Multi-Year Effects of Foliar and Granular Nitrogen Fertilizers On Creeping Bentgrass Quality, Ball Roll Distance, and Dollar Spot and Worm Casting Occurrences.

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. All treatments were applied from May through October to Penn ‘A-4’ creeping bentgrass grown on three rootzones which were a an 80:20 (sand:peat v/v) United States Golf Association (USGA) mixture, an 80:10:10 (sand:peat:soilv/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. Turfgrass color, quality and chlorophyll ratings were measured weekly in 2009 and 2010. Ball roll distance was measured in July and August in 2010 using a Pelzmeter. Dollar spot (Sclerotinia homeocarpa) and worm casting mounds were counted when present. Results indicate urea, methylene urea, and natural organic treatments had the highest turfgrass color, quality, and chlorophyll ratings in May and June. In July, August, and September, foliar treatments  resulted in the highest color, quality, and chlorophyll ratings. After two years of fertilizer treatments, the natural organic treatment had the shortest ball roll distance compared with other treatments, and the untreated control had the longest ball roll distance. The USGA and 80-10-10 rootzones had longer ball roll distances than the native soil rootzone. Among the rootzones, the native soil had the most worm castings and least amount of dollar spot. The untreated control and the low rate foliar treatment had the least amount of dollar spot, but the most worm castings among fertilizer treatments.