Experimental Study on Nitrate Transport for Different Fertilization Methods

Nitrate leaching to groundwater is one of the major nitrogen losing ways in dryland farming system. The major season of nitrate leaching is rainy season in summer as corn growing, with strong intensity of rainfall (from July to September) in the Loess Plateau region. Localized compaction ridge fertilization method is a nitrogen fertilizer application that has theoretical basis on the water flow barrier and local ridge tillage, and it is assumed that less fertilizer leaching would occur. In this paper, the nitrate transports under localized compaction ridge (which made by hand), ridge without compaction and plate fertilization method are studied. Results of the experiment show that under the same amount of supply water, nitrate of plate fertilization method is easier to move than that of ridge fertilization method as water distribution difference. In prophase of growth period, there is no notable difference in nitrate movement among localized compaction, ridge and ridge without compaction fertilization method for roots of plant absorbing and/or holding up the nitrate. In the later stage, the corn needs little fertilizer, nitrate can be held up in the upper soil with localized compaction ridge fertilization method. In the corn harvested season, depth of nitrate leaching under plate fertilization method is the largest(>60 cm), while that under ridge without compaction fertilization method is mediate(>45 cm), and that under localized compaction and ridge is the smallest(＜35 cm).