A new perspective when examining maize fertilizer nitrogen use efficiency, incrementally

• Published in: PloS one 2022-05, Vol.17 (5), p.e0267215-e0267215
• Main Authors: Kitchen, Newell R, Ransom, Curtis J, Schepers, James S, Hatfield, Jerry L, Massey, Raymond, Drummond, Scott T
• Format: Article
• Language: English
• Subjects: Agricultural production; Agriculture - methods; Biology and Life Sciences; Corn; Crop yield; Crops; Datasets; Denitrification; Earth Sciences; Edible Grain - chemistry; Efficiency; Empirical analysis; Environmental risk; Fertilization; Fertilizers; Fertilizers - analysis; Grain; Growing season; Irrigation; Management tools; Mineralization; Nitrogen; Nitrogen - analysis; Optimal yield; Organic matter; Organic soils; Precipitation; Public policy; Rain; Rainfall; Research and Analysis Methods; Soil; Soil organic matter; Soils; Zea mays
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0267215

For maize (Zea mays L.), nitrogen (N) fertilizer use is often summarized from field to global scales using average N use efficiency (NUE). But expressing NUE as averages is misleading because grain increase to added N diminishes near optimal yield. Thus, environmental risks increase as economic benefits decrease. Here, we use empirical datasets obtained in North America of maize grain yield response to N fertilizer (n = 189) to create and interpret incremental NUE (iNUE), or the change in NUE with change in N fertilization. We show for those last units of N applied to reach economic optimal N rate (EONR) iNUE for N removed with the grain is only about 6%. Conversely stated, for those last units of N applied over 90% is either lost to the environment during the growing season, remains as inorganic soil N that too may be lost after the growing season, or has been captured within maize stover and roots or soil organic matter pools. Results also showed iNUE decrease averaged 0.63% for medium-textured soils and 0.37% for fine-textured soils, attributable to fine-textured soils being more predisposed to denitrification and/or lower mineralization. Further analysis demonstrated the critical nature growing season water amount and distribution has on iNUE. Conditions with too much rainfall and/or uneven rainfall produced low iNUE. Producers realize this from experience, and it is uncertain weather that largely drives insurance fertilizer additions. Nitrogen fertilization creating low iNUE is environmentally problematic. Our results show that with modest sub-EONR fertilization and minor forgone profit, average NUE improvements of ~10% can be realized. Further, examining iNUE creates unique perspective and ideas for how to improve N fertilizer management tools, educational programs, and public policies and regulations.