Herbicide mixtures are a modern weed management practice as they reduce herbicide application. This study aimes to evaluate the effect of metribuzin, halosulfuron and flumioxazin applied individually and as mixtures (metribuzin:halosulfuron and metribuzin:flumioxazin) on Chenopodium album, Amaranthus retroflexus, and potatoes on biomass and chlorophyll-a fluorescence in 21 experiments. The individual herbicide experimental design was a randomized completely block design with seven doses and three replications. The factorial experiments were performed on the basis of randomized completely block design in three replications for binary mixture experiments. Flumioxazin was very potent in controlling C. album, A. retroflexus, and injured potatoes with a 50% effective dose (ED50) of 1.21, 0.54, and 12.23 g ai·ha−1, respectively. Both mixtures of metribuzin:halosulfuron and metribuzin:flumioxazin generally showed an antagonistic effect on both weeds and potato in 12 independent experiments. Metribuzin, halosulfuron, and flumioxazin significantly decreased photosystem II activity by decreasing the maximum quantum efficiency (Fv/Fm). The metribuzin:halosulfuron mixtures almost followed the Additive Dose Model for Fv/Fm, whilst there was an antagonistic effect for the metribuzin:flumioxazin that was closely related to biomass. The results indicated that mixtures were generally antagonistic, and the endpoint choice is pivotal when assessing the joint action of mixtures.

Frequent use of herbicides might impose a risk for nontarget species, such as earthworms. The objective was to test the combined toxic effect of binary herbicide mixtures: metribuzin:halosulfuron and metribuzin: flumioxazin on a nontarget earthworm in two test systems. Two experiments on filter paper and two on artificial soil determined lethality and chronic toxicity on the earthworm. Results showed the flumioxazin had no high toxicity in contact filter paper test, with the lethal concentration (LC50) of 153.10 µg a.i cm-2 at 48 h. In the artificial soil test, flumioxazin LC10 was 0.65 mg a.i kg-1 on day 14. Metribuzin showed high toxicity to earthworms in the filter paper test with LC50 17.17 µg a.i cm-2 at 48 h but LC10 of metribuzin. Halosulfuron and metribuzin were highly toxic with LC10 value 0.24 and 0.47 mg a.i kg-1 on day 14. The herbicides' mixed effect showed in both test systems antagonistic effect, meaning that the mixtures retracted the herbicides' action in the earthworms relative to a Concentration Addition reference model. A chronic toxicity test showed that earthworm catalase was stimulated by metribuzin:halosulfuron (50:50%) and metribuzin (100%).

Frequent use of herbicides might impose a risk for non-target species. The objective was to test the combined toxic effect of binary herbicide mixtures: metribuzin:halosulfuron and metribuzin:flumioxazin on non-target earthworms in two test systems, a filter paper, and a soil toxicity test system. The joint action experiments were independently run twice to substantiate the findings. The most potent individual herbicide was metribuzin with a 50% lethal concentration (LC50) of 17.17 µg ai. cm− 2 at 48 h in filter paper test. The toxicity of the individual herbicides on filter paper test was ranked as metribuzin > halosulfuron > flumioxazin. In a soil test, metribuzin and halosulfuron had high toxicity with the LC50 8.48 and 10.08 mg ai. kg− 1 on day 14. Thus, the individual herbicide ranking did not change between the filter paper and artificial soil tests. The herbicides' mixed effect showed in both test systems consistent antagonistic effect relative to a Concentration Addition reference model. It means that the mixtures retracted the herbicides' action in the earthworms.