KGML-N: a knowledge guided machine learning modeling framework for efficient simulation of N-yield response

Applying the optimal amount of nitrogen (N) fertilizer is a critical challenge in corn farming, balancing crop yield against fertilizer costs and environmental risks. While scientific tools exist to guide these decisions, they face a trade-off. Complex process-based (PB) models are detailed but inefficient for large-scale use, while simpler data-driven models are fast but often unreliable under new climate conditions. This thesis confronts this challenge by developing and validating a surrogate model KGML-N—a highly efficient machine learning model trained to emulate the functions of a comprehensive PB model (ecosys). We designed a Knowledge-Guided Machine Learning (KGML) model, named KGML-N, whose architecture is inspired by the known scientific principles of crop growth and N cycling. This approach aims to retain the scientific integrity of the original model while dramatically increasing its computational speed. Our research question focuses on whether KGML-N can maintain high fidelity to ecosys and achieve consistency with existing knowledge about environmental impacts on N-yield response. To achieve this objective, we generated a large synthetic dataset over the 3I (Illinois, Iowa, Indiana) states by running ecosys across thousands of scenarios covering 21 years of weather regimes from 2000 to 2020 and various soil types sampled for each county. The KGML-N model was trained on this data to predict yield and a dozen key environmental variables. The model was then calibrated using real-world experimental data and tested through a series of virtual experiments involving changes in temperature, precipitation, and soil organic carbon. The results demonstrate the high performance of KGML-N. Our KGML-N model achieved high fidelity, accurately reproducing the predictions of the original ecosys model and correctly capturing complex interactions between crop characteristics, management, and the environment. Furthermore, its responses to climate and soil changes were consistent with decades of established agronomic knowledge. This work validates the KGML surrogate as a powerful, fast, and scientifically sound tool, providing a new pathway for developing more accurate and scalable N management recommendations for a sustainable agricultural future.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Liu, Qi

Contributors dc:contributor

• Guan, Kaiyu
• Lee, DoKyoung
• Peng, Bin

• machine learning
• nitrogen fertilizer-yield response

Statement dc:rights

• (Copyright 2025 Qi Liu)

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132712

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132712