Dvorkin G, Manor M, Sibony M, Chefetz B & Rubin B (2012). Effects of long‐term irrigation with reclaimed wastewater on the efficacy and fate of trifloxysulfuron‐sodium in the soil. Weed Research.52, 441–448. Summary Long‐term irrigation with reclaimed wastewater (RWW) is known to affect the physical, chemical and biological properties of the receiving soil. The sulfonylurea herbicide trifloxysulfuron‐sodium (TFX), an acetolactate synthase inhibitor, is stable in the soil for several months and can carry over to rotational crops; however, its activity in RWW‐irrigated soils is much lower. In this study, we monitored the activity/dissipation of TFX applied on RWW‐irrigated soil. High weed infestation in the treated soil in field studies along with a decrease in the soil activity as determined with test plant was observed, suggesting fast dissipation of the herbicidal activity of TFX in the soil. Dose–response curves of Sorghum bicolor to TFX planted in RWW‐ and in fresh water‐irrigated soils showed higher and more significant damage for both shoots and roots with the fresh water‐irrigated soil. Sterilised RWW‐irrigated soil exhibited higher TFX activity versus non‐sterilised soil. This implies that reduction in TFX activity in RWW‐irrigated soil is probably affected by the microbial activity.