Assessing nutrient management strategies on agroecosystem productivity and sustainability in the U.S. Midwest

This dissertation addresses critical challenges in nutrient management within the U.S. Midwest, a region central to global corn production but increasingly vulnerable to environmental and sustainability issues. The research focuses on two key questions: (1) How do environmental factors and nutrient management practices, particularly nitrogen (N) strategies, affect crop productivity and sustainability? (2) How can nutrients be managed to balance productivity and environmental outcomes? Grounded in process-based ecosystem modeling and supported by extensive in-situ and regional-scale analyses, this work enhances understanding of N dynamics and informs the development of sustainable nutrient management strategies. The dissertation investigates the interactions between environmental conditions and different nutrient management practices on crop yields, and environmental impacts. Chapter 2 quantifies the effects of pre-growing-season precipitation and temperature on N availability and corn productivity, providing insights into optimizing fertilizer use under varying climatic conditions. Chapter 3 explores the agronomic and environmental trade-offs of soybean-corn versus continuous-corn rotations, revealing the mechanisms through which rotations influence soil organic carbon (SOC), N cycling, and economic returns. Chapter 4 evaluates the impacts of various N management strategies, including nitrification inhibitors, on productivity and sustainability, introducing novel metrics such as carbon intensity (CI) and economic margins to guide decision-making. Expanding to regional-scale analyses, Chapter 5 leverages a Model-Data Fusion (MDF) approach to integrate remote sensing-derived gross primary productivity (GPP) and crop yield data, enhancing the accuracy of ecosystem models in predicting spatial-temporal variations in the impacts of N practices. Chapter 6 summarized our work on developing advanced tools for nutrient management, including an enhanced Maximum Return to Nitrogen (MRTN) tool that incorporates environmental loss metrics and a new framework for phosphorus (P) and potassium (K) management. These tools provide data-driven, region-specific recommendations to improve nutrient use efficiency, reduce environmental harm, and sustain productivity. Overall, this dissertation advances agroecosystem modeling, bridges economic and environmental goals, and offers actionable insights for farmers, policymakers, and stakeholders aiming to achieve sustainable nutrient management in the U.S. Midwest.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Li, Ziyi

Contributors dc:contributor

• Guan, Kaiyu
• Yang, Wendy H.
• Nafziger, Emerson D.
• DeLucia, Evan H.
• Peng, Bin

• Nutrient Management
• Crop Yield
• Environmental Sustainability
• Agroecosystem Modeling
• U.S. Midwest

Statement dc:rights

• I am requesting a Closed Access embargo for a period of two years from the date of deposit. During this time, access to my thesis through IDEALS will be restricted, such that it will not be available to anyone. After the two-year embargo period, my thesis will become publicly available in accordance with the University of Illinois Graduate College policy.

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/130208

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F130208