Soil moisture conditions can have a large effect on crop responses to nitrogen fertilization. Kentucky's usual climatic pattern of periods of heavy rainfall and relatively warm temperatures during the winter and spring seasons influences expected yield responses of corn to applied nitrogen. If nitrogen fertilizer is applied in late winter or early spring, some of it may be lost before the plants have made sufficient growth to take up appreciable quantities. The amount of loss that might be expected will be influenced by the amount of rainfall, temperature, amount of organic matter and drainage of the soil.
Miller, Harold F.; Wells, Kenneth; Bitzer, Morris J.; Thomas, G. W.; and Phillips, R. E., "Influence of Time of Application of Nitrogen Fertilizer on Corn Yields" (1975). Agronomy Notes. 121.