Weather and soil in the US Midwest influence the effectiveness of single- and split-nitrogen applications in corn production

Authors: CLARK, JASON - South Dakota State University; FERNANDEZ, FABIAN - University Of Minnesota; CAMBERATO, JAMES - Purdue University; CARTER, PAUL - Retired ARS Employee; FERGUSON, RICHARD - University Of Nebraska; FRANZEN, DAVID - North Dakota State University; Kitchen, Newell; LABOSKI, CARRIE - University Of Wisconsin; NAFZIGER, EMERSON - University Of Illinois; SAWYER, JOHN - Iowa State University; SHANAHAN, JOHN - Fortigen

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2020
Publication Date: 10/29/2020
Citation: Clark, J.D., Fernandez, F.G., Camberato, J.J., Carter, P.R., Ferguson, R.B., Franzen, D.W., Kitchen, N.R., Laboski, C.A., Nafziger, E.D., Sawyer, J.E., Shanahan, J.F. 2020. Weather and soil in the US Midwest influence the effectiveness of single- and split-nitrogen applications in corn production. Agronomy Journal. 112(6):5288-5299. https://doi.org/10.1002/agj2.20446.
DOI: https://doi.org/10.1002/agj2.20446

Interpretive Summary: Nitrogen (N) is the essential nutrient that most often limits corn yield. The two main sources of N for corn are the decomposition of organic N in the soil into inorganic forms (N mineralization) and N from application of synthetic fertilizers. The difficulty in knowing how much N fertilizer to apply is that it is hard to predict the quantity of N that the process of mineralization will supply, as it can vary between 20 to 100% of the corn's N requirement. Results from a 49 site-year study across eight U.S. Midwestern states (North Dakota, Minnesota, Wisconsin, Nebraska, Iowa, Illinois, Indiana, and Missouri) were used to better understand the effectiveness of split (i.e., some N at planting and the majority as a sidedress) vs. single at-planting N applications for supplying crop N needs. In general, split N applications provided higher corn grain yield when consistent precipitation was available to incorporate fertilizer at the time of sidedress application. Split applications were also better in soils with greater potential for N loss early in the growing season (e.g., sandy soils). On the other hand, single N applications provided higher corn grain yield where precipitation was not reliably available to incorporate N fertilizer at the time of sidedress application. Further, single N applications provided higher corn grain yield in soils with greater potential for mineralization throughout the season and better nutrient and water retention capability, as indicated by greater silt and clay content. Overall, these results show that N application timing decisions should be made based on soil properties and weather conditions because they influence the effect of N timing on corn grain yield and post-harvest soil nitrate-N. These results benefit farmers as they seek ways to improve practices that match N fertilizer application amount and timing to crop N needs.

Technical Abstract: Splitting the N application into two or more timings may improve corn (Zea mays L.) grain yield and N recovery relative to a single-N application. A 49 site-year study across eight U.S. Midwestern states compared the effect of an at-planting (single-N application) and two split-N applications [45 (45+SD) or 90 kg N/ha (90+SD) at planting with the remainder of the total rate (180 or 270 kg N/ha) applied at V9]. For split-N applications, soil and plant responses were similar between 45+SD and 90+SD 93–98% of the time, indicating the at-planting N rate of 45 kg N/ha may be all that is needed in most cropping scenarios. Splitting the N application compared to a single-N application changed soil NO3–N at VT and post-harvest <35% of the time and plant N uptake and grain yield <15% of the time. Split-N applications had greater grain yield in areas with uniform precipitation around the sidedress timing (Shannon Diversity Index >0.56–0.59) to incorporate N in the root zone, and in coarse-textured soil (sand content >4–10%) that had greater potential for N loss. Single-N applications produced greater grain yield in soils with more total N (>2.1–2.4 g/kg) to support N mineralization and greater cation exchange capacity (CEC) (> 27–31 cmolc/kg), silt content (>66–74%), or clay content (>24–37%) to improve nutrient and water retention. Decisions on nitrogen application timing should be made based on soil parameters and typical weather conditions around the sidedress timing.