Soil herbicidal activity of clethodim and haloxyfop R-methyl and its phytotoxic effect in maize (Zea mays)

Abstract

The herbicides haloxyfop R-methyl and clethodim may persist active in the soil causing phytotoxic effects to grass crops when applied close to sowing. In this work, field and greenhouse experiments were conducted to evaluate the phytotoxic potential of different rates of these herbicides in maize and to study the irrigation requirements and time between application and sowing to avoid phytotoxicity in the crop. Field experiments were carried out on four agroecological areas. Under field conditions the lower rates of both herbicides, 62.5 and 120 g i.a. ha-1 of haloxyfop R-methyl and clethodim respectively, produced visual phytotoxicity lower than 14 %. At higher rates, in two of the four environments higher levels of phytotoxicity (32-78 %) were registered. Both herbicides reduced maize plants biomass when they were not incorporated to the soil by irrigation and the sowing was carried out 14 days after their application. When irrigation was performed after the application of herbicides, 7 days were enough to avoid phytotoxicity at 62.5 and 125 g i.a. ha-1 of haloxyfop R-methyl and 120 g i.a. ha-1 of clethodim. None of the evaluated treatments reduced the plant biomass of maize planted 14 days after irrigation.