Soil Erosion Characteristics Of Young Orange Orchards Slope In Northwest Guangxi

In recent years,the area of orange orchards in northwest Guangxi has expanded.The erosion mechanism of orange orchards in the main soil types(red soil,limestone soil)in northwest Guangxi is still unclear.Therefore,this study explored the effect of some factors like rainfall intensity(30mm/h,90mm/h),slope(10°,20°),initial soil moisture(dry,wet)on the erosion of orange orchards in Northwest Guangxi,reveal the occurrence and development mechanism of soil erosion in orange orchards from multiple angles.The main research conclusions are as follows:(1)The runoff of red soil orange orchard was mainly surface runoff,followed by soil subsurface flow,and subsurface runoff was the least.In the process of runoff,the generation time of each runoff component in red soil orange orchard was earlier than that in limestone soil orange orchard,and the surface runoff intensity is higher than that of the limestone soil orange orchard.Under 30mm/h rain intensity,the steady surface runoff intensity of the high-slope(20°)red soil orchard was 13.95 times that of the limestone soil orchard.Under90mm/h rain intensity,the stable surface runoff intensity of 10°,20° red soil orange orchard was 1.34 and 2.70 times that of limestone soil orange orchard.However,the runoff intensity of soil subsurface flow and subsurface runoff were small that does not exceed 5mm/h.When it began to produce runoff,it had no obvious fluctuation and showed a very slow linear growth trend.Therefore,the soil subsurface flow and subsurface runoff of the red soil orange orchard were small,and the surface output was the main one.(2)Under 30mm/h rain intensity,the runoff of limestone soil orchard was dominated by soil subsurface flow and subsurface runoff,the surface runoff was s mall,and there is no surface runoff in the orange orchard.Under 90mm/h rain intensity,the surface runoff increased,and the 10° limestone soil orange orchard was dominated by surface runoff,and 20°orange orchard was still dominated by soil subsurface flow and subsurface runoff.Under different rainfall intensities and gradients,the soil subsurface flow and subsurface runoff in limestone soil orange orchard was more than that in red soil orange orchard,and its runoff production process was obviously different from that of red soil orange orchard,which is characterized by rapid growth in the early stage of runoff and stable runoff in the middle and late stages.Its runoff intensity is higher than that of red soil orange orchards,so it can produce more soil subsurface flow and subsurface runoff.(3)Under 30mm/h rain intensity,the amount of sediment loss and sediment concentration in limestone soil orange orchard was less than that in red soil orange orchard.The total sediment loss of red soil orchard and limestone soil orchard were 161.95 g and 0.03 g at low slope(10°),and 320.49 g and 0.59 g at high slope(20°).The amount of sediment loss from limestone soil orange orchard was less than 1% of that of red soil orange orchard.Under the rain intensity of 90mm/h,the runoff sediment content of lime soil orange orchard was larger than that of red soil orange orchard.And the total amount of sediment loss in the red soil orange orchard and limestone soil orange orchard at low slope(10°)were 223.05 g and637.53 g,and at high slope(20°)it were 619.64 g and 246.55 g.It is necessary to control the sediment loss of limestone soil orange orchards at all slopes and red soil orange orchards with low slope under rainfall intensity of 90mm/h,and also to control the sediment loss of red soil orange orchards at all slopes under rainfall intensity of 30mm/h.(4)Surface runoff,soil subsurface flow,and subsurface runoff in wet orange orchard began to produce runoff earlier than that in dry orange orchard,and the runoff was easier to reach a stable state.The surface runoff and total runoff of wet orange orchard were more than those of dry orange orchard.After changing from dry state to wet state,the proportion of runoff from various runoff components of the red soil orange orchard remained unchanged,the total amount increased.Its average proportion of surface runoff,soil subsurface flow and subsurface runoff were 83.80%,9.82% and 6.40%.The proportion of surface runoff and subsurface runoff of limestone soil orange orchard increased by 18.19% and 13.42%respectively,while the proportion of soil subsurface runoff decreased by 31.61%.