Nitrate leaching in an Atlantic Coastal Plain soil amended with poultry manure or urea-ammonium nitrate: Influence of thiosulfate

Nitrate leaching, which can lead to groundwater contamination, is a common occurrence, especially in sandy, well drained soils. Nitrogen from poultry manure (PM) and ammonium fertilizers has been shown to undergo rapid nitrification upon addition to soils, making it highly susceptible to nitrate leaching. Any management technique that could delay nitrification and thereby reduce nitrate leaching would be desirable. Ammonium thiosulfate has been shown to be an effective nitrification inhibitor in laboratory studies and may be useful in reducing nitrate leaching. Soil columns, 75 cm long and inner diameter 19.6 cm, were packed with a reconstituted profile of a Rumford loamy sand and amended with urea-ammonium nitrate (UAN) or PM. Corn was grown in the columns to create a dynamic soil/plant system. Columns were placed in a greenhouse and were leached periodically for a period of 10 weeks with deionized water in amounts intended to simulate early spring and summer rainfall patterns in the Atlantic Coastal Plain. Column leachates, as well as plant and soil samples were collected and analyzed for NO₃-N and NH₄-N. Nitrate-N leaching was largely dependent upon the amount of water moving through the system. Ammonium thiosulfate did not significantly decrease NO₃-N leaching or increase plant N uptake when used in combination with UAN or PM. Comparable amounts of NO₃-N leaching were observed for the UAN and the PM treated column. Additionally, large amounts of NO₃-N leaching were observed with the control columns, suggesting that residual soil N from previous crops can contribute significantly to NO₃-N leaching and may deserve further investigation.