Current turfgrass fertilizer recommendations do not account for plant‐available soil N mineralized from labile C fractions. The Solvita Soil CO2–Burst (SSCB) test can measure mineralizable C via soil CO2 respiration. This study was conducted across 3 yr (2014–2016) in Connecticut to determine: (i) if SSCB–C concentrations are correlated to responses from predominately Kentucky bluegrass (Poa pratensis L.) and tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] lawns, and (ii) the probability of turfgrass responses being equal to or greater than responses from common urea rates in relation to SSCB–C concentrations. Randomized complete block design field experiments were set out with 23 rates of organic fertilizer (0–2000 kg N ha−1 yr−1) and four different rates of urea (50, 100, 150, and 200 kg N ha−1 yr−1). Yearly spring soil samples were analyzed for SSCB–C concentrations and correlated with turfgrass responses. Growth and quality responded positively and linearly (P < 0.001) to SSCB–C concentrations, but variability was high and correlations were relatively weak. When spring soil SSCB–C concentrations were ≥91, 113, 166, and 211 mg kg−1, there was a ≥90% probability that overall combined responses across species and variables would be equal to or greater than responses obtained from urea rates of 50, 100, 150, and 200 kg N ha−1 yr−1, respectively. The SSCB test has promise for predicting the probability of soils supporting turfgrass whose performance equals or exceeds benchmark values. This would be helpful in guiding N fertilization, but high variability within the test may limit its predictive ability.

Core Ideas There are limited data to determine if the Illinois Soil Nitrogen Test and Solvita Labile Amino Nitrogen test are correlated. Across a 6‐yr study, Illinois Soil Nitrogen Test and Solvita Labile Amino Nitrogen were significantly and positively correlated. Illinois Soil Nitrogen Test and Solvita Labile Amino Nitrogen concentrations increased linearly across organic fertilizer rates. Illinois Soil Nitrogen Test concentrations increased at a greater rate than Solvita Labile Amino Nitrogen concentrations. The Solvita Labile Amino Nitrogen test may offer an easy and rapid soil analysis to guide N fertilization. The Illinois soil nitrogen (N) test (ISNT) and the Solvita Labile Amino‐Nitrogen (SLAN) test are chemical analyses that estimate the concentrations of soil labile N. The SLAN uses the same reagent as the ISNT but is a relatively new test with limited field data available. This study was conducted across 6 yr (2008–2013) to determine if concentrations of SLAN–N and ISNT–N are correlated in soils under predominantly Kentucky bluegrass (Poa pratensis L.) and tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] lawn turf and to compare the response of SLAN–N and ISNT–N concentrations in relation to varying organic fertilizer rates. Separate randomized complete block field experiments were established in Connecticut on the two species with varying rates of an organic fertilizer to create a wide range of labile soil N concentrations. Soil samples were collected in the spring of each year and analyzed for concentrations of ISNT–N and SLAN–N. For all years and each species, and for pooled years and species, SLAN–N concentrations were positively and significantly (P < 0.05) correlated with ISNT–N concentrations. Correlations were strongest (r > 0.80) at Year 6 of the study. Furthermore, SLAN–N and ISNT–N concentrations increased linearly (P < 0.05) in response to organic fertilizer rate, but the rate of change was greater for ISNT–N. The data suggest that the SLAN test is generally well correlated with the ISNT and may offer an easy and rapid soil analysis to guide N fertilization.

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Current turfgrass fertilizer recommendations do not account for potential mineralizable N in the soil. The Solvita Soil Labile Amino‐Nitrogen (SLAN) test measures a labile fraction of soil N. This study was conducted across 9 yr (2008–2016) in Connecticut to determine if responses from predominately Kentucky bluegrass (Poa pratensis L.) and tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] lawns are correlated to SLAN–N concentrations, and to determine the probability of turfgrass responses equaling or exceeding the response from benchmark urea rates in relation to SLAN–N concentrations. Randomized complete block design field experiments were set out with 23 rates of an organic fertilizer (0–2000 kg N ha−1 yr−1) and four different rates of urea (50, 100, 150, and 200 kg N ha−1 yr−1). Yearly spring soil samples were analyzed for SLAN–N concentrations, and turfgrass growth and quality responses were collected during the growing seasons. Turfgrass responded positively and linearly (P < 0.001) to SLAN–N concentrations, but correlations were relatively weak to moderate. When spring soil SLAN–N concentrations were ≥158, 165, 198, and 217 mg kg−1, there was a ≥90% probability that overall combined responses across species and measured variables would be equal to or greater than responses obtained from 50, 100, 150, and 200 kg urea N ha−1 yr−1, respectively. The SLAN test has promise as an objective soil test to categorize the N fertilization response potential of turfgrass soils, and this would be helpful in guiding N fertilization.