Wetting Front Detector (WFD)
When irrigating, water infiltrates into the soil forming a wetting front, this represents the boundary between wet soil above and drier soil below. A wetting front detector (WFD) is able to detect the depth of the wetting front and can be used as a means to manage irrigation. The WFD is a funnel-shaped instrument that gets buried underground and detects when the wetting front has reached a specific depth. The WFD collects the corresponding solution from which one can measure the amount of nutrient runoff. There are a range of articles on WFD on the internet for further reading.