A method for disinfecting agricultural irrigation water system-wide comprises (a) continuously feeding chlorine to the irrigation system and (b) monitoring an outer field point to determine whether at least a detectable level of residual chlorine is seen at that point, whereby chlorination disinfection system-wide is achieved. An enhanced irrigation system which is adapted for disinfecting agricultural irrigation water system-wide includes (a) apparatus for continuously feeding chlorine to the irrigation system and (b) apparatus for monitoring residual chlorine at an outer field point (to determine whether at least a detectable level of residual chlorine is seen at that point) for the purpose of achieving chlorination disinfection system-wide.