Bentgrass Cultivar and Annual Nitrogen Regime Affects Seasonal Shoot Density

Abstract

Creeping bentgrass (Agrostis stolonifera var. palustris Huds. Farw.) is the preferred turfgrass species for golf greens. During summer months, however, shoot density (SD) often declines, resulting in poor stand quality. Turf managers utilize several management practices to maintain turf vigor. One practice is light, frequent N fertilization. However, annual N rates vary widely. Recently, high shoot density (HSD) bentgrasses bred to provide superior appearance and stress tolerance compared to the industry standard, ‘Penncross,’ have been widely planted. The effect of variable N rates on these cultivars is unclear. This field study measured seasonal SD changes of three contrasting cultivars maintained with low and high N regimes, 112 and 196 kg of N per ha/year, respectively. Significant seasonal SD differences were measured and cultivars ranked ‘A-4’ (1400 to 2160 shoots/dm2) > ‘L-93’ (1230 to 1780 shoots/dm2) > ‘Penncross’ (760 to 1470 shoots/dm2). Generally, increasing N resulted in only slight differences in SD. In August, however, when N regime was averaged across cultivars, higher N significantly increased SD in both study years. For the densest, most persistent turf during summer months, a HSD cultivar should be planted and moderate N should be applied to sustain appearance and ensure adequate recovery should turf damage occur.