“Testing of only one variable at the same time,” has sometimes been described as one of the criteria that a scientific field trial has to satisfy. In projects involving cooperation between farmers and scientists, scientists have sometimes been “frustrated” with farmers whose experiments have not satisfied the one-variable requirement. Reportedly, this is “one of the points that has [led] research station scientists to dismiss farmer innovation.” This study investigates methodological and philosophical issues pertaining to farmers’ experiments such as the choice of interventions to be tested, the planning of experiments, and the means to deal with confounding factors. [Hansson, S. O. Farmers’ experiments and scientific methodology. European Journal for Philosophy of Science 9, doi:10.1007/s13194-019-0255-7 (2019).]