Nitrogen Effects On Quality of Velvet Bentgrass Grown On Sand and Soil Putting Greens.

Nitrogen source and rate effects on velvet bentgrass (Agrostis canina L.; VBG) putting greens are not well documented, particularly in the Midwest portion of the USA. Anecdotal claims state that fertilizers with greater acidifying effects provide better VBG quality than less acidic fertilizers. We wanted to determine the agronomic effects from fertilizers representing a range of acidity and N rates (49, 146, 244 kg ha^-1 yr^-1). Turf quality was rated on a 1 to 9 scale, with a 5.5 rating considered acceptable. Fertilizer treatments were applied at two week intervals, beginning June 2007, to one-year old ‘Vesper’ putting greens in Verona, WI, using liquid forms of ammonium sulfate, urea, ammonium nitrate and calcium nitrate. Root zones consisted of an 80:20 sand:peat mixture (pH 7.8) and a Troxel silt loam (fine-silty, mixed, superactive, mesic Pachic Argiudoll, with pH 7.0). In 2007, fertilizer type interacted with rate on the sand root zone with urea and ammonium nitrate applied at 244 kg N ha^-1 yr^-1 yielding acceptable turfgrass quality. In 2008, fertilizer type rarely affected turf quality in 2008.  Turf quality responded in a non-linear fashion to N rate on sand, with the most dramatic response between 49 and 146 kg N ha^-1 yr^-1. On soil, N rate had a more linear response. A minimum of 146 kg N ha^-1 yr^-1 was required for acceptable turf quality on soil, while the sand root zone would need greater than 244 kg N ha^-1 yr^-1.