Abstract:

【Objective】 Transport characters of soil water and solute on slope land in interval rain events are important to reduce soil and water loss and to protect water and soil resources in erosion region. 【Method】 According to the results of indoor simulation experiments of rainfall on loess slope land with spray-applied fertilizer or mixed-applied fertilizer, and the interaction of rainfall, surface runoff and soil, the soil erosion, transport characters of soil NO3-, Br-, and PO43- in two rain events with the interval of 24 hours were investigated. 【Result】 Results showed that the stable rainfall intensity, amount of runoff and sediment in the 2nd rain was usually more than that of the 1st one, and more quick for the surface runoff initiation and the stable period occurrence. Compared with the NO3- and Br- concentration in surface runoff of the stable content period in the 1st rain, the concentration of the surface runoff initiation in the 2nd rain was heigher than the former, while that of the stable content period in the 2nd rain was lower. The soil PO43- concentration in surface runoff in the 2nd rain, however, was usually heigher than that of the stable content period in the 1st rain. There was less surface loss amount of soil NO3- and Br- in the 2nd rain, with the result of its available infiltration and the content decreased in the upper layer. While the PO43- surface loss in the 2nd rain was 2.93 times and 1.77 times greater than that in
the 1st rain, for surface spraying treatment and mixed-applied one, respectively. 【Conclusion】 Therefore, for the vulnerable erosion loess slope, the solute content curve of surface runoff in the 2nd rain is not the extension of that of the former, as the result of the changing solute content and the antierosive ability of the upper soil. Affected by the erosive hazards, there will be more soil solute loss caused by continuous rainfall events. Some flow control measures are suggested for the initial rain event in rainy season to lessen the loss of soil non-adsorbed nutrient. The key to the latter rain is protection of soil and water and prevention of the loss of soil adsorbed nutrient.

Key words: interval rain events, surface runoff, infiltration, soil erosion, soil solute release and transport