| Vertical and horizontal transports of nitrate-N and influential factors in saturated-unsaturated soils were studied and characteristics of vertical transport of nitrate-N were described with CXTFIT model. Results were as follows:(1)The saturated hydraulic conductivities of all soil layers in the main three kinds of soil in the Huang-Huai-Hai Plain were changeable from 5.95 X 10-6 to 1.08 X 10-2 cm. s-1 and changed with increase of the depth. The highest saturated hydraulic conductivities occurred in topsoil layer and the lowest in middle soil layer. The saturated hydraulic conductivities were very different between undisturbed and disturbed soil and were affected by bulk density, porosity, organic matter content, and clay content.(2)Simulating the unsaturated hydraulic conductivities of the three kind of soils reduced with increase of soil water suctions by RETC model. When the soil water suctions were low, the unsaturated hydraulic conductivities in topsoil layers were higher than those in middle soil layers. While the soil water suctions increased to some values, the unsaturated hydraulic conductivities in middle soil layers were higher than those in topsoil layers.(3)Tendencies of the soil water retention curves of all soil layers in three kinds of soil were similar, the soil volumetric water content decreased with the soil water suctions. Simulated by RETC model and tested soil water characteristic curves fitted quite well and these relationships were sharply significant by statistic analysis.(4)The soil moisture diffusivity of all soil layers in the three kind of soils was changeable from 1.0 X 10-3 to 15 cm2, min-1 and changed with increase of the depth. When soil volumetric water content was constant, the high soil moisture diffusivity occurred in topsoil layers and the low in middle soil layers. Relationship between soil moisture diffusivities and soil volumetric water content in every soil layer was sharply positive exponential function, which was fitted by the empirical equation ( D( ) = aeb ), and this relationshipwas significant by statistical analysis.(5)In the process of the nitrate-N horizontal transport, the horizontal transport velocity of nitrate-N decreased with rise of the distance of the tracer source in power function, and this relationship was sharply significant by statistic analysis. Trends of the horizontal transport velocity of nitrate-N of all soil layers in three kinds of soil were correspondent, namely, the horizontal transport velocity of nitrate-N increased with the soil volumetric water content increase in each soil layer in three kinds of soil. The horizontal transport velocity of nitrate-N was affected by the soil moisture diffusivity, and these changes can be described by exponential function. This relationship was sharply significant by statistic analysis.(6)In the process of the nitrate-N horizontal transport, the concentration of nitrate-N slowly increased with increasing the distance of the tracer source in power function, the maximum of the concentration of nitrate-N occurred where there were wet and arid soil. The concentration of nitrate-N reduced with increase of the soil volumetric water content and the soil moisture diffusivity, and the former can be described in power function. This relationship was sharply significant by statistic analysis, too.(7)Under saturated soil condition and in the process of the vertical transport of the nitrate-N, a large part of the Breakthrough Curves (BTCs) of different concentration of nitrate-N (100mg L-1 200mg L-1 NO3- - N) overlapped, that is, vertical transport of nitrate-N wasn't influenced by different concentration of nitrate-N (100mg L-1 200mg L-1 NO3- -N) in soil column. Accompanying anion (SO42-) and co-existing cations (K+ andCa2+) weren't affected the form and peak value of BTC of vertical transport of nitrate-N in all topsoil layers of soil column, but the former made time of outflow of nitrate-N in all middle and low soil layers short, and the latter long. These phenomena were quite outstand...
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