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Soil sample timing, nitrogen fertilization, and incubation length influence anaerobic potentially mineralizable nitrogen

Jason D. Clark, Kristen S. Veum, Fabián G. Fernández, Newell R. Kitchen, James J. Camberato, Paul R. Carter, Richard B. Ferguson, David W. Franzen, Daniel E. Kaiser, Carrie A. M. Laboski, Emerson D. Nafziger, Carl J. Rosen, John E. Sawyer, John F. Shanahan
Soil Science Society of America journal 2020 v.84 no.2 pp. 627-637
Zea mays, application timing, atmospheric precipitation, carbon nitrogen ratio, clay fraction, corn, edaphic factors, fertilizer rates, field experimentation, heat sums, mineralization, nitrogen, nitrogen fertilizers, nutrient use efficiency, preplanting treatment, soil fertility, soil sampling, Midwestern United States
Understanding the variables that affect the anaerobic potentially mineralizable N (PMNₐₙ) test should lead to a standard procedure of sample collection and incubation length, improving PMNₐₙ as a tool in corn (Zea mays L.) N management. We evaluated the effect of soil sample timing (preplant and V5 corn development stage [V5]), N fertilization (0 and 180 kg ha⁻¹) and incubation length (7, 14, and 28 d) on PMNₐₙ (0–30 cm) across a range of soil properties and weather conditions. Soil sample timing, N fertilization, and incubation length affected PMNₐₙ differently based on soil and weather conditions. Preplant vs. V5 PMNₐₙ tended to be greater at sites that received < 183 mm of precipitation or < 359 growing degree‐days (GDD) between preplant and V5, or had soil C/N ratios > 9.7:1; otherwise, V5 PMNₐₙ tended to be greater than preplant PMNₐₙ. The PMNₐₙ tended to be greater in unfertilized vs. fertilized soil in sites with clay content > 9.5%, total C < 24.2 g kg⁻¹, soil organic matter (SOM) < 3.9 g kg⁻¹, or C to N ratios < 11.0:1; otherwise, PMNₐₙ tended to be greater in fertilized vs. unfertilized soil. Longer incubation lengths increased PMNₐₙ at all sites regardless of sampling methods. Since PMNₐₙ is sensitive to many factors (sample timing, N fertilization, incubation length, soil properties, and weather conditions), it is important to follow a consistent protocol to compare PMNₐₙ among sites and potentially use PMNₐₙ to improve corn N management.