Effects of Urea‐Potassium Chloride and Nitrogen Transformations on Ammonia Volatilization from Urea

Abstract

AbstractAmmonia volatilization following fertilization with urea can be substantial. Losses via NH3 volatilization may be reduced with the concurrent application of KCl, which temporarily reduces soil pH. The objective of this study was to examine the influence of various urea‐KCl mixtures on NH3 volatilization and N transformations in two soils. Urea, granular urea plus KCl, urea plus KCl in solution, and urea coated with powdered KCl were added to a Matapeake silt loam (a fine‐loamy, mixed, mesic Typic Hapludult) and a Hagerstown silty clay loam (a fine, mixed, mesic Typic Hapludalf) at rates equivalent to 260 kg urea ha−1 (120 kg N ha−1) and 260 kg KCl ha−1 (135 kg K ha−1). During the first 13 d of incubation in the Matapeake soil, 26% of the N applied as urea alone was lost via NH3 volatilization. From the KCl‐coated urea, only 13% of the applied N was lost via volatilization. Ammonia losses from the Hagerstown soil were less than from the Matapeake soil but were still significantly reduced by the KCl coating on urea. Differences in NH3 volatilization between the soils were primarily attributed to the rate of urea hydrolysis and subsequent N transformations. These results indicate that coating urea with KCl may offer a significant advantage over uncoated urea, especially in K‐deficient soils.