THE FULLSTOP GAME
FullStop Always Activated

The likely reason FullStops are always being activated is because too much water is being applied at one time.

Frequent activation of the deep detector occurs most commonly under drip irrigation, especially on soils with narrow wetting patterns. The irrigation interval should be shortened, and/or FullStops installed deeper in the soil.

Sometimes water does not move through the soil as a uniform wetting front. For example, holes made by decayed roots, earthworms and the like are often continuous, and can therefore carry water to depth without the whole soil profile being wetted.

Some clay soils crack when dry and irrigation water can run down the cracks and reach a FullStop without wetting the soil above. Some sandy soils can develop water repellency and do not wet uniformly; water can move through the soil as 'fingers'. Because the FullStop samples a large area, the presence of worm holes, cracks or fingers can be sufficient to activate the detector much quicker than we would expect. This is because the soil above the FullStop has only been partially wetted.

Normally we expect cracks and holes to be a small problem for drip and sprinkler irrigation. This is because drip and sprinkler irrigation do not totally saturate the soil. In fact the soil remains at a slight suction, which means that cracks and holes should not carry water. Cracks and holes only fill with water when there is a liquid (free) source of water at the surface, such as occurs with flood irrigation.

If the FullStop is quickly activated it is telling us something real - water is moving quickly to depth without wetting the bulk soil. There are several ways we can respond

• pulsing irrigation; the impact of cracks diminishes as the soil wets up
• 'disturb' the soil directly under the dripper so that holes are not connected to the surface.
• placing a handful of sand under the dripper can have the same effect as above
• fill the funnel with fine sand. This must be done before installation. If a crack delivers water directly to the FullStop the fine sand absorbs this water. The dry soil around the FullStop will ‘wick’ water from the fine sand so that the detector will not be activated until the entire zone around the FullStop is fully wet.