Interaction of Mechanisms of Gaseous Losses of Nitrogen in Upland Soils

The effects of urea application on loss of nitrogen by ammonia volatilization under field conditions were estimated. Ammonia volatilization was related to pH and texture of the soil and method of fertilizer application. This loss of nitrogen was negligible during the first three days after fertilizer application. Thereafter, there was a sharp rise in the loss, reaching a peak value at ten days, followed by a gradual decline in the rate of loss and practically no loss occurred after twentyfive days of application. This observation is well supported by the yield data of wheat. Application of one-fourth nitrogen as basal and three-fourth at crown root initiation stage produced the maximum yield. Application of higher rate of nitrogen caused increased ammonia volatilization in sandy loam soil but not in clay loam soil. Application of urea mixed with oil cake of Citrullus colosynthis, a nitrification retarder, to a clay loam soil caused more ammonia volatilization than urea alone. Thus the advantage of ammonium conservation obtained through the use of nitrification retarder was counteracted by increased ammonia volatilization in alkaline soils.