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

Authors: CLARK, JASON - South Dakota State University; FERNANDEZ, FABIAN - University Of Minnesota; Veum, Kristen; CAMBERATO, JAMES - Purdue University; CARTER, PAUL - Dupont Pioneer Hi-Bred; FERGUSON, RICHARD - University Of Nebraska; FRANZEN, DAVID - North Dakota State University; KAISER, DANIEL - University Of Minnesota; Kitchen, Newell; LABOSKI, CARRIE - University Of Wisconsin; NAFZIGER, EMERSON - University Of Illinois; ROSEN, CARL - University Of Minnesota; SAWYER, JOHN - Iowa State University; SHANAHAN, JOHN - Fortigen

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2020
Publication Date: 5/6/2020
Citation: Clark, J.D., Fernandez, F.G., Veum, K.S., Camberato, J.J., Carter, P.R., Ferguson, R.B., Franzen, D.W., Kaiser, D.E., Kitchen, N.R., Laboski, C.A., Nafziger, E.D., Rosen, C.J., Sawyer, J.E., Shanahan, J.F. 2020. Adjusting corn nitrogen management by including a mineralizable-nitrogen test with the preplant and presidedress nitrate tests. Agronomy Journal. 112(4):3050-3064. https://doi.org/10.1002/agj2.20228.
DOI: https://doi.org/10.1002/agj2.20228

Interpretive Summary: Improved prediction of corn production could provide economic benefits to producers. Laboratory soil tests such as nitrate, ammonium, and estimates of potentially mineralizable nitrogen (PMN), may help predict agronomic outcomes such as grain yield, N uptake, and N requirement. However, a full understanding of the utility of these soil tests is still lacking. In this study, the timing and depth of soil sampling were important and accounting for soil and weather characteristics improved agronomic predictions when using these tests. This study establishes that several factors need to be considered when using laboratory soil tests such as PMN to help make agronomic decisions for corn production. Ultimately, this information helps producers make crop management decisions for improved economic and environmental outcomes.

Technical Abstract: Anaerobic potentially mineralizable N (PMN) combined with the pre-plant (PPNT) or pre-sidedress (PSNT) nitrate tests may improve corn (Zea mays L.) production predictions. Forty-nine corn N response studies were conducted across the US Midwest to evaluate the capacity of the PPNT and PSNT to predict grain yield, N uptake, and economic optimal N rate (EONR) when adjusted by soil sampling depth, soil texture, temperature, PMN, and initial NH4–N from PMN analysis. Pre-plant soil samples were obtained for PPNT (0–30, 30–60, 60–90 cm) and PMN (0-30 cm) before N fertilization. In-season soil samples were obtained at the V5 corn development stage for the PSNT (0–30, 30–60 cm) at the 0 kg N ha-1 at-planting rate and for PMN when 0 and 180 kg N ha-1 was applied at-planting. Separating soils by texture or sites by growing degree days and including PMN and initial NH4–N with either NO3–N test best predicted grain yield, N uptake, and EONR. Using PSNT instead of PPNT normally increased predictability of corn agronomic variables by >11%. Response variable prediction when N fertilizer was not applied (grain yield and N uptake at zero-N) was 20% greater, on average than when N fertilizer was applied (EONR and grain yield at EONR). Although the predictability of grain yield, N uptake, and EONR increased by including PMN and initial NH4–N with PPNT or PSNT, these increases were insufficient to justify using PMN without NH4-N to improve N fertilizer management.