Nitrogen management and harvest timing are critical determinants of fresh bean (Phaseolus vulgaris L.) pod quality; however, their combined effects on morphological, colorimetric and biochemical characteristics during pod development remain insufficiently characterized.
Pod length and width increased with advancing development stages, while pod water content declined from early stages to physiological maturity.
Antioxidant capacity exhibited a stage-dependent pattern, with lower values at intermediate stages and higher values at late development stages, particularly under urea treatment.
Total phenolic, flavonoid and protein content increased significantly at the final development stage.
Overall, the results demonstrate that development stage plays a key role in determining pod quality, while nitrogen source influences the magnitude of these responses.
Nitrogen management and harvest timing are critical determinants of fresh bean (Phaseolus vulgaris L.) pod quality; however, their combined effects on morphological, colorimetric and biochemical characteristics during pod development remain insufficiently characterized. This study evaluated the effects of four nitrogen top-dressing fertilizers (ammonium sulfate [AS], slow-release fertilizer [SRF], nitropower [NP], and urea) and five pod development stages (BBCH 72–81) on pod morphology, color parameters, antioxidant capacity, phenolic compounds, flavonoids, and protein content under field conditions. Nitrogen top-dressing significantly prolonged days to 50% flowering and pod setting times, with the latest flowering observed under urea treatment compared to basal fertilization. Pod length and width increased with advancing development stages, while pod water content declined from early stages to physiological maturity. Colorimetric analysis revealed a marked increase in lightness (L*), yellowness (b*) and chroma values with maturation, accompanied by a decrease in hue angle, indicating reduction in greenness and increase in yellowness. Antioxidant capacity exhibited a stage-dependent pattern, with lower values at intermediate stages and higher values at late development stages, particularly under urea treatment. Total phenolic, flavonoid and protein content increased significantly at the final development stage. Strong positive correlations were detected between antioxidant capacity, phenolic, flavonoid and protein content, whereas pod water content showed significant negative correlations with these quality traits. Overall, the results demonstrate that development stage plays a key role in determining pod quality, while nitrogen source influences the magnitude of these responses. Late harvest stages (BBCH 79–81), together with stable nitrogen sources such as SRF and AS, could be employed to improve nutritional and antioxidant properties of fresh bean pods.
