Ammonia Volatilization from Surface Applications of Ammonium Compounds on Calcareous Soils: V. Soil Water Content and Method of Nitrogen Application

Ammonia‐nitrogen losses from soils were dependent on the existence of sufficient water for solubilization of the applied NH 4 ‐compounds. Laboratory data revealed that NH 3 volatilization from (NH 4 ) 2 SO 4 was greatly reduced on soils with 55% water at 12, 22 and 30°C as compared to soils with 30% water. Ammonia‐nitrogen losses were the highest at all temperatures and nitrogen applicatin rates when soils contained 13 to 30% soil water. Dry NH 4 ‐chemicals did not dissolve in soils with 0 and 8% soil water, therefore, little NH 3 was lost. Application of a concentrated (NH 4 ) 2 SO 4 solution to soils with 8% water resulted in near maximum NH 3 loss. This same solution, when applied to the surface of an oven dry soil, resulted in lower losses. Application of NH 4 NO 3 to soils with 55 water resulted in lower NH 3 losses when compared to soils with 8 to 30% water. Soils with 0% water retained essentially all applied NH 4 + ‐N whether applied in dry or concentrated liquid form. Apparent nitrogen recovery with barley ( Hordeum vulgare L., cv. Griggs) in a greenhouse experiment corresponded well to nonvolatilized NH 4 + determined in the laboratory. All nitrogen compounds were on the soil surface 7 days before application of irrigation water. Nitrogen uptake by barley was greatest when the material was applied as a dry salt to the surface of an air dry soil, intermediate when added as a dry salt to the surface of a recently saturated soil, and lowest when added as a solution to the surface of an air dry soil. Urea, urea + NH 4 H 2 PO 4 , and NH 4 NO 3 were exceptions. These compounds resulted in equal plant nitrogen absorption whether applied as a dry salt or as an aqueous solution to the surface of an air dry soil. Plant absorption of nitrogen from soil with these same N‐compounds, however, was greatest when applied to the surface of a soil saturated with water.