Screening best performing herbicides for groundnut ( Arachis hypogaea L.) weed management in arid and semiarid areas in Kenya

Weed management remains a major constraint in groundnut (Arachis hypogaea L.) production in Kenya, leading to substantial yield losses. Currently, groundnut farmers in Kenya have no registered herbicides for weed control, which limits commercialization. Therefore, this study evaluated herbicide efficacy and phytotoxicity effects on the two groundnut varieties in arid and semi-arid lands (ASAL) in Kenya. Field trials were conducted in Siaya and Baringo counties using a randomized complete block design (RCBD) in a split-plot arrangement with three replications. The herbicides tested included three pre-emergent and six post-emergent plus controls: farmers’ practice and weedy check. Data were analyzed by ANOVA using R software, and means were separated using Tukey’s HSD at (p < 0.05). Results revealed significant site and herbicide effect on WCE and phytotoxicity. Clethodim and acetochlor consistently achieved the highest WCE (>75%) and lowest phytotoxicity (0.6–2.4). Post-emergent herbicides (2,4DB, atrazine and metribuzin-post) caused severe phytotoxicity (7–10) on the crop. Strong site and herbicide interaction indicates that uniform recommendations were unsuitable. Clethodim and acetochlor (followed by s-metolachlor) showed the best balance of high efficacy and low crop damage, making them suitable for recommendation to groundnut farmers.