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Useful links and previous articleswicking_bed_ history.html wicking_worm_beds.pdf Gin Gin school shade house.pdf trailer_katie keeps her cool.wmv |
The Waterright philosophyChapter 5 Wicking bedsOf all the innovations developed to make more effective use of water over the last forty years Wicking beds are the simplest and most effective, successful and are being widely adopted. What makes them so successful;- they grow more food from limited water, soil and space. They look so simple, just an underground pond, so it is easy to overlook the underlying technology. In Water Harvesting I described how desert plant survive, old roots systems create percolation holes which feed water to an underlying clay layer, water moves through the soil to collect at the lowest point to form an underlying pond, and the water wicks up to feed the plants. Why is this so effective? Virtually all the water is used by the plant with no losses from evaporation from the surface and no loss of water past the root zone. The water concentration profiles from totally saturated at the pond to totally dry the surface, there is always a layer with just the right combination of water and air to give maximum growth. In conventional irrigation we water from the surface and have to wait for the water to soak into the ground, the water on the surface is lost by evaporation and if to much water is applied water (and nutrients) are lost to the soil below the root zone. As can be seen from the wicking bed history when I was in Ethiopia I was looking for a way of storing more water. The solution was a simple underground pond formed by a plastics sheet. It is worth explaining how this can hold so much more water that soil by itslef. Normally water is help in the soil by surface tension. If the soil particles are very fine, as in clay, the soil can hold large amounts of water, however the plants have great difficulty in extracting the water so the actual amount of water available to the plant is still limited. (Typically about 10% by volume). By contrast a coarse soil, e.g. sand will only hold a limited amount of water but much of that water will be available to the plants. Using an underground pond the soil is totally saturated (as opposed to being at field capacity). We used scrap organic matter, which is very coarse so a large amount of water an be stored and yet be readily available to the plant as water is used. Using coarse organic matter in the pond means that air, essential for good growth is available for the roots. It also helps fertilize the soil and as it degrades improve its quality and texture. A new horticultural systemIn essence wicking beds are a new horticultural system. Some land is reserved as the growing area using high productivity wicking beds. Other land area, that with less value for agriculture is used as a combination to extract nutrients from the soil, incorporate into plant matter which is then incorporated into the base of the wicking bed.In the same way the less valuable land is used as a catchment for water, just like the desert plants do. A further advantage which we are just beginning to appreciate is that carbon can be captured in the soil. See carbon capture. Wicking beds an be fed from any water source but can also be used to harvest rain by incorporating catchment areas. See DVD Solving the water crisis. to be expandedcarbon capture home |
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 web tracker 27th March 2009 |
