Adjusting corn nitrogen management by including a mineralizable‐nitrogen test with the preplant and presidedress nitrate tests

Jason D Clark,Newell R Kitchen,Richard B Ferguson,John F Shanahan,Carrie A M Laboski,James J Camberato,John E Sawyer,Emerson D Nafziger,Carl J Rosen,David W Franzen,Fabián G Fernández,Daniel E Kaiser,Kristen S Veum,Paul R Carter

doi:10.1002/agj2.20228

Abstract

AbstractThe anaerobic potentially mineralizable N (PMN) test combined with the preplant (PPNT) and presidedress (PSNT) nitrate tests may improve corn (Zea mays L.) N fertilization predictions. Forty‐nine corn N response experiments (mostly corn following soybean [Glycine max (L.) Merr.]) were conducted in the U.S. Midwest from 2014–2016 to evaluate the ability of the PPNT and PSNT to predict corn relative yield (RY) and N fertilizer over‐ and under‐application rates when adjusted by PMN. Before planting and N fertilization, PPNT (0–30, 30–60, and 60–90 cm) and PMN (0–30 cm) samples were obtained. In‐season soil samples were obtained at the V5 development stage for PSNT (0–30, 30–60 cm) in all N rate treatments and PMN (0–30 cm) in only the 0 and 180 kg N ha−1 preplant N treatments. Increasing NO3–N sampling depths beyond 30 cm with or without PMN improved RY predictability marginally (R2 increase up to 0.20) and reduced over‐ and under‐application frequencies up to 14%. Including PMN (preplant only) with PPNT or PSNT improved RY predictability minimally (R2 increase up to 0.10) only for coarse‐ and medium‐textured soils, but N fertilizer over‐ and under‐application frequencies were not substantially reduced (≤12%). These marginal improvements in RY predictability and N fertilizer over‐ and under‐application frequencies, regardless of the variables used (e.g., fertilization, sampling depth, soil texture, and growing degree‐day categories), demonstrate that including PMN with soil NO3–N alone does not improve corn N fertilization need predictions enough to recommend their use.

Highlights

Improving soil testing and the use of soil tests used in making management decisions can improve corn fertilizer-N rate guidelines (Dinnes et al, 2002)
Greater grain yield responses to N fertilizer for some of these categories may be the result of less N supplied to the corn crop from mineralization (Lory & Scharf, 2003), as N mineralization potential and soil organic matter concentration are related to soil texture and temperature (Cabrera, Kissel, & Vigil, 2005; Clark et al, 2019; Kuzyakova, Turyabahika, & Stahr, 2006)
Our study showed that grain yield response to N decreased as the mean potential for N mineralization (PMN) increased among categories within the textural and growing degree-days (GDD) groupings (Table 1)

Summary

Introduction

Improving soil testing and the use of soil tests used in making management decisions can improve corn fertilizer-N rate guidelines (Dinnes et al, 2002). The preplant (PPNT) and presidedress (PSNT) nitrate tests are commonly used to assess inorganic N, and the anaerobic potentially mineralizable N test (PMN) is commonly used to assess mineralizable N (Magdoff, Ross, & Amadon, 1984; Waring & Bremner, 1964). Using these soil tests together has the potential to improve fertilizer-N rate guidelines. The PPNT is taken early in the spring before any organic or inorganic N amendments are applied to the soil to measure the amount of NO3–N remaining in the soil from the previous season. The utility of these nitrate tests are judged on their capacity to correctly identify the CSNC and separate responsive and nonresponsive sites (Bundy, Walters, & Olness, 1999)

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