| The problem of soil erosion on the Loess Plateau is a key environmental issue of concern to the whole society.It is receiving more and more attention from scientists in this field.The area belongs to semi-arid and semi-humid areas.The thickness of the aeration zone is large.The groundwater is buried in the deeper soil layer.When the rainfall intensity exceeds the soil infiltration capacity,surface runoff is generated.Therefore,studying the soil infiltration performance of the Loess Plateau is of great significance for solving soil erosion and flood forecasting.Scholars' research on soil infiltration in the Loess Plateau mainly focuses on sloping farmland,and many achievements have been made in this research field.The Loess Plateau of Zizhou,Shaanxi Province has the longest-stricken all-crushed natural siltation site on the Loess Plateau.This paper compares the sedimentary soil with the surface soil of other different underlying surface aeolian loess to study the loess area.The characteristics of soil infiltration rate are of great significance for soil and water conservation in this area.The soil permeability performance directly reflects the important hydrological processes of the soil.Based on this,it is also possible to analyze the possible soil water infiltration in the same area,such as the runoff,flow rate and infiltration of the soil under certain precipitation conditions.The ability of water transport and redistribution has great influence,and it is a reference factor for the setting of soil and water conservation measures.It is of great significance for water resources assessment and ecological construction research.In this paper,the loess sinensis in Zizhou County of Shaanxi Province was selected as the research object.The silt corn field and other four underlying surface loess were selected,and the field double-ring infiltration experiment and soil drilling sampling were carried out in the area,and the particle size and bulk density of the soil samples were carried out.The magnetic susceptibility was measured to study the soil infiltration characteristics and main influencing factors of different underlying surface of loess.Get the following conclusions:(1)Particle size is one of the influencing factors of soil infiltration rate in different surface layers of underlying surface.The composition of soil particles above 2 m in the Loess Plateau is dominated by silt,followed by gravel and clay.The average grain size of the soil in the silted corn field is smaller than that in the grassland and woodland.The soil particles in the A,B and C plot that are farther from the dam are thicker,and the soil particles in the D,E,and F plot are closer to the dam.After erosive rainfall,the surface runoff carries the soil particles on both sides into the gully.During the process of transporting the sediment,the slope of the gully gradually flattens,the water flow is insufficient,and the coarse particulate matter gradually deposits in the upstream area,and the fine particulate matter continues to be After handling,the fine particulate matter is gradually deposited after entering a gentle and stable environment.(2)Porosity is one of the influencing factors of soil infiltration rate in different surface layers of underlying surface.The soil porosity in the surface of the study area decreases with the increase of soil depth,indicating that the proportion of pores in the soil decreases with the increase of soil depth.In general,the porosity of the soil on the underlying surface of the aeolian loess is relatively large,and the porosity of the soil in the silt is small.Due to the development of macropores such as roots and holes in the aeolian loess,the soil has large pore diameter,good connectivity and rapid water infiltration;the sedimentation is water into loess,the large pores in the soil are not developed,the pore diameter is small,and the connectivity is poor.Water infiltration is slower.(3)The law between soil magnetic susceptibility and infiltration rate is not obvious,and the impact of human activities on soil infiltration rate is not significant.The soil magnetic susceptibility of different land types varies greatly,and the high and low frequency magnetic susceptibility of grassland and woodland are relatively high.It is speculated that the disturbance of human activities may be related to soil formation process.The magnetic susceptibility of the A plot ground to the F plot in the silted corn field is small.It is possible that the soil is ground by water for a long time,and the reduction causes the destruction of the ferrimagnetic minerals.The soil magnetic susceptibility of the silted corn field is low.(4)The infiltration rate of surface soil of aeolian loess is generally greater than that of aeolian loess.The infiltration rate of the four underlying surface soils of the aeolian loess,namely jujube forest land,apricot forest land,flat grassland and slope grassland,is significantly higher than that of silt corn,and the average infiltration rate of the former is 1.62 mm/min.The average infiltration rate was 0.89 mm/min.Because the aeolian loess is mainly formed by the action of wind.The silt is a layer of water-forming soil,which is formed by the flow of water and is formed by the accumulation of loess.It has a horizontal bedding structure,and this horizontal bedding structure slows down the ability of water to infiltrate vertically.Therefore,the reason for the formation of different soil layers is the main factor of the difference in infiltration rate between silted corn and aeolian loess.(5)The variation law of aeolian loess is not obvious.After analyzing the grain size,porosity and magnetic susceptibility of the surface soil of four samples of aeolian loess,the relationship between the obtained law and the law of soil infiltration rate is small.Because the aeolian loess is also affected by various factors such as vegetation types and slopes,the internal mechanism is more complicated,and the obtained infiltration rate of surface soil is not obvious,which needs further research.(6)The steady infiltration rate of the water-forming loess A to the F plot is gradually decreasing.Since the silted corn field is water-forming loess,the coarse particles are gradually deposited upstream,and the fine particles are transported to the downstream to gradually deposit.Based on the fitting degree and correlation coefficient between the three empirical infiltration models and the measured infiltration data,the Cossack formula can accurately describe the change of soil infiltration rate in the studyarea,with the highest degree of fitting,followed by The Horton formula,and the empirical infiltration formula fitting effect is poor,indicating that the Kostivok model is in line with the actual situation of loess infiltration. |
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