Potassium and Iron Fertilization Effects On Performance of Velvet Bentgrass Under Wear Stress.

Improved velvet bentgrass (VBG; Agrostis canina L.) cultivars exhibit excellent turf performance under wear compared with many creeping bentgrass (A. stolonifera L.) cultivars; however, there is a lack of research on the effects of fertility on VBG performance. The objective of this trial was to determine the effect of potassium and iron nutrition on the performance of velvet bentgrass subjected to foot traffic. A field trial was initiated in 2010 on a 6-yr-old ‘Greenwich’ VBG turf in North Brunswick, NJ. A 2x2x5 factorial arranged in a split-split plot design with three replications was used for this trial. The factor of foot traffic (none or 200 rounds per day) was applied as main plots. Sub-plots were the iron sulfate factor applied at 0 or 0.12 g m^-2 of Fe every two weeks.  Sub-sub-plots were the potassium sulfate factor applied at N:K of 1:0, 1:0.4, 1:0.8, 1:1.7, and 1:3.3 every two weeks. Nitrogen was applied biweekly at a rate of 4.9 kg ha^-1 As expected, foot traffic reduced turf quality and color compared to no foot traffic from June through October in 2010 and 2011, especially during high temperature stress.  Biweekly iron sulfate applications increased turf color throughout the growing season, but improvement in turf quality was much more subtle.  Biweekly applications of potassium sulfate at a N:K ratios of 1:1.7 and 1:3.3 lowered turf quality and color from July through October compared to the lower ratios or no application of potassium.  Our results indicate that biweekly applications iron sulfate can be used to mask discoloration of velvet bentgrass caused by foot traffic. Biweekly applications of K were detrimental at greater rates of K to turf performance.