theaffection on the erosion prevention mechanism. With the deepening of soil, root weightdensity and root length density decreases continuously, soil bulk density increases slightly.With the increase of the slope, the root density of root weight and root length density isreduced, and increased root length density, soil bulk density is smaller.2. Crop root soil disintegration rate had no obviously change in the direction of the soildepth, but intensely, changes in the slope on the transverse shear force on the slope is different.When the root system began to growing old, nearly soil surface instantaneous disintegrationrate is larger, and be faster to achieve stability. After the root system growth to a certain stage,root to the decrease of the average rate of disintegration effect was obvious. The order of theaverage disintegration rate was deep soil layer> surface layer> bare land. Under thecondition of different slope, looking from the soybean disintegration rate comparison, the greater gradient the bigger the disintegration rate was. For different growth period, theaverage rate of disintegration was, in fact, reducing as the root weight density.3. The crop root had significant effects on farmland soil restitution. The impact coefficientrestitution of bare soil in general with the increase of the depth, the soil is more compact, thegreater the shear strength; But the crop coefficient of restitution was also affected by the root,the greater the density of root weight and length density of near surface, the greater the impactcoefficient of soil is larger. To different gradient, the greater of the slope, the more of the rootson deep soil layer, the more compact to the soil, the greater of the impact coefficient ofrestitution. The root weight and root length density and soil shear strength strong linearcorrelation.4. The root of the winter wheat could increase the soil water infiltration, thus it could makethe soil infiltration rate greater than bare soil. The winter wheat root infiltration process, thebeginning will change soil initial infiltration rate, and makes the initial infiltration rate, thebare land, the steady infiltration rate is also bare land is big.5. Bare soil’s shear strength increased with the increase of the depth, overall the compactedsoil, the smaller shear strength; Close to ground the greater the density of root weight and rootlength density, the greater the shear strength of soil. For different slope, soil shearing strengthand a negative correlation relationship between slopes, slope, soil shearing strength is smaller.After bare no root soil erosion, washed away is larger, the quality of the soil and root smaller;Bare rushed after the soil moisture basically saturated soil, root and soil erosion, has not yetreached saturation moisture content, density and root of consolidation of the soil and theeffect of soil.6. Crop root system has weakened the role of the runoff and sediment yield in the slope,leave the wheat root area can reduce26.4%of the biomass waste production flow, reduce thesurface soil loss by14.5%, the slope surface runoff was29.5L/m3, slope sediment yield is466.41g/m3.Crop root system with functions of retention of the sand, the root sedimentreduction effect relative to the water reducing effect is weak. Wheat in different growth periodheld the effect of sediment and water is different, the ultimate reason is the different wheatgrowth in different growth period of root. Wheat at the jointing stage of overall reservoirsediment reduction effect is best, it also and jointing stage the root of the density of rootweight and root length density is higher, the worst of the effect of water and sedimentreduction, growth period to maturity of wheat in the phase of the overall volume of the runoffand sediment yield. The growth period of wheat root weight density, root length density andsediment runoff and sediment yield a quadratic relationship, and root weight density influenceon runoff and sediment yield weighting. The runoff and sediment yield in the wheat root process line is different with the process of runoff and sediment yield in the bare land,15minutes before the start of the rains as the root area (R) is a slowly increase, the rainfall peakis about30min.