| In the soil and mountainous areas in the south of China,the cultivated land has a large proportion of cultivated land,which is an important agricultural resource in the mountains and a source of soil erosion.Soil and water erosion on the one hand silt up rivers,reservoirs and other water conservancy projects,shortening the service life of the project;on the other hand,it causes problems such as thinning of the soil layer,loss of nutrients,and decreased soil fertility,especially in the southwestern mountainous areas where carbonates are widely distributed.The problem of desertification of land has been highly concerned by the government,research groups and people.Soil erosion problems on sloping farmlands are different from those on other land types such as forest land and grasslands.Soil properties,topography,and rainfall are not easily controlled,and crop types and planting patterns become variable factors that affect soil erosion.In view of this variable factor,this study intends to design soil erosion simulation experiments with different rainfall intensity,slope and planting patterns through field investigations in order to reveal the soil and water conservation mechanisms of different planting patterns and propose the best soil and water conservation intercropping model.Three rain intensity(60mm/h,90mm/h,120mm/h)and three slopes(15°,20°,25°)were set in the experiment,and seven different simulated planting patterns were used for cross-over simulation experiments.Specifically,a single mode with an average height of 15 cm,a single mode with 60 cm,a single mode with 200 cm,an interplanting mode with an average height of 15+60 cm,a interplanting mode with 15+200 cm,a interplanting mode with 60+200 cm,and 15+60 +200cm interplanting mode.Based on the statistical analysis of experimental data,preliminary conclusions are drawn:(1)In the early period of rainfall,the soil moisture content is low,the infiltration capacity is strong,and the runoff on the slope surface is difficult;as the rainfall duration increases,the soil moisture content increases,the infiltration capacity decreases and tends to stabilize,and the slope surface begins to produce flow.After the initial surface runoff from 5 minutes to 10 minutes,the inner diameter flow rate increases rapidly.After that,the soil moisture content is saturated and the infiltration capacity is basically unchanged,thus forming a relatively stable slope runoff.At 60 mm/h,90 mm/h,and 120 mm/h,the average runoff of the 200 cm single model was 12.99 ml/s,18.69 ml/s,and 23.83 ml/s,respectively.The average runoff of the 60 cm single model was 10.09 ml/s,14.98 ml/s,and 20.97 ml/s,respectively.The average runoff of the 15 cm single model was 8.75 ml/s,13.54 ml/s,and 18.31 ml/s,respectively.The average runoff of the 15+60 cm intercropping model was 8.49 ml/s,12.68 ml/s,and 17.17 ml/s,respectively.The average runoff of the 60+200cm intercropping mode was 10.54 ml/s,15.22 ml/s,and 19.43 ml/s,respectively.The average runoff of the 15+60+200 cm intercropping mode was 7.5 ml/s,11.78 ml/s,and 16.64 ml/s,respectively.The total runoff of the seven planting patterns is as follows: 200 cm single mode> 60 cm single mode> 60+200cm interplanting mode> 15+200cm interplanting mode> 15 cm single mode> 15+60cm interplanting mode> 15+60+200cm interplanting mode.The single-model high-till crop has larger runoff,and the high-and low-crop intercropping model has less runoff.(2)Compared with the single model,the variation of sediment concentration between the high and low cropping models was the smallest.In the 200 cm single model,the 60 cm single model,and the 60+200cm intercropping model,with the increase of the rainfall duration,the sediment concentration and the change range of the runoff during the whole process are relatively large.Among them,the 200 cm single model has a runoff sediment concentration of 0.0074.Runoff sediment concentration between 0.0004-0.027g/ml for 60-cm single model and 0.006-0.041g/ml for 60+200cm runoff between-0.064g/ml and 60cm;single model for 15 cm The sediment concentration and variation of runoff in the 15+60cm intercropping model,the 15+200cm intercropping model,and the 15+60+200cm intercropping pattern were small,and the runoff sediment concentration first decreased with the increase of rainfall duration.Afterwards,it gradually became stable;among them,the sand content of 15+60+200 cm cropping pattern varied the least and was between 0.00001-0.005g/ml.(3)Compared with the single model,the total erosion of the single-pattern high-crop single-cropping system under the condition of the single rainfall was larger,and the erosion of the low-crop interplanting model was smaller.Among them,200 cm single model had the largest amount of erosion,and 15+60+200cm had the least amount of erosion.When the rain intensity is 60mm/h,90mm/h,120mm/h,the total erosion of the 200 cm single model is between 464-770 g,704-1997 g,and 1024-2890 g under different slopes.The total erosion of the 60+200cm intercropping model was between 111-368 g,279-832 g,and 518-1139 g,respectively.The total erosion of the 60 cm single model was between 14-131 g,207-449 g,and 649-1428 g,respectively.The total erosion of the 15+200cm intercropping model was between 60-100 g,90-299 g,and 126-183 g,respectively.The total amount of erosion in the 15+60 cm intercropping model was between 23-52 g,28-75 g,and 42-63 g,respectively.The total erosion of the 15 cm single model was between 4-21 g,54-26 g,and 65-86 g,respectively.The total erosion of the 15+60+200cm intercropping model was between 3-9g,14-37 g and 54-119 g,respectively.The results showed that the total erosion of single-crop pattern(60cm single,200 single)and 60+200cm intercropping pattern was higher,while the 15 cm single pattern,15+60cm,15+200cm and 15+60+200cm intercropping.The total amount of erosion is relatively small.Therefore,interplanting low crops is the key to controlling soil erosion in slope farmland.(4)Compared with the single model,the interplanting time of the single model was earlier,and the starting point of the 200 cm single model was the earliest.Under 60 mm/h,90 mm/h,120 mm/h rainfall intensity and different gradients,the mean start time of the 200 cm single mode was about 1.5 min,1.27 min,and 1 min.Followed by the 60 cm single mode and 60+200cm intercropping mode,the start of flow is earlier.15 cm single species,15+60cm intercropping,15+200cm intercropping,15+60+200cm interplanting and other modes began to produce slower flow time.Among them,the average of the onset time of flow in the 15+60+200cm intercropping mode was approximately 2.65 min,2 min,and 1.82 min.The interplanting mode started with the slowest time.(5)Compared with the single model,in the composition of eroded sediment particles,the eroded sediment in the low single crops and the high and low collocation modes are dominated by silt;the single silt eroded sediment is dominated by sand grains.the Lord.The eroded soil particles in the 200 cm single and 60 cm single models were dominated by sand grains,and the fine sand accounted for the highest proportion,accounting for 47.89% and 40.83%,respectively.The eroded soil particles in 15 cm single species,15+60cm intercropping,15+200cm intercropping and 15+60+200cm intercropping modes were mainly coarse powder or fine powder.During the whole process of soil erosion,the soil erosion particles are changing.The proportion of clay particles and fine particles in the first half of the soil erosion particles is higher than in the second half;the corresponding sand particles are lower than the latter half.(6)Through systematic analysis,compared with the single model,the interplanting model has better soil and water conservation benefits,and in the interplanting model,interplanting low crops is the key to control the soil erosion of slope farmland.Combining cultivation practices in southwest mountainous regions,interplanting crops such as beans,potatoes,and sweet potatoes in corn fields will not only be beneficial to the prevention and control of soil erosion in the region,but will also help improve land utilization and increase crop yields. |
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