Ammonia Volatilization from Lime Urea Ammonium Nitrate Suspensions Before and After Soil Application
1981
Winter, K. T. | Whitney, D. A. | Kissel, D. E. | Ferguson, R. B.
Limestone suspensions provide a means of uniformly applying finely divided liming materials to raise soil pH. Water has usually been the suspending medium, but N fertilizer solutions may be used. The objective of this research was to measure ammonia (NH₃) losses that might occur while a lime and urea-ammonium nitrate (UAN) suspension is being prepared and potential losses after the suspension is applied to soil. Ammonia volatilization was measured in the laboratory from lime-UAN suspensions formulated with lime sources containing various amounts of CaO. Suspension pH's, rates of loss, and total NH₃ losses were directly proportional to the CaO content of the lime material and ranged up to approximately 90% of the ammoniacal fraction of the UAN after 4 hours. Losses were not influenced greatly by the initial pH of the UAN materials used in the study. Ammonia volatilization from the surface of two acid soils was also measured after lime-UAN suspensions were applied at a rate of 840 kg/ha effective calcium carbonate [CaCO₃; (ECC)] and 112 kg N/ha. Lime applied with the UAN increased NH₃ volatilization, but less on Grundy sicl (Aquic Argiudoli) than on Parsons sil (Mollic Albaqualf) with a lower cation exchange capacity (CEC). Up to 17% of total N was lost with the lime-UAN treatments on Parsons soil with a CEC of 10.2. Results indicate substantial losses of NH₃ may occur while lime-UAN suspensions are being prepared only if the lime contains CaO. After soil application, NH₃ losses can occur in the absence of CaO if the lime-UAN is allowed to remain on the soil surface.
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