| Yellow soil is second soil types of sloping cropland in Sichuan Province,the rainfall around the Sichuan basin northwest yellow soil area is abundant,due to the prominent contradiction between human and land,that a large number of scattered farmland,combined with the unreasonable tillage practice,resulting in serious soil erosion,that not only leads to soil degradation and land productivity decline,but also increase the environmental load and risk of water,seriously hindered the sustainable development of regional agriculture and the construction and protection of ecological environment in the yellow soil area.As one of the main crops of corn planted in yellow soil slope cropland,its growth period has the characteristic of coincidence with the rainy season in the yellow soil area.Field runoff plots and laboratory analysis were used to study on soil erosion resistance,reveal the response law that the different growth stages of corn effect on the variation characteristics of surface runoff,subsurface runoff and sediment yield,clear coupling relationship that between different growth stages of corn,soil erosion resistance and surface runoff,sediment yield during the whole growth stages of corn(seeding stage,jointing stage,tasseling stage and maturing stage)with the objective tillage method of cross ridge,along with the control of longitudinal ridge in area of 8 m2 projection(4 m × 2 m)with slope runoff plots 10° and 15° degrees that was located in Guankou town in Dujiangyan City in the Sichuan Province of China.Therefore,this study would provide a theoretical evidence for sustainable development of agriculture in the yellow soil area and construction of ecological barrier in the upper reaches of Yangtze River.Main research results are as follows:(1)For the cross ridge,MWD(mean weight diameter),GMD(geometric mean diameter),SC(soil aggregate stability coefficient)and AD(soil aggregate degree)of soil dry-aggregates and water-stable aggregates significantly increased with the growth stages of corn.The MWD,GMD,SC and AD of soil aggregates with the cross ridge were significant higher than those with the longitudinal ridge.However,the D(fractal dimension),SFR(soil structure failure rate)and DC(soil dispersion coefficient)decreased with the growth stages of corn,meanwhile,the D of soil aggregates with the cross ridge were significant lower than those with the longitudinal ridge.SAI(Soil anti-erodibility)of cross ridge significantly increased with the growth stages of corn.There were significant positive correlations between SAI and soil organic matter,bulk density.In the root parameters of corn,SAI was positively correlated with root density,root surface area,root volume,total root length and root length of different root diameter.(2)SA(Soil anti-scourability)of cross ridge significantly increased with the growth stages of corn,and enhancement effect of corn root on SA was mainly reflected in the tasseling stage and maturing stage.SA of cross ridge decreased significantly with the increase of scouring flow.SA extremely significant positive correlation with soil bulk density,organic matter content and>2 mm,1-0.5 mm water-stable aggregates significantly,but extremely significant negative correlation with<0.25 mm water-stable aggregates.In addition to root mean diameter,SA of cross ridge and different root parameters showed significant positive correlation.(3)SS(Soil shear strength)and enhancement effect of cross ridge significantly increased first and then decreased with the growth stages of corn,and SS reached themaximum in the tasseling stage.There existed significant linear function between SS and soil moisture,and there was extremely significant linear correlation between SS and soil bulk density.In addition to root mean diameter,SS of cross ridge and different root parameters showed extremely significant positive correlation.(4)Average rainfall of the study area was 715.19 mm for two consecutive years,the amount of erosive rainfall accounted 18.91%and 52.35%of the cumulative erosive rainfall in the tasseling stage and maturing stage.During the whole growth period of corn,sediment yield and runoff of cross ridge increased with the growth periods after jointing stage,and the two changes were synchronous,and sediment yield was significantly influenced by runoff,and quantitative characterization of available power function(y=axb,a>0 and b>0)of runoff and sediment yield.Rainfall intensity and plant height as the main factor were runoff with cross ridge.Rainfall intensity,SA and SS as the main factor were sediment yield with cross ridge.With the growth periods,sediment concentration of tasseling stage and maturing stage were significantly higher than that seeding stage and jointing stage.(5)SAI,.SA and SS of 10° slope were significantly higher than that of 15° slope of cross ridge at different growth stages of corn.SAI and SA of 0-10 cm soil layer were significantly higher than that of 10-20 cm soil layer of cross ridge at different growth stages of corn,however,SS of 0-10 cm soil layer was significantly lower than that of 10-20 cm soil layer of cross ridge at seeding stage,jointing stage and tasseling stage of corn.Surface runoff of 10° slope was significantly lower than that of 15° slope,however,20 cm and 40 cm subsurface runoff of 10° slope were significantly higher than that of 15°slope of cross ridge at tasseling stage and maturing stage of corn.Sediment yield and sediment concentration of 10° slope were significantly lower than that of 15° slope of cross ridge at tasseling stage and maturing stage of corn.Compared with longitudinal ridge,the implementation of cross ridge strengthened soil stability,enhancing SAI,SA and SS,leading to significantly reduce sediment yield. |
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