Influence of Phosphorus Management on Potential for Soluble Phosphorus Loss through Leaching.

Phosphorus (P) is an essential nutrient for maximizing yield in corn (Zea mays L.) and soybean (Glycine Max L.) systems in Minnesota. The over application of P in agricultural systems may pose a threat to water quality due to the loss of dissolved P to fresh water bodies leading to eutrophication. The objectives of this study were to evaluate the potential for water soluble P loss from top soils (0-15 cm) across a range of initial soil test phosphorus (STP) levels, and to measure soluble P movement following surface application. Intact soil cores were collected from nine field sites throughout Minnesota and treated with soluble P fertilizer in the lab. Cores were then leached with deionized water at ten times field capacity for each corresponding soil type. Leaching events were staggered 0, 1, 3, and 7 days after fertilization for each soil type and initial STP level. Leachate was collected and analyzed for water extractable P (WEP) colorimetrically to approximate P loads. Timing of leaching event after fertilization significantly influenced the amount of WEP leached across all sites. After fertilization, the immediate (0 day) and 1 day leaching event P loads were significantly different from the 3 day and 7 day leach timing. Soil type may have affected P load levels as well, with sandy soils leaching less WEP than clays.