The Wetting Front Detector (WFD) is a new tool to help measure how deeply water has penetrated into the soil after an irrigation event. The WFD also captures and stores a soil water sample, which can be analysed for its salt or nutrient content. The first commercial version of the Wetting Front Detector (WFD), called the FullStop, was released in 2004. The Full Stop WFD is comprised of a funnel, a filter and a float mechanism. The funnel 'captures' some water from the wetting front as it goes past, and pops up an indicator flag at the soil surface. If the soil is dry before irrigation, the wetting front will not penetrate deeply, because the dry soil absorbs much of the infiltrating water. A long irrigation would be needed to activate a detector. However, if the soil is relatively wet before irrigation, the wetting front moves more deeply into the soil. Experiments with sprinkler irrigation have confirmed this.