Legacy effects of long-term nitrogen fertilizer application on the fate of nitrogen fertilizer inputs in continuous maize

Authors: POFFENBARGER, HANNA - Iowa State University; SAWYER, JOHN - Iowa State University; BARKER, DANIEL - Iowa State University; Olk, Daniel - Dan; SIX, JOHANN - Swiss Federal Institute Of Technology Zurich; CASTELLANO, MICHAEL - Iowa State University

Submitted to: Agriculture Ecosystems and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2018
Publication Date: 7/20/2018
Publication URL: https://handle.nal.usda.gov/10113/6101498
Citation: Poffenbarger, H.J., Sawyer, J.E., Barker, D., Olk, D.C., Six, J., Castellano, M.J. 2018. Legacy effects of long-term nitrogen fertilizer application on the fate of nitrogen fertilizer inputs in continuous maize. Agriculture Ecosystems and the Environment. 265:544-555. https://doi.org/10.1016/j.agee.2018.07.005.
DOI: https://doi.org/10.1016/j.agee.2018.07.005

Interpretive Summary: Nitrogen fertilizer is applied at significant rates to most crop lands. Understanding the factors of its availability to crops will help improve the efficiency of its application, so that grain yields can be maximized while minimizing environmental damage caused by over-application. In this study we found that corn grain yield responses to nitrogen fertilizer in research plots were affected by their previous history of nitrogen fertilizer application. These results are likely due to long-term changes in soil properties, including the amount of soil nitrogen, that were caused by the rates of previous nitrogen applications. These results can help explain why crop responses to nitrogen fertilizer vary among fields, and they show the additional benefits to soil properties of nitrogen fertilizer application. The results will be useful to agronomists, farmers, and other crop managers, and to researchers of soil nitrogen and fertilizer nitrogen.

Technical Abstract: Nitrogen fertilizer management can impact soil organic C (SOC) stocks in cereal-based cropping systems by regulating crop residue inputs and decomposition rates. However, the impact of long-term N management, and associated SOC changes, on crop N use efficiency is not well understood. Using two 15-year N fertilization experiments on continuous maize (Zea mays L.) in Iowa, which have generated gradients of SOC, we evaluated the legacy effects of N fertilizer inputs on N use efficiency of maize. We applied isotopically-labeled N fertilizer at the site-specific agronomic optimum rate across the historical N fertilizer gradient and measured fertilizer recovery in crop and soil pools. Crop recovery of fertilizer N at physiological maturity averaged 88 kg N ha-1 in central Iowa and 37 kg N ha-1 in southern Iowa (44% and 14% of fertilizer applied N, respectively). At both locations, crop fertilizer N recovery exhibited a curvilinear response to historical N rate, with 10%-30% greater recovery at the lowest and highest historical N rates than the intermediate ones. Decreasing crop recovery of fertilizer N from low to intermediate historical N rates corresponded to a decline in early-season fertilizer N retention in topsoil (0-15 cm) mineral-associated organic matter, while increasing crop recovery of fertilizer N from intermediate to high historical N rates corresponded to an increase in crop yield potential and early-season fertilizer N retention in topsoil particulate organic matter. Historical N rate had no effect on the fertilizer N recovery summed across crop aboveground biomass and all soil layers (0-120 cm). Our results suggest that long-term N applications increase SOC content in continuous maize systems, which in turn affects crop fertilizer N recovery efficiency by controlling early-season fertilizer retention in topsoil and enhancing crop yield potential.