Dissipation of metribuzin, pendimethalin and clodinafop-propargyl, applied in pea, as influenced by mulching and climatic variables

AbstractPea (Pisum sativum L.) is a major legume valued for its high protein content and nitrogen fixation, but persistence of herbicides like pendimethalin, metribuzin and clodinafop-propargyl raises concerns of food safety and their carryover effect on succeeding crops. A field study was conducted to evaluate dissipation kinetics of pre-emergence application (PE) of pendimethalin 750 g/ha and post-emergence application (PoE) of clodinafop-propargyl + metribuzin 169, 202, 236 and 270 g/ha in pea crop with the paddy straw mulch of 7.5 t/ha, under varying climatic conditions that prevailed in different years of evaluation. Clodinafop-propargyl remained below 0.01 µg/g due to rapid hydrolysis into clodinafop acid. The half- lives of pendimethalin and metribuzin varied markedly across years, with faster dissipation in the 2024–25, year with higher early-season rainfall, and slower degradation in the 2022–23 and 2023–24, years with limited rainfall. Mulching increased pendimethalin persistence by moderating soil temperature and moisture, and reducing volatilization and photodegradation whereas clodinafop-propargyl + metribuzin dissipated rapidly when applied over mulch due to greater exposure to sunlight and air. At harvest, residues of all herbicides were below the limit of detection (<0.01 µg/g) in soil and pea across all study years, indicating that at recommended application rates these herbicides dissipate efficiently without leaving harmful residues, thereby ensuring food safety.