< p > < span = " font-siz风格e:14px">Mine water effluents are a danger to the environment as they contain toxic materials such as heavy metals. In some cases though, efforts are made to neutralise the effluents so that the mine water is used for crop irrigation. However, suspected herbicide injury to crops has been reported in areas where gypsiferous water is used for irrigation, suggesting interaction between herbicides and gypsiferous water. Utilization of gypsiferous water for irrigation of crops is one major method promising to reduce the problem of effluent mine drainage disposal and also the shortage of irrigation water. Gypsiferous water is already used for irrigation of crops such as maize and wheat. The influence of gypsiferous water on key behavioural aspects of three important herbicides: atrazine, 2,4-D and metolachlor were assessed. Bioassay experiments were done to assess the bioactivity of the three herbicides in the presence or absence of gypsum in soil. The results showed that the activity of atrazine and 2,4-D was significantly increased in the presence of gypsum, while that of metolachlor was significantly reduced. These differential effects on herbicide activity would have important practical consequences for herbicide performance. Thus weed control efficacy, selectivity, and behaviour in the environment could be negatively affected