Palmero, Francisco2024-11-072024https://hdl.handle.net/2097/44677Over the past 80 years, advances in plant breeding and crop management have increased maize (Zea mays L.) grain yield. However, this increase in maize productivity is linked to a high use of and dependency on nitrogen (N) fertilizers. The high use of N fertilizers can have undesirable environmental consequences. Therefore, improving the effective use of N in maize is critical to reduce its environmental footprint while achieving food security in a climate change context. This dissertation is organized into five chapters (Chapter 1, Introduction, and Chapter 5, Conclusions) addressing plant breeding and management strategies to improve the effective use of N in maize and its productivity. Through four field trials across two locations and four years, Chapters 2 and 3 advance our understanding of how biotechnology-based plant breeding modified carbon (C) and N dynamics in maize. In Chapter 2, we show the effect of extending the expression of a maize MADS-box transcription factor (ZmGos2-zmm28, event DP202216, Corteva Agrisciences) on key physiological and morphological traits associated with C-N dynamics in this crop. We found that the DP202216 trait increased C and N allocation to the grains. These increases were supported by higher accumulation of N in leaves and water-soluble carbohydrates in stems before flowering, along with an improved remobilization after flowering. In Chapter 3, we identify changes in the maximum limit of C and N partitioning to the grains in DP202216 maize hybrids at equal plant growth levels. We also determine the main factors underpinning the mechanisms associated with each observed change in C and N partitioning to grains. The DP202216 plants showed an increase in the upper boundary of C and N allocation to reproductive organs. We showed that this increase in C and N allocation was related to a higher ‘relative’ C and N demand by the grains in the DP202216 hybrids. Finally, in Chapter 4, we analyze different cases of N fertilizer reduction in maize across the United States Corn Belt, considering the uncertainty of "optimal" N rates. We also economically quantify the environmental cost savings to society under the most feasible N rate reduction case. We show that it is feasible to reduce the N fertilizer application while maintaining maize grain yield. This resulted in an increase in farmers’ profit while reducing the environmental costs of the N fertilization practices to society. Taken together, the findings reported in this thesis characterize exciting novel genetic variation for improved N utilization, combined with a practical management tool that could encourage growers to better manage N applications for optimum efficiency in maize production.en-USCornHarvest indexNitrogen harvest indexSustainabilityDissertation