Weed control in maize (Zea mays L.) with effective minimum rates of foramsulfuron

Dose-response experiments were conducted under controlled conditions to determine the effective minimum rates (ED90) of foramsulfuron for 11 weed species that occur in maize growing areas in Turkey. Annual weeds were collected from maize fields in the cotyledon stage and transferred to pots containing a mixture of soil-turf (1:1 ratio). Perennial weeds were grown from rhizome pieces collected from infested fields. Weeds were then treated with different rates of foramsulfuron to determine the effective minimum rate (ED90) for each weed species via dose-response experiments. Results showed that ED90 rates were lower than the recommended herbicide rate for most weed species. Weeds were grouped with respect to their sensitivities into 5 different groups: ED90 25%, ED90 between 25% and 50%, ED90 between 50% and 75%, ED90 between 75% and 100%, and ED90 100% of the recommended herbicide rate. In additional field experiments the performance of these rates applied alone or in combination with ammonium-sulphate on weed and maize grain yield was evaluated, and ED90 rates were determined for some weed species. The results show that 25% of the herbicide rate alone insufficiently controlled weeds; however, the addition of AS improved the effect of this rate. In general, the 50% rate was as efficient as the recommended rate and provided similar maize yield as obtained from plots treated with higher rates or from weed-free control plots. As compared to the ED90 rates determined under controlled conditions, effective minimum rates observed under field conditions were similar for some weed species, but higher for some others. In the case of total weeds the ED90 rate of the herbicide corresponded to 54% of the recommended herbicide rate. Results of these experiments suggest that weed control in maize can be effectively achieved with about half the recommended rate of foramsulfuron, without a loss in yield.