Surface Runoff Losses of Fertilizer Elements1
- Edward P. Dunigan,
- Robert A. Phelan and
- C. L. Mondart2
Surface runoff losses of fertilizer N, P, and K were measured from a Loring silt loam soil with an average slope of 5%. Plots seeded to pearl millet (Pennisetum typhoides [Burm.]) in 1973 and 1974 were fertilized at the rate of 112-49-93 kg/ha of incorporated N, P, and K using two different fertilizer blends, a 33.3-8.7-16.6 and an 8-3.5-6.6. The percent of water-soluble fertilizer elements lost in 1973 from the higher and lower blend concentrations, respectively, were N, 0.50 and 0.30%; P, 0.14 and 0.06%; and K, 0.67 and 0.92%. In 1974, N losses were 0.89 and 0.41%; P, 0.35 and 0.20%; and K, 0.42 and 0.35%. Precipitation during the experimental periods was 20.40 cm in 1973 and 11.03 cm in 1974. Two of the millet plots were then topdressed with NH4NO3 fertilizer at the rate of 112 kg N/ha. Topdressed fertilizer-N losses were 2.68% in 1973 and 1.82% in 1974. Precipitation during these second tests was 27.97 cm in 1973 and 27.69 cm in 1974. Ryegrass (Lolium multiflorum L.) plots were fertilized with sulfur-coated urea (SCU) and uncoated urea (U) at the rate of 224 kg N/ha during the growing seasons of 1973 and 1974. Total N losses (U vs. SCU) were 9.52 and 0.26% in 1973, and 1.67 and 0.42% in 1974. Precipitation was 23.89 cm in 1973 and 29.57 cm in 1974. A 10.08-cm rainfall on the third day of the test in 1973 caused almost three-fourths of the 9.52% N lost from the uncoated urea to be lost in that runoff and while it was still in the urea form. The sulfur coating prevented large surface losses of N from the SCU.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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