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The Study of Preferential Flow Characteristics in Typical Black Cultivated Soil

Author: JiangXiaoJin
Tutor: ChenXiangWei
School: Northeast Forestry University
Course: Soil and Water Conservation and Desertification Combating
Keywords: Typical black soil Preferential flow Water movement Dye tracer Breakthrough of water
CLC: S152.72
Type: Master's thesis
Year: 2011
Downloads: 99
Quote: 1
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Abstract


Taking the cultivated soils in typical black soil region of Northeast China as test objects, by using dye tracer and double-ring infiltrometer techniques to research the surrounding characteristic; and by using breakthrough of water on the soil column from different depth to discuss the non-equilibrium characteristic of preferential flow; and testing the combining method of dye traces and hood infiltrometer on studying macropore flow. Through measuring and analyzing the dye stained width、dye coverage of soil transverse and longitudinal sections、the field maximum dye stained depth、infiltration rate、outflow rate and photograph interpretation, this paper aimed to approach the water flow movement pattern and distribution characteristics in typical black cultivated soils. The results may serve as theoretical basis for scientifically improving the water and fertilizer utilization efficiency during management and operation of agricultural soil.The results showed that:At soil depth 0～15.0cm, matrix flow was the main soil water flow movement pattern; at depth 15.0～20.0cm, lateral flow was observed, and the dye stained width and dye coverage reached their maximum, being 25.6cm and 20.73% respectively. At depth 20.0-67.0cm, the main soil water flow movement pattern was macropore flow, with cracks and macropores as the main preferential routes. The cracks at depth 20.0～35.0cm made the preferential flow have distinct surrounding characteristic and the macropores at depth 40.0～67.0cm were the main preferential routes. Due to the existence of the preferential routes of cracks and macropores, the migration velocity of water in soil increased by 4.5 times, which could not only cause water loss, but also accelerate the migration of pesticides to ground water.Although the differences among the water flow movement patterns, the non-equilibrium flow was appeared on the soil depth of 0～5.0cm、15.0～20.0cm、20.0～25.0cm、40.0～45.0cm. The fluctuation of rate that water flow through soil at depth of 20.0～25.0cm、40.0～45.0cm changed over time, which indicated the non-equilibrium characteristic of preferential flow, especially the bigger differential value between the infiltration rate and outflow rate, the cumulative infiltration and cumulative outflow of water flow through this two layers soil. This was because the part of water was entering into the soil matrix when the water flow through the preferential routes that existing in this two layers soil. It was the basic reason that caused the non-equilibrium characteristic to appear.The macropore flows initiated under three pressures heads of -5.0cm,-3.0cm and -1.0cm, and lower pressure (-5.0cm and -3.0cm) resulted in more lateral flow. Amount of lateral flow between different pressures was significant at 25cm depth (p<0.05). Soil of 40.0～74.3cm was less disturbed giving rise to good continuity with effective macro porosity of 0.007%. For the pressure heads of -5.0cm,-3.0cm and -1.0cm, the maximum depths of dye staining were 74.3cm,60.7cm and 64.7cm and the dye stained width were 45.9cm,45.0cm and 52.1cm at the depth of 14.0～28.0cm respectively. Soil under pressure head of -3.0cm had the biggest initial infiltration rate of 7.6mm/min but smallest steady infiltration rate of 2.4mm/min. Soil under pressure heads of -5.0cm had best connectivity of macropore paths. The combining method was a better method on studying macropore flow in field.

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CLC: > Agricultural Sciences > Agriculture as the foundation of science > Soil > Soil physics
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