Phytotoxicity of pyroxasulfone and pendimethalin, individually and in combination, in non-target vegetable crops

Herbicides are increasingly used in modern agriculture, yet their unintended effects on adjacent non-target vegetable crops remain insufficiently investigated. This study evaluated the individual and combined phytotoxic effects of two pre-emergence herbicides, pyroxasulfone and pendimethalin, on nine non-target vegetable crops during early seedling development, integrating dose–response modeling (GR50), toxicity index (TI) assessment and onion root-tip cytological analysis. All treatments produced significant dose-dependent suppression of seedling growth, with dry weight emerging as the most sensitive indicator of herbicidal stress. Pendimethalin caused stronger growth inhibition (7.87 ± 1.41 to 60.76 ± 1.54%) than pyroxasulfone (3.27 ± 1.81 to 52.17 ± 0.68%), while combined exposure produced the greatest reductions across crops (11.02 ± 0.79 to 71.55 ± 1.22%). Highest Single Agent (HSA) analysis showed that fixed-ratio mixture produced greater growth inhibition than the individual herbicides, whereas Bliss independence indicated crop- and dose-dependent interaction outcomes. Onion was the most sensitive crop based on GR50, while metha and pea were comparatively more tolerant. Cytological analysis revealed reduced mitotic index and increased chromosomal abnormalities, particularly under combined treatment. These findings demonstrate that herbicide mixtures may produce greater phytotoxic responses than individual compounds, highlighting the importance of species-specific ecological risk assessment and herbicide stewardship.