Assessment of engineered sustainable nitrogen fertilizers on lettuce development using physical sampling and image‐based phenotyping

Efficient and sustainable nitrogen (N) management is critical for addressing the dual challenges of maximizing productivity and mitigating environmental impacts in short-cycle crops like lettuce (Lactuca sativa). This study evaluates the agronomic performance and nutrient dynamics of eight N fertilizer treatments, including mechanochemically synthesized urea-based cocrystals, conventional urea, and mechanochemically synthesized carbonate salts alongside accessible digital phenotyping methods for a greenhouse-grown romaine lettuce system. Plant growth, biomass production, chlorophyll content, and soil N residues were measured in conjunction with digital image-derived spectral indices from traditional photography. Engineered sulfate cocrystals (zinc sulfate urea and copper sulfate urea) performed comparable to or better than urea in promoting growth and N use efficiency, while engineered carbonates displayed moderate responses, likely due to slower N release. Traditional image-based indices such as normalized green-red difference index, hue angle, and green color distance metric, as well as more unique visual calculations, effectively captured plant nutritional status and correlated with chlorophyll levels. Principal component and cluster analyses further distinguished treatment performance based on growth and color metrics. These findings demonstrate the potential of combining novel N delivery systems with low-cost phenotyping technologies to transform sustainable nutrient management practices across diverse crop systems.