Guiding fall fertilization of cool‐season turfgrass lawns with verdure tissue‐N tests

Abstract

AbstractObjective tests are not widely used to guide fall N fertilization of turfgrasses, and N is applied at predetermined rates regardless of plant‐N status. This study was conducted across 3 yr in Connecticut to determine if fall verdure concentrations of total N, dry‐tissue extractable nitrate (NO3)–N, and fresh sap NO3–N could guide fall N fertilization for a mixed‐species, cool‐season turfgrass lawn. Field experiments were set out with varying fall N rates and verdure samples were collected weekly in October and November. Verdure tissue‐N test concentrations in response to N rates were analyzed with polynomial (quadratic or cubic) and linear‐response and plateau (LRP) models. Models were significant (P < .0001) for all tissue concentrations in response to N rates and estimates were comparable between models. When referenced to expected responses from the commonly recommended fall N rates of 24.5, 49, and 98 kg ha−1, there would be no need for N fertilizer when concentrations of fall verdure total N are ≥22, ≥25, and ≥30 g kg−1; dry‐tissue extractable NO3–N are ≥119, ≥193, and ≥840 mg kg−1; and fresh sap NO3–N are ≥94, ≥115, and ≥171 mg L−1, respectively. Variability of the verdure tissue‐N tests was no greater than most routine soil and tissue tests currently used to monitor nutrient status in turfgrasses. The results suggest that verdure tissue‐N tests have potential in guiding fall N fertilization of cool‐season turfgrass lawns.