Abstract
In a no-tillage system, the application rate of herbicides increases more than the conventional tillage system. To lower environmental pollution, the application rate of herbicides needs to be reduced. The objective of this study was to investigate the effects of the co-situs application of controlled availability fertilizer and row app1liation of herbicides on the yield of dent corn (Zea mays L.) in comparison with the surface application of readily available fertilizer and whole or no herbicide application in no-tillage cultivation. Field experiments were conducted for two years (1998-1999) in Andisol. No herbicide application increased the biomass and nutrient uptake of weeds and decreased those of dent corn compared with the whole application of herbicides. In co-situs application plots, yield and nutrient uptake of dent corn tended to be higher than those in surface application plots. In the case of no application of herbicides, biomass and nutrient uptake of weeds in the row of co-situs application plots were increased more than those of the surface plots. Row application of herbicides reduced biomass and nutrient uptake of weeds per row compared with no herbicide application. A combination of co-situs fertilization and row application of herbicides increased the nutrient uptake of dent corn and yield compared with the no herbicide application or surface fertilization. As stated above, a combination of co-situs fertilization using controlled availability fertilizer and row application of herbicides is feasible to reduce the application rate of herbicides and to restrain reduced yields in no-tillage dent corn cultivation. However, the yield of this combination is less than that of the full application of herbicide because of the increase in weed biomass inter-row. This needs to be solved in the future.
