Russell Yarnell, M.S.
Education: Bachelor of Science in civil engineering (May 2004)
Master of Science in civil engineering from Kansas State University
McNair Project: Determining Runoff Concentrations of N and P from Urban Lawns (2003)
Mentor: Philip Barnes, Ph.D.
Fertilization of lawns places tons of nitrogen and phosphorus on the earth's surface, making it susceptible to runoff. Environmental concerns arise when nitrogen and phosphorus concentrations in streams and lakes promote rapid growth of plants, disturbing the natural ecology. Determining parameters that contribute to nutrient loss is important. The study investigated the correlation between soil moisture and nutrient losses in runoff. A 9.1 m x 18.3 m area was prepared with Kentucky bluegrass. Nine random plots, 1.5 m x 1.5 m (5 ft. x 5 ft.) consisted of three soil moistures: dry, normal, or moist. After achieving proper soil moisture, fertilizer was applied and then simulated rainfall proceeded. Two series of tests used 10-10-10 concentrations, one with dry granules, and the other using liquid formulation. The simulator provided an intensity of 5 cm hr-1 (2 in hr-1) for 1 hour. Analyzing nutrient concentrations in runoff samples showed significance in ammonium and phosphorus for dry soil conditions. Nitrates showed no significance for dry fertilizer. Phosphorus losses with the dry fertilizer ranged 2.96% to 6.50% while the nitrogen losses ranged 2.25% to 4.09%. For the liquid fertilizer, phosphorus, ammonium, and nitrate all showed significant difference for the moist plots. Phosphorus also showed significance between all three ranges of soil moisture. In the plots fertilized with a liquid formulation, phosphorus losses ranged 1.20% to 16.52% and nitrogen losses ranged 0.73% to 11.55%. From the observed results, allowing the soil to dry before fertilization will reduce the nutrient loss in runoff.