| The objective of this paper was to study the soil properties, hydraulic parameters, the macropore properties with CT scanning and coloration methods in three main kinds of paddy soils (Bai soil, Huangni soil and Wushan soil) in Tai Lake region, and to study transport mechanism of Nitrate-N with field experimentation and soil column simulation. The results should provide basic parameters and scientific guides to environmental protection and macroscopical decision-making of agriculture.The results were as follows:1. The field capacities, available water contents and wilt coefficients in three paddy soils obtained from soil moisture characteristic curves. The field capacity was significant negative correlated with bulk density and significant positive correlated with soil structure coefficient, soil aggregation and organic matter content. In addition, available moisture content was negative correlated with soil texture. The wilt coefficient was positive correlated with soil texture.2. The results showed that saturated hydraulic conductivities of undisturbed soil were between 5.16×10-4 and 11.62×10-4cm.s-1. The saturated hydraulic conductivities of disturbed soil were between 0.76×10-4 and 3.31×10-4 cm.s-1. The saturated hydraulic conductivities of surface layer in the soil profiles were the largest. There was a degressive trend as the increase of soil depth. The saturated hydraulic conductivity of undisturbed soil was higher than that of disturbed soil in the same soil layer. All of the basic soil properties have relativity with the soil saturated hydraulic conductivities.3. The breakthrough curves (BTC) of vertical transport of nitrate-N and its infection factors of the three main paddy soils in Tai-Lake region were studied by the simulated soil column. When the flow velocity of nitrate-N was lower, the break through process of nitrate-N was prolonged from the surface layer to the bottom in the soil profiles. Among the three soils, the average flow velocity of Wushan soil was the smallest and the breakthrough process was the longest. When the soil was saturated and filtered adequately, nitrate-N could penetrate the soil column. The transport of nitrate-N was affected by clay content. As the clay content increased, the outflow of nitrate-N was retarded. The starting time of breakthrough of nitrate-N delayed, and the peak value of BTC decreased, the area of BTC became wide and the BTC became gently. All of the BTC were dissymmetric. The trail of curve was delayed more obviously when the clay content was larger. The vertical transport of nitrate-N was also affected by the soil bulk density and the organic matter content. When soil bulk density was small and organic matter content was high, the outflow of nitrate-N became fast and the starting time brought forward. When the organic matter content was...
|
PDF Full Text Request