[Impact of localized compaction and ridge fertilization on field nitrate transport and nitrate use efficiency]

The primary season of nitrate leaching in the Loess Plateau region is the monsoon, which is caused by heavy rainfall during the growth season of corn (Zea mays L.). Nitrate leaching to groundwater is an increasing concern in agriculture, and is one of the major nitrogen losing ways in dryland farming system. Localized compaction and ridge fertilization is a method for nitrogen fertilizer application, by which, less fertilizer leaching would occur. The NO3(-)-N transport in soil profile, corn yields and nitrogen use efficiency under localized compaction and ridge fertilization were investigated through two years field study. The factors that affect NO3(-)-N transport under localized compaction and ridge fertilization were studied, combined with simulated experiment. The results showed that NO3(-)-N was leached to below 90 cm in plat fertilization in the year of about 370 mm rainfall, a mean precipitation during the season, while the NO3(-)-N leakage of the fertilizer zone was reduced by localized compaction and ridge fertilization, as a result that the NO3(-)-N concentration below 60 cm was less than 10 mg.kg-1, and NO3(-)-N accumulated in 20-40 cm with a concentration 80-90 mg.kg-1. There was no significant difference in yield between application methods with 240.0 kg N.hm-2. However, the absorbed amount of nitrogen was improved significantly by localized compaction and ridge fertilization, and the nitrogen use efficiency was increased by 9%. The bulk density of the barriers had an evident effect on NO3(-)-N transport under localized compaction and ridge fertilization, but the effect of ridge slope was insignificant.