Pengaruh campuran herbisida berbahan aktif atrazin 500 g/L dan mesotrion 50 g/L terhadap gulma dominan pada tanaman jagung (Zea mays L.)The effect of herbicide mixture of atrazin 500 g/L and mesutrion 50 g/L to dominant weeds in corn (Zea mays L.) Abstract. Weed control by using a single herbicide continuously will cause weeds resistant, so it is necessary to mix herbicides. Mixture of herbicide with two or more types of active ingredient can be synergistic, additive, or antagonistic. The objective of this research is to know the effect of herbicide mixture of Atrazin 500 g/L and Mesotrion 50 g/L to several types of dominant weeds. The research was conducted from The treatment was consisted of three types of herbicide with six level of doses. There were herbicide Atrazine 500 g/L (1200, 600, 300, 150, 75,0 g /ha), Mesotrion 50 g/L (120, 60, 30, 15, 7.5, 0 g/ha) and herbicide mixtures Atrazine 500 g/L and Mesotrion 50 g/L (1056, 528, 264, 132, 66, 0 g/ha) with four replications. The target weeds were A. conyzoides, S. nodiflora, C. rotundus and E. indica. Data was analyzed by linear regression and MSM method to determine the value of LD50 treatment and LD50 expectation. The results showed that herbicides mixture of Atrazine 500 g/L and Mesotrion 50 g/L had a value of LD50 treatment 85.11 g/ha which is smaller than the value of LD50 expectation (86.9 g/ha), this indicating that the herbicide mixtures was synergistic.