Multi-Year Effects of Foliar and Granular Nitrogen Fertilizers On Creeping Bentgrass Tissue and Soil Nutrient Concentrations.

Research on multi-year effects of foliar and granular nitrogen fertilizers alone or in combination on turfgrass tissue and soil nutrient concentrations is limited. The research objective was to determine the effect of foliar and granular nitrogen fertilizers on creeping bentgrass (Agrostis palustris Huds.) grown on three putting green rootzones. Research was initiated in 2009 at the Hancock Turfgrass Research Center at Michigan State University. Fertilizer treatments were urea, methylene urea, natural organic, foliar, foliar + granular, and an untreated control. Treatments were applied from May through October to Penn ‘A-4’ creeping bentgrass grown on three rootzones which were an 80:20 (sand:peat v/v) United States Golf Association mixture, an 80:10:10 (sand:peat:soil v/v) mix and a native sandy clay loam. Urea, methylene urea, and natural organic fertilizer treatments were applied at 24.4 kg N/ha/month. The foliar treatment was applied at two rates, 12.2 kg N/ha/month and 24.4 kg N/ha/month. The foliar + granular treatment consisted of a granular fertilizer application once a month at 12.2 kg N/ha/month and a foliar application twice a month at 6.1 kg N/ha/application. Soil samples to a 15 cm depth and tissue samples were collected in October 2009, and June and October 2010.  Soil samples were analyzed for macro-nutrients and tissue samples were analyzed for macro and micro-nutrients. Results indicate that fertilizer treatments resulted in higher N, P, and K tissue levels than the untreated control for October 2009 and 2010 samplings. However, the untreated control had higher tissue Ca, Mg, Mn, and Fe levels than the fertilized treatments. Among rootzones, higher soil N, P, and K values did not result in higher tissue N, P, and K values. After two years, there was no significant decrease in soil nutrient values for the foliar alone treatments, with the exception of nitrate-N which decreased from October 2009 to 2010.