SummaryThe movement and degradation of simazine in the field during winter and summer were measured and compared with simulations using a simple model. The model only simulated simazine behaviour closely when water solubility was taken into account. Relationships between water solubility, melting point, soil adsorption and octan‐1‐ol/water partition coefficient indicate that, at agricultural rates of application, water solubility will only have an important influence on behaviour for relatively polar chemicals with high melting poi