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

Nitrogen provided to crops through mineralization is an important factor in N management guidelines. Understanding of the interactive effects of soil and weather conditions on N mineralization needs to be improved. Relationships between anaerobic potentially mineralizable N (PMN_an) and soil and weather conditions were evaluated under the contrasting climates of eight US Midwestern states. Soil was sampled (0-30 cm) for PMN_an analysis before pre-plant N application (PP0N) and at the V5 development stage from the pre-plant 0 (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 PMN_an. Soil properties, including total C, SOM, and total N, had the strongest relationships with PMN_an (R2 ≤ 0.40), followed by temperature (R² ≤ 0.20) and precipitation (R2 ≤ 0.18) variables. The strength of the relationships between soil properties and PMN_an from PP_0N, V5_0N, and V5_180N varied by ≤10%. Including soil and weather in the model greatly increased PMN_an 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 (V5_0N) and sampling after fertilization (V5_180N) reduced PMN_an predictability. However, longer PMN_an incubations improved PMN_an predictability from both V5 soil samplings closer to the PMN_an predictability from PP0N, indicating the potential of PMN_an from longer incubations to provide improved estimates of N mineralization when N fertilizer is applied.