Where Does The Water Go?
Growing For Market, September 2004

Almost every one on earth who lives where rainfall is sporadic applies water to plants be it to a few flowers in a small garden bed, a lawn, trees in an orchard or to a 250 acre field of broccoli, yet very few of us have any understanding of how the water is traveling down through the soil or how efficiently it is being used by the plants. We also have no idea of just when the water we have applied has gone below the root zone of the plants only to be wasted or to result in down stream pollution.

The FullStop wetting front detector is a totally new tool that will give answers to all of us who water plants.

Too little water If the indicator of the shallow detector rarely pops up, then water is not moving deep enough to fill most of the root zone. More water should be applied.	About right The indicator of the shallow detector to pop up regularly after irrigation. The deeper detector should respond during periods of high demand for water.	Too much water If the indicators of both the shallow and deep detectors regularly pop up then water could be wasted. Apply less water or lengthen the period between irrigations.

There are very few inventions that are simple, elegant, work well and are cheap to produce. FullStop is all of these, Dr Richard Stirzaker, a scientist with Australia's Commonwealth Scientific and Industrial Research Organisation has come up with a brilliant invention which won the International Commission on Irrigation and Drainage's WatSav technology award in 2003.

The plethora of available instruments (tensiometers, TDR, gypsum blocks, suction cups etc ...) used to measure water content of soil provide the user with numerical data of various degrees of accuracy. Numbers, which the majority of smaller scale growers have difficulty interpreting and then using, when making irrigation decisions.

FullStop differs from all these instruments in that it gives a simple yes or no signal indicating whether or not a wetting front has moved through the soil. It does not tell us how wet or dry the soil is, it gives the answer to the question "how deep has the water gone?"

The strengths of a FullStop are that it is simple, inexpensive and easy to use. Anyone who has used a computer to solve complex problems has benefited from what can be done by a simple on/off signal. Likewise the value of the on/off message that FullStop provides must not be under estimated. Anyone intrigued by this device, which signals the passing of a wetting front, will soon be asking the question "how long will it take for the FullStop to pop up?". Instead of reading a number off a dial for future use the user will be starting to learn how wet the soil is and how thirsty the plants are. Indeed FullStop will start to teach gardeners and large and small scale irrigators about what happens when you water a plant or irrigate a crop.

The other remarkable feature of this clever invention is that it enables easy sampling of water that has passed down through the soil. Water that can be tested for nutrients and other, less desirable, salts.

Relevance

We run a small scale, fully integrated, organic market garden 30 miles north of Canberra, Australia's capital. We have limited water collection in our dams (ponds) and a bore hole that provides us with slightly saline water. The last four years have proved to be very dry and water is an increasing issue.

We have been using prototype versions of the FullStop wetting front detectors for three years and continue to be amazed by how this simple device has changed our attitude to how we use water.

Until Dr Stirzakar gave us some prototype FullStops we had no method of either measuring soil moisture or scheduling irrigation. The size of our operation did not justify expensive monitoring equipment despite our concern about water use. We are experienced vegetable growers and were quite taken aback by how wrong we had been when we watered. FullStops quickly pointed out that when we were using drippers we overwatered early in the season then proceeded to under water when the plants moved into their rapid growth stage.

On the other hand we are still amazed at how long it takes for sprinklers to put on enough water to really soak the soil when it is dry and yet how quickly a small shower of rain will penetrate if the ground is already damp.

FullStop has also enabled us to use our bore water safely and productively. We now have the ability to collect and measure the salt content of the water getting down into the root zone of our plants. This allows us to make informed decisions about when the soil needs to be given a flushing irrigation and how long that irrigation needs to be.

Any tool such as a FullStop, that has the potential to change peoples attitude towards water use will have a significant impact on Australia's or indeed the world's environment.

Communication

Over the past three years we have not only had the opportunity to experiment with FullStops in our own vegetable operation but we have watched prototype FullStops being introduced to Australians at the Australian Broadcasting Corporation's open gardens, small farm field days and national irrigation conferences. It does not matter whether the audience is 9 year olds intuitively explaining a FullStop to a parent, crusty old backyard vegetable growers, young and enthusiastic environmentalists, commercial growers or Department of Agriculture extension officers, they are all engaged by this simple piece of technology.

FullStop is a tool that has the ability to break down the barriers between scientists and water users.

As yet FullStop has not been available to the public other than in limited numbers of prototype models so it is difficult to know what the final ramifications of this innovation will be, however, we would anticipate that the commercial model, which is now available, will become common place in gardens, farms and schools over the next few years. FullStop has the potential to challenge everyone's preconceived notions about what happens to water when we water or irrigate.

Richard Stirzaker, a scientist and keen vegetable and fruit grower, has come up with something truly remarkable in irrigation technology and deserves the thanks of everyone who waters a plant on whatever scale and is concerned with conserving this most precious resource.