United States Midwest soil and weather conditions influence anaerobic potentially mineralizable nitrogen

Authors: CLARK, J - South Dakota State University; Veum, Kristen; FERNANDEZ, F - University Of Minnesota; CAMBERATO, J - Purdue University; CARTER, P - Dupont Pioneer Hi-Bred; FERGUSON, R - University Of Nebraska; FRANZEN, D - North Dakota State University; KAISER, D - University Of Minnesota; Kitchen, Newell; LOBOSKI, C - University Of Wisconsin; NAFZIGER, E - University Of Illinois; ROSEN, C - University Of Minnesota; SAWYER, J - Iowa State University; SHANAHAN, J - Farmer

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/8/2019
Publication Date: 9/5/2019
Citation: Clark, J.D., Veum, K.S., Fernandez, F.G., Camberato, J.J., Carter, P.R., Ferguson, R.B., Franzen, D.W., Kaiser, D.E., Kitchen, N.R., Loboski, C.A., Nafziger, E.D., Rosen, C.J., Sawyer, J.E., Shanahan, J.F. 2019. United States Midwest soil and weather conditions influence anaerobic potentially mineralizable nitrogen. Soil Science Society of America Journal. 83(4):1137-1147. https://doi.org/10.2136/sssaj2019.02.0047.
DOI: https://doi.org/10.2136/sssaj2019.02.0047

Interpretive Summary: Soil organic nitrogen can contribute significant portions of the nitrogen a crop needs during the growing season for optimal yield. Laboratory tests that incubate the soil under certain controlled conditions have been designed to estimate this contribution. These test measurements are referred to as potentially mineralizable nitrogen (PMN), and their results could be used by farmers to improve nitrogen management decisions for grain crops. However, the role that variations in soil properties (e.g., texture, organic matter) and weather conditions (e.g., precipitation amount and distribution, temperature) for altering PMN is not well understood. In this study, a range of climate and soil conditions were used to predict PMN from 32 sites located across eight US Midwestern states. The distribution of rainfall, warmer temperatures early in the season, and soil characteristics related to organic matter all demonstrated positive relationships with PMN. Even though soil and weather conditions were important for predicting PMN, other factors such as timing of soil sampling, fertilization practices, and laboratory methods also influenced PMN. Overall, this study provides information to improve soil testing tools that will benefit producers by improving prediction of nitrogen requirements, increase nitrogen use efficiency in corn, and enhance environmental protection.

Technical Abstract: Nitrogen provided to crops through mineralization is an important factor in N management guidelines. Understanding the interactive effects of soil and weather conditions on N mineralization needs to be improved. Thirty-two field studies were conducted across the US Midwest to determine the effect and predictability of soil and weather information on anaerobic potentially mineralizable N (PMNan) from various conditions. Soil was sampled (0-30 cm) for PMNan analysis before pre-plant N application (PP0N) and at the V5 development stage from the pre-plant zero (V50N) and 180 kg-N ha-1 (V5180N) rates and incubated for 7-, 14-, and 28-d. Even distribution of precipitation and warmer temperatures before soil sampling and greater soil organic matter (SOM) increased PMNan. Soil properties, including total C, SOM, and total N had the strongest relationships with PMNan (R2 = 0.40) followed by temperature (R2 = 0.20) and precipitation (R2 = 0.18) variables. The strength of the relationships between soil properties and PMNan from PP0N, V50N, and V5180N varied by = 10%. Including soil and weather in the model greatly increased PMNan predictability (R2 = 0.69), demonstrating the interactive effect of soil and weather on N mineralization at different times during the growing season regardless of N fertilization. Delayed soil sampling (V50N) and sampling after fertilization (V5180N) reduced PMNan predictability. However, longer PMNan incubations improved PMNan predictability of both V5 soil samplings closer to PMNan from PP0N, indicating the potential of PMNan from longer incubations providing improved estimates of N mineralization when N fertilizer is applied.