Experimental Analysis of the Effective Depth of Interaction of Rainfall-Surface Runoff-Soil Nitrogen

As one interaction outcome of soil nitrogen with rainfall and surface runoff, soil nitrogen loss by runoff virtually is the mass transfer among different carriers, runoff, sediment and soil, etc. Rainfall and surface runoff are main impetuses. Soil is the interface on which the interaction takes place, and the "motherland" from which the nitrogen transports. The soil nitrogen involved in loss by runoff only exists in certain soil horizons, the depth of which is named as Effective Depth of Interaction (EDI). Take the soil mineral nitrogen (NH₄ ⁺ and NO₃ ^- ) for example. According to the results of simulated rainfall experiment, the EDI of soil nitrogen is analyzed, and the methods to confirm EDI of both NH₄NO₃-applied experiments and no- NH₄NO₃-applied ones are recommended. Meanwhile the two methods\´ applicability for other chemicals is discussed here. The results are in the following. First, with the same type of fertilization, there are no evident influences of different fertilizer amount on the EDI. Second, the infiltration, transport by runoff and EDI distribution of nitrogen are controlled by the various characters of ions. The EDI of soil NO₃ ^- is deeper than that of soil NH₄ ⁺, the balance 3~9 cm. Third, the EDI distribution takes on spatial changes along the slope, deeper in the middle and lower parts, while shallower in the upper part.