DESIGN AND VALIDATION OF A FRAMEWORK TO ASSESS SUSTAINABILITY IN CEREAL AGROECOSYSTEMS

This thesis develops and applies an integrated framework to assess sustainability in temperate cereal agroecosystems, with particular attention to the interplay between agronomic performance, soil processes, and analytical measurement of crop quality. The work combines field experimentation, quantitative meta-analytical evidence synthesis, and analytical chemistry method development, though the degree to which these components fully converge into a unified assessment approach may depend on interpretation. A three-year field experiment in a continuous wheat system explored the introduction of summer cover crops under contrasting nitrogen fertilization regimes, suggesting that short-term system responses can be uneven, with indications of changes in yield formation, nitrogen use efficiency, and soil organic carbon dynamics that may reflect an early transition phase rather than a stabilized system state. A meta-analysis of temperate rice and wheat systems, based on 425 observations from 66 studies, indicates that cover crops tend to increase grain yield on average by about 9.3%. This average response masks substantial variability across crop systems and cover crop functional type, with more consistent gains in rice and more conditional responses in wheat. These patterns appear to be shaped by interactions between cover crop type and nitrogen availability, though the strength and generality of these interactions remain somewhat context dependent. An analytical chemistry novelty was obtained through the development of a reagent-free approach for multi-element determination in rice using ash-assisted laser-induced breakdown spectroscopy, where improvements in signal intensity and model performance suggest potential for scalable screening, although with some limitations for certain elements and sensitivity to sample preparation. This work points toward the importance of system-specific management strategies and the need to jointly consider productivity, nutrient dynamics, and measurement capacity when evaluating sustainability in cereal systems, while also indicating that variability and methodological constraints may limit the extent to which generalized conclusions can be drawn