| Farmland is one of the basic factors of agricultural production. Preferential flow phenomena of soil has a significant impact on the utilization of soil water and solute preferential transport in soils. In this paper, agricultural land of Chongqing Simian Mountain were selected to analyze the depth of dye infiltration and the rate of infiltration under different antecedent soil moisture and then research the effect of antecedent soil moisture on preferential flow. Through the establishment of drying and wetting treatment, using dye tracer method, TDR method and image processing techniques. At the same time, analyze the effect of antecedent soil moisture on solute preferential transport through experiments of soil column with artificial macropores.The results showed that:(1)In the plot with lower antecedent soil moisture, the wetting front velocity decreased with depth, the average estimated wetting front velocity was 1520 mm/h. Whilst in the plots with higher antecedent soil moisture, the wetting front velocity increased with depth, the average estimated wetting front velocity was 515 mm/h.(2)The maximum depth of dye infiltration in the plots with lower antecedent soil moisture was 56.00 cm, and the maximum depth of dye infiltration in the plots with higher antecedent soil moisture was 33.76 cm, indicating that the maximum depth of dye infiltration with lower antecedent soil moisture was deeper than that with higher antecedent soil moisture. In the plot with lower antecedent soil moisture, preferential flow occurs mainly in top soil layer and at a depth of 20-30 cm in heart soil layer, whilst in the plots with higher antecedent soil moisture, preferential flow occurs in top, heart and substrate soil layer. And the average percentage of stained area of each layer of vertical section and horizontal cross-section in the plots with lower antecedent soil moisture was larger than those with higher antecedent soil moisture, indicating that the phenomenon of preferential flow in the plots with lower antecedent soil moisture was more obviously.(3)The steady effluent rate of the dye-stained area and dye-unstained area in the plot with lower antecedent soil moisture were more than that in the plot with higher antecedent soil moisture. And water breakthrough curves in the plot with lower antecedent soil moisture had a bigger fluctuation. The number of soil macropores of each radii in the plot with lower antecedent soil moisture was larger than that n the plot with higher antecedent soil moisture. And the macroporosity of the dye-stained area in the plot with lower antecedent soil moisture was larger.(4)Preferential flow phenomena and solute preferential transport was more obviously in soil column with lower antecedent soil moisture. The preferential transport of non-adsorption solute in soil column with lower antecedent soil moisture was more obviously which breakthrough earlier and recovery higher. The recovery of total phosphorus in the soil columns with different antecedent soil moisture were below 18% and lager of adsorption solute was absorbed by the soil column particle. Its breakthrough was also earlier and its peak value of effluent relative concentration was higher, but Its solute preferential transport phenomena was not obviously. |
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