Predicting Cool‐Season Turfgrass Response with Solvita Soil Tests, Part 2: CO₂–Burst Carbon Concentrations

Abstract

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.

Agroecosystem management responses to Haney soil health test in the southeastern United States

“…The lack of strong and consistent response of Nmin could also be attributed to its estimation from biological indicators in HSHT (Solvita CO 2 -C, WEOC, and WEON), which also showed a generally poor response to management differences (Tables 2-4). Other studies also reported a lack of strong response of Nmin estimated from HSHT parameters to agromanagement practices (Castro Bustamante & Hartz, 2016;Dick & Culman, 2016;Tu, 2016;Moore, Guillard, Morris, & Brinton, 2019). In addition, some studies discussed the limited applicability of using Nmin in predicting crop N fertilizer requirement due to the requirement of advanced yield estimation, high measurement variability of HSHT indicators, and region-specific calibration and validation of such pre-dictions (Norris, Chim, Evanylo, Reiter, & Thomason, 2018;Stahl, Fernández, & Kaiser, 2016).…”

Evaluation of humic fertilizers on a sand‐based creeping bentgrass putting green

“…(2019a) reported that PMC increased with increasing N rates. The varying results in PMC response to N fertilizer may be a result of N rates, in which higher N (100–257 kg N ha −1 ) amounts decrease PMC, whereas small N (12.5–50 kg N ha −1 ) additions may increase PMC (Grandy et al., 2013; Moore et al., 2019b). There was a nonsignificant trend for treatments with higher PMC to exhibit better turfgrass quality.…”

“…Potentially mineralizable N (PMN) is the inorganic N released during the incubation (Franzluebbers et al., 2018; McDaniel & Grandy, 2016). Both PMC and PMN can be an indicator of soil N‐supplying power, as has been shown with maize and turfgrass N response studies in the United States (Franzluebbers et al., 2018; McDaniel et al., 2020; Moore et al., 2019, 2019ab; Yost et al., 2018).…”

Guiding fall fertilization of cool‐season turfgrass lawns with NDVI sufficiency index

“…The SI measurements provide an objective measure of plant‐N status for turfgrass lawns, whereas the current practice of using predetermined N rates do not. A routine fall application of N at the currently recommended rates without adjusting for plant‐N status before fertilization will most likely increase the chance of excess N and increase leaching losses especially when soil mineralization potential is high (Miltner, Stahnke, & Backman, 2001; Moore et al., 2019; Yao et al., 2009) and/or if there is N carryover from previous fertilizer applications (Waddington et al., 1976). Therefore, measuring the reflectance SI of cool‐season turfgrasses during the fall to determine plant‐N status should provide more accurate guidance for N fertilization and protection against excess fertilizer N applications.…”

“…A commonly used spectral measurement in turfgrass research to determine treatment differences is the normalized difference vegetative index (NDVI). There are numerous citations in the turfgrass literature reporting significant relationships between NDVI or other spectral‐reflectance signals with N fertilization (reviewed in Bell, Kruse, & Krum, 2013; Catureglia et al., 2015, 2016; Caturegli et al., 2020; Geng, Guillard, Mangiafico, & Morris, 2014; Geng, Guillard, & Morris, 2014; Guillard, Fitzpatrick, & Burdett, 2016; Inguagiato & Guillard, 2016; Moore et al., 2019; Moore, Guillard, Morris, & Brinton, 2019; Obear, Kreuser, Hubbard, DeBels, & Soldat, 2017). However, relationships between reflectance signals and the response of turfgrass to N fertilization have not been analyzed with the objective to create site‐specific fertilizer recommendations.…”