Prior to July 2010 we had been over-using water at Strawberry Fields. This disturbed me for a number of reasons. One was that it was a poor example to the local community who do not have a limitless water supply to spray all over the place. The second was the huge water bills we were receiving. The third was the un-sustainability of using huge amounts of ground-water in a semi-arid area. As project director I had not been in charge of operations on the ground, and I was not able to attack this issue myself, other than by trying to encourage the focusing of the zone 1 irrigated beds into as small an area as possible, with limited success. In July I took over the running of the Permaculture project on the ground and the first thing I did was to begin installing the drip system I had been dreaming of for almost 2 years.
The benefits of drip irrigation are fantastic and any dry-land agriculture should make use of it (unless it is on the banks of the Nile) as the water use efficiency is about 3 to 4 times as great. Drip is not difficult to construct either and it is a complete lie that lots of fancy high tech equipment or special skills are required. Our system comprises a 1000l tank raised 2m off the ground on a wooden tower. Water fills the tank from 2 sources: one from the guttering of our restaurant/kitchen/store block which happens occasionally; two from the mains water supply which is on twice a day 5am–7am and 5pm–7pm but is also not totally reliable. 2m of fall is enough to supply the whole system effectively as the pipes do run slightly down-hill across much of the system. A 1” main pipe leads out from the tank and runs down the centre of the upper part of the garden and along the southern edge of the lower part of the garden. 4 side branches lead off the main pipe, 2 in the upper garden, 2 in the lower. These are rubber tubing of 10mm external diameter. These tubes are secured in position by holders made from 5mm re-bar bent into a curl at the top which holds the pipe. It is important to keep the tubes off the ground as the drip holes can be blocked up with mud if the tube sags on the ground. Normal mineral water bottles are cut into open ended sections which sit on top of the soil like cups without a bottom. A notch is put into the upper rim of the cup at each side and the tube sits in the two notches. Each drip point will be over one of these cups, which achieves several things: the first is holding the drip point off the soil even if the hose goes slack, the second thing is that as the water drips onto the soil it will obviously make it wet and therefore soft. As a result the weight of the hose will push the lower rim of the cup slightly into the soil. This means that, if the drip point is dripping too much water the cup will actually hold the water there and prevent it from running off over the soil, which is what erodes the soil.
As for the drip points themselves they are simply small holes made with a Stanley-knife and kept open with an acacia thorn. The holes do occasionally clog up with algae or some other form of biological gunk meaning that the thorns have to be adjusted once or twice a day. Someone has to go round and check each drip point. That and keeping the tank topped up are the two main tasks in operating the system. One person can do it easily.
We now use about 2m3 of water per day with this drip system, whereas we used to use 4–6m3 per day with the hose. The labour of operation is minimal, there is no splash erosion of the soil and no damage to the plants as you get when dragging a hose around the beds. However the greatest thing about the system is its productivity.
When you hose a bed the water soaks the top two or three inches of the soil across the whole surface of the bed. It does not penetrate much further than this in the 30 seconds the water is gushing onto the bed. As a result, when the heat of the day reaches its peak, the top 5cm of the soil quickly dries out and the bed is dry pretty soon. What’s more, the plants searching out the water, have put out all their roots into that top 5cm of the soil and are consequently beginning to wilt by 12pm, on a daily basis. They won’t do very well like this and when there is a break in the water supply they won’t last long at all. The situation with the drip is quite different. Here the water is focussed onto a point in the bed and released slowly and continuously. It seeps into the soil and spreads out in all directions, both vertically and laterally. As a result it gets deep into the soil making it moist to a radius of about 30cm in all directions. If at midday the top 5cm of this area dries out, it won’t matter as the 25cm below this will still be moist and the plants will have put their roots deep down into the moisture. Consequently the plants remain vibrant and shiny even at 30°C. What’s more, as the plants grow up over the drip point they shade it, further reducing the evaporation, and turning the drip point into a miniature cool microcosm – a bit like a tiny spring. With 100 or so such cool green microcosms dotted along the 50m length of the drip line it is easy to see why the tomatoes, carrots, beetroot and ginger are looking so happy. But the most surprising thing is that the trees around the beds are also loving it. We could not believe the results, with mangoes putting on fresh growth in the middle of the dry season, which we had not seen before. Even the taller species like Terminalia and Moringa are responding. Lastly, our resident funny Scotsman noticed that as the drip irrigation was increasing the amount of greenery, it was attracting a large amount of new birds to the more lush areas as well.
Making this system of relevance to the community in Konso is not a difficult task either. We have scaled it down, to cover an area of about 20m2 with one line 20m long fed by a single barrel into which dirty washing water can be poured though a sand filter. Our scaled down model even accepts hand wash water from our restaurant guests!