Combination of biological and chemical soil tests best predict maize nitrogen response

Abstract

Soil tests can help optimize nitrogen (N) fertilizer rates, thereby improving farmer profitability and environmental performance. In US Midwest maize (Zea mays) production, however, most soil N tests have limited accuracy to predict N fertilizer requirements. Here we tested the individual and combined ability of 30 soil tests (12 rapid N extractions, seven biological carbon or N tests, six long-term incubation kinetic parameters, and five other routine soil tests), as well as environmental and management data, to predict maize response to N fertilizer across 56 site-years in the US Midwest. Out of 30 soil tests, and across all site-years, a 14-d aerobic incubation best predicted whether maize responded to N fertilizer, and a 5-min tetraphenyl borate extraction best predicted agronomic optimum N rate. We combined these two tests to evaluate their ability to predict N fertilizer response against the most commonly used soil N test in the US Midwest, the pre-sidedress or late-spring nitrate test (PSNT or LSNT). The combination of soil tests nearly doubled the ability to predict nonresponsive sites compared to PSNT, and on average resulted in a 40% reduction in over-application and 37% reduction in under-application of N fertilizer. Weather and management variables marginally improved the prediction of maize N response.Our results indicate that a simple combination of biological N mineralization (14-d aerobic incubation) and chemical extraction (5-min tetraphenyl borate) assays could improve current N fertilizer recommendations.Abbreviations: AEIM, 14-day aerobic incubation with moist soils; AONR, agronomic optimum nitrogen rate; KCl8, 8-minute 2 M KCl extract for nitrate; LSNT, late-spring nitrate test; NRHY, maize nonresponsive to fertilizer nitrogen but high-yielding site-year; NRLY, maize nonresponsive to fertilizer nitrogen but low-yielding site-year; NUE, nitrogen use efficiency; PSNT, pre-sidedress nitrate test; RN, maize responds to nitrogen fertilizer; SOC, soil organic carbon; STK, Mehlich III extractable potassium; STP, Mehlich III extractable phosphorus; TPB5, 5-minute tetraphenyl borate extraction of ammonium.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Soil net nitrogen mineralization and leaching under Miscanthus × giganteus and Zea mays

“…We do know that cattle manure was applied for decades to the NW site (personal communication), which may have narrowed the soil C‐to‐N ratio compared to the Central site (10.8 vs. 13.2). Therefore, the legacy organic N input has likely created a strong “site effect” with high baseline N min rates and lower crop need for fertilizer N (Jokela, 1992; McDaniel et al, 2020; Tejera et al, 2019). Many studies show N fertilizer application accelerates N min in what has been called “SOM priming” (Fernández et al, 2017; Jenkinson et al, 1985; Lu et al, 2011); however, we found conflicting evidence of this effect.…”

Improving publicly available corn nitrogen rate recommendation tools with soil and weather measurements

“…Using proven ensemble learning methods, multiple weak predictors (i.e., tools, soil, weather) could be combined for a more accurate prediction of EONR. One example of ensemble learning that was successful at improving a few N recommendation tools was boosting (Bean et al., 2018; McDaniel et al., 2020; Ransom et al., 2019). Boosting works as a forward adaptative model, where an initial model is improved by fitting a new function to the residuals of the prediction (e.g., difference between tool's recommendations and EONR).…”

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

“…Potentially mineralizable N (PMN) is the inorganic N released during the incubation 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 McDaniel et al, 2020;Moore et al, 2019Yost et al, 2018).…”

“…The PMC was calculated by the cumulative CO 2 produced over the 14‐d incubation. The 14‐d length of the incubation is long enough to capture most of the change in CO 2 and a good measure of PMN (McDaniel et al., 2020).…”