Present study showed that N rates above 225 kg N ha-1 caused no additional increases in yield.
However, in the North China, 200 kg N/ha was recommended when considering both grain production
and environmental impacts[6], this distinction could be related to lower nutrient in sandy soil. Crop
cannot get additional N application from this poor soil, thus the demand for N fertilizer increased. A study
conducted on a Verndale sandy loam soil also showed that maximum maize grain yields were obtained
with 202 to 234 kg N/ha[7]. Although, this application rate was still evidently lower than the conventional
application rates of N fertilizer (350-450 kg N/ha) used by local farm. This study also indicated that the
irrigation amount of 12000 m2/ha was exceptionally excessive, could not increased the agriculture
production, but over-consumed water resources and lead to NO3
--N leaching to groundwater. A study by
Su and Chen [8]in same area confirmed this item.