Turfgrass Growth and Color Correlated to Spring Illinois Soil Nitrogen Test and Soil Permanganate‐Oxidizable Carbon Concentrations

Abstract

ABSTRACTThe Illinois soil nitrogen test (ISNT) and soil permanganate‐oxidizable C (POXC) concentrations have been used to estimate mineralization potential of agricultural soils, assess soil quality, distinguish differences between crop management treatments, and predict crop response to N fertilization. However, it is not known if these measures are correlated to growth and color quality responses of cool‐season turfgrasses. This study was conducted across 5 yr (2008–2012) in Connecticut to determine if a single spring measurement of Illinois soil nitrogen test‐N (ISNT‐N) and POXC concentrations could be used to estimate color and growth responses of Kentucky bluegrass (Poa pratensis L.) and tall fescue (Festuca arundinacea Schreb.) lawns. Randomized complete block field experiments were set out on the two species with varying rates of an organic fertilizer. Soil samples were collected in early May of each year and analyzed for concentrations of ISNT‐N and POXC. Turfgrass color, clippings yield, clippings total N concentration, and clippings total N uptake were measured from May through October. Turfgrass responses showed consistent positive linear responses (p < 0.05) as a function of ISNT‐N and POXC. Across species and years, ISNT‐N and POXC were generally greater under tall fescue than under Kentucky bluegrass. A single spring measurement of soil ISNT‐N and POXC shows promise in categorizing Kentucky bluegrass and tall fescues lawns as to their likelihood of N fertilization response. The data suggest a low probability of meaningful Kentucky bluegrass and tall fescues lawn responses to N fertilization when spring ISNT‐N and POXC concentrations exceed 250 mg kg−1 and 1300 mg kg−1, respectively.