BioDesign N/L 11.07.11- Drought and the Porous Pot - LED 12v Lighting July 13, 2011
Date: 11 July 2011 07:36
Subject: BioDesign N/L 11.07.11
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For many thousands of years people have been making pots from baked clay. No doubt it was an accident when they discovered that some sand in the mix meant that the pot leaked but that slowly ouzing water cooled the interior of dwellings during hot summers.
However now, even in the most distant parts, modern life has caught up with people and provided them with cheap plastic buckets. So the practice of baking clay pots is slowly dying out and they are often now quite expensive. For irrigation during droughts alternatives need to be found !
Recently a professor, David A. Bainbridge, who had been researching drought conditions in US deserts came up with several techniques, including wicks, to keep tree saplings alive – just alive - during drought periods. Visit - http://www.amazon.com/Guide-Desert-Dryland-Restoration-Ecological/dp/1559639695 In this book he recommends wick irrigation as a promising technique in the future!
One other possibilty is to have a 'vessel' above ground with wicks supplying water to plants/saplings surrounding the 'pot'. It could be a plastic bucket or trough.
Where polythene sheeting is available this could be formed into a very cheap covered trough with earth/stone each side. If the ground is flat the trough could be quite long with wicks projecting from both sides.
A possible substitute for porous pots might be achieved by using canvas to line holes sunk in the ground. If you have access to canvas and want to try this, do get in contact!
Where cheap hosepipe is available there are many other possibilities including automatic filling!
More later. Ask for our wick summary pdf if not yet seen.
Hello Graham. It's the rainy season at our farm in northern Nicaragua but last years dry season drought was terrible for all of the farmers in the area. We experimented with the clay pots, had 250 of them made by a local man and planted them alongside small fruit trees. They worked very well but we saw that going from pot to pot to fill up every several days was time consuming. The great majority of the trees survived the drought though, as a testament to the effectiveness of the system. I would like to help out with the wick experiment, particularly if it comes from a central water container! Just let me know what to do.
Thanks. Jeff Higgins
My friend, Richard Garstang, who recently retired as head of the Pakistan Wetlands Programme (which he helped to establish), would always rave to me about “pitcher irrigation”. This is a traditional and rather ingenious way of growing plants in very dry areas by burying a porous clay pot full of water into the ground next to the seedlings.
The very old and cheap technology (apparently the Chinese used it thousands of years ago) is ideal for an arid country like Pakistan and could easily be used on a large scale if more people knew about it. Just about any farmer or gardener can use these unglazed clay pots (made everywhere in Pakistan’s rural areas) to grow vegetables and a wide variety of other plants.
I finally got a chance to see pitcher irrigation up close during my trip to the Makran Coast recently. In Gwadar, the town’s administration was advised by the Pakistan Wetlands Programme to use this technology to keep the sand dunes at bay, which are threatening to cover the roads that have been built for future housing projects. There is very little rainfall in Gwadar (around 22mm per year) and freshwater is scarce and expensive (brought in by tankers from a dam 20km away), hence the Gwadar Development Authority took to the idea and decided to experiment on a road near the beach.
They decided to plant mesquite to control the sand dunes using a pitcher irrigation system. Mesquite plants grow quite fast, and form shrubs within 10-12 months if they survive. They also don’t require that much water and are hardy plants that can stabilise sand dunes. I was informed that the pitchers, buried in a row next to the road at intervals with covered lids, only need to be replenished every 15 days.
Pitcher irrigation makes very efficient use of water since it delivers moisture directly to the plant’s roots. Water poured into these pot seeps slowly into the soil,
feeding the seedling or plant’s roots with a steady supply of moisture. Pitcher irrigation has been used to grow a wide range of plants in China, Pakistan, India, Iran, Mexico, and Brazil.
Apparently, the rate of seepage of water from the pitcher depends on the type of plant and the soil and climatic conditions around the pot. When the surrounding area becomes saturated with water and the pot is emptied, water will tend to move back to fill the pot. The system is therefore self-regulating. One just has to ensure that the pot is never completely empty of water.
Pitcher irrigation has also been used successfully in other wetland projects on the Makran Coast. In the Dasht area, which is a desert, the villagers are growing creeper vegetables like cucumbers, pumpkins and bitter gourd and this has hugely improved their nutritional intake.
Experts say that the water requirements in a pitcher irrigated field can be even less than those of a drip irrigated system due to the very low permeability of the pitchers, as well as reduced evaporation losses. Of course, growing crops in large areas requires buying quite a few pitchers! However, pitcher irrigation is still ideal for small farmers living in remote areas where vegetables are expensive and hard to come by. The cost of pitcher irrigation is also much less than that of drip or sprinkler irrigation methods.
On the whole, pitcher irrigation is great for growing vegetables, for gardening and landscaping, and for growing plants in containers on patios or porches, where the clay pot is buried in the planter box. Limiting water delivery to the area where the plant is grown also dramatically reduces weed growth. The pots can be refilled every few days instead of requiring constant attention.
Back in Gwadar, I could see clearly how the mesquite shrubs are holding back the sand dunes and preventing them from spreading onto the expensive asphalt roads (which criss-cross the entire coastal section of Gwadar). In fact, we drove further along the road to the outskirts of town where the project ended and up ahead we saw how the road had completely disappeared under tonnes of sand.
If it were not for the mesquite grown by the pitchers, large sections of this road would have been submerged by sand long ago. My friend Richard Garstang was right; pitcher irrigation is an ingenious solution to our water woes and really should be practiced everywhere in Pakistan — in home gardens, in small farms, and in public parks and green belts where so much water is wasted.