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 co mmon occurrence, especially in sandy, well drained soils. Nitrogen fro m poultry manure (PM) and ammonium fertilizers has been shown to under go rapid nitrification upon addition to soils, making it highly suscep tible to nitrate leaching. Any management technique that could delay n itrification and thereby reduce nitrate leaching would be desirable. A mmonium thiosulfate has been shown to be an effective nitrification in hibitor in laboratory studies and may be useful in reducing nitrate le aching. Soil columns, 75 cm long and inner diameter 19.6 cm, were pack ed with a reconstituted profile of a Rumford loamy sand and amended wi th urea-ammonium nitrate (UAN) or PM. Corn was grown in the columns to create a dynamic soil/plant system. Columns were placed in a greenhou se and were leached periodically for a period of 10 weeks with deioniz ed water in amounts intended to simulate early spring and summer rainf all patterns in the Atlantic Coastal Plain. Column leachates, as well as plant and soil samples were collected and analyzed for NO3-N and NH 4-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 combi nation with UAN or PM. Comparable amounts of NO3-N leaching were obser ved 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.