Variety Difference of Nitrate Nitrogen Concentration of Corn (Zea mays L.) under a Large Amount of Nitrogen Fertilizer Application.

Abstract

Variety difference of nitrate nitrogen concentration of corn (Zea mays L.) under a large amount of nitrogen fertilizer application was examined using the method developed by Harada et al. (Grassland Science 41, 352-356), that is, nitrate nitrogen concentration of the whole plant on the basis of dry weight could be estimate by multiplying the concentration factor by the dilution factor, defined as follows ; The concentration factor is nitrate nitrogen concentration of the stem on the basis of fresh weight and the dilution factor is dry matter partitioning ratio of the stem divided by dry matter ratio of the stem. Nitrate nitrogen concentration was highly correlated with the concentration factor, but not with the dilution factor. No significant correlation was found between nitrate nitrogen concentration and dry matter yield or nitrogen uptake. Lower concentration factors of the varieties were below 0.05%, and the maximum value of the concentration factor was 2-fold higher than the minimum value. On the other hand, the dilution factor decreased as milkline depression score increased, and there was significant correlation between the dilution factor and the milkline depression score. An average of the dilution factor in yellow ripe stage was below 2. Therefore, nitrate nitrogen accumulation ability of the variety could be evaluated by comparing the concentration factor. Choosing a variety of corn having lower concentration factor could depress nitrate nitrogen concentration to an level of about 0.1% in yellow ripe stage, if nitrogen was fertilized excessively.