N Fertilization Guidelines for Penn A4 Putting Greens: Because Rate, Form, and Timing Matter.

Granted N requirements of any turfgrass system are influenced by both temperature and labile organic matter fraction of the underlying soil, variation in shoot density and heat-tolerance traits across cultivars may deserve similar consideration. Relatively greater N requirements of densely-statured and heat-tolerant creeping bentgrass cultivars appear evidenced by recent accounts of their susceptibility to low-N diseases. Regardless, N deliveries at what have been referred to as ‘industry standard’ rates are unfounded and routinely inadequate. Monthly N recommendations for creeping bentgrass putting greens (PGs) in the range of 15-49 kg N ha^–1 continue to persist through 30 years of literature. Field experiments investigated N fertility programs of creeping bentgrass (Agrostis stolonifera L. ‘Penn A-4’) managed as PGs. Either sand- or soil-based PGs were treated with foliarly-applied, soluble N-forms at 0, 20, 30, or 40 kg (ha mo)^–1, every 6 or 12 d. Turfgrass canopy color, canopy density, clipping yield, tissue nutrient levels, root length density, and root mass were measured to evaluate turfgrass growth, health, and nutrient partitioning. Results indicate rootzone soil pH and alkaline inputs are important criteria to be used in N-form selection. More frequent fertilizer applications (at lesser rates) resulted in more consistent Penn A-4 shoot/root growth response.