Jason D. Clark https://orcid.org/0000-0001-7793-6411
Kristen S. Veum https://orcid.org/0000-0002-6492-913X
James J. Camberato https://orcid.org/0000-0002-6677-854X
David W. Franzen https://orcid.org/0000-0003-4862-8086
Daniel E. Kaiser https://orcid.org/0000-0002-8478-701X
Newell R. Kitchen https://orcid.org/0000-0002-8478-701X
John E. Sawyer https://orcid.org/0000-0003-4080-9616
Date of this Version
Agronomy Journal. 2020;112:3050–3064.
The 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 overand 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.