by Otto Muller
In areas where the normal rainfall is only marginal and very often insufficient it is often possible to greatly increase success rate when planting tree or bushes by using techniques of water concentration. Water concentration means creating conditions where part of the rainfall in an area is encouraged to run off from an area where it is not essential into an area that essentially require all the moisture we can get there.
In afforestation projects in India, the Indian Forest Service practiced water concentration by digging pits where water from adjoining areas would accumulate. In undisturbed areas the rainwater penetrated 15cm, while in the pits it penetrated 1 meter assuring the establishment of the trees planted. In its most simple form on a level field, it would simply mean making a very shallow furrow of say 2m wide and some 15cm deep. The center of this furrow would be cultivated and the tree or bush would be planted there.
When there is a rain of say 10mm, the amount of rain in a meter length of this furrow would be 20 litres of water. If only half of the rain runs into the centre it would mean that the tree or bush would get some 10 litres of water over a 1 meter length.
If we have a similar set of circumstances on a slight slope we simply would establish a furrow 2 meters wide with its lowest point at the bottom.
If we now intend to plant a tree or bush at say every 2 meters and want to concentrate every possible amount of moisture into this area we could make a shallow pit with the centre of about 15—20cm. We now have an area of 4m2 draining into an area of 0.04m2. If we now again have 10mm of rain and half of it runs into the centre, we now have 20 litres of water draining into an area of 0.04m2 which would be equivalent to receiving half a meter of rain.
The concept of water concentration would be a tool that would greatly enhance the percentage of survival in establishing trees or bushes where conditions are suitable. For example in the Sinai Desert scientists have been able to grow 1 hectare of wheat on an area of 40 hectares from run-off from the desert. This is without any water storage. Under normal circumstances every particle of soil is surrounded by a film of water. This makes it possible for rain to penetrate into the soil. However if the soil is really dried out in the middle of a severe drought, this film of water also dries out and when rain finally comes; it is not able to penetrate into the ground and runs off like water on a greasy pan. This increases the run-off to almost the total rainfall, which means in the above example the rainwater running into the centre would be almost equal to 1 metre of rain.
At one time I was involved in a feasibility study into a desert afforestation scheme and at that time I made myself familiar with the technology available to carry out this operation on a large scale, The implement used is called a Basin Lister and it consists of a tractor drawn tool something like a snowplough. but with its nose pointing down. The implement is supported on an axle, which has a crank in the middle and the implement now lifts and lowers with every revolution. This produces a lifting and lowering based on a sinus curve. The alternative is to use a cam and roller. With this system it is practical to make almost any pattern of lifting and lowering of the implement. The most effective pattern is to create a diamond shaped depression with a regular slope. It would be quite simple to combine this set-up with a tree planter, which plants the trees or bushes into the centre of the depression. The wings of the implement will cut the turf and deposit it on the side, which allows the young tree or bush to get a start without the usual competition from surrounding vegetation. The technique of water concentration is only practical where the soil is of considerable depth and where it has a tendency to allow water to run off.
I visualise that water concentration would be an important factor in establishing a paddock of browsing bushes in an area with generally low rainfall. It would also increase growth rate and rate of survival when planting plantations or shelter belts under conditions where moisture stress is a very serious problem. In the enclosed illustration about the afforestation on the Jumna River bank only poor quality scrub could grow. With the help of water concentration, it was possible to plant Babul trees (nitrogen-fixing producing a profusion of beans edible for livestock), which 4 years after planting had reached 6 meters height and growing vigorously.
Water concentration requires certain conditions to be successful, above all a soil that is deep enough and a soil structure and a rainfall pattern, where run-off will take place. Incidentally the Jumna River used to be my favourite fishing ground, when I was working in Northern India. The eroded river banks looked something like the Badlands of Dakota, but could be transformed into a highly productive forest that also provided feed for large herds of livestock who fed from the large quantity of edible beans that fell off the trees.
The note regarding water concentration is also based on work I did in India as well as experience on our farm where we established a large number of trees on a rainfall of some 30 cm per season. In India I was involved in a feasibility study regarding a desert afforestation scheme and made myself familiar with the techniques used for large-scale implementation of such a project. The project was to study the feasibility to establish a shelterbelt across the fringes of the Thar Desert. The proposed shelterbelt was going to be 450 miles long and 5 miles wide. While the study proved that such a project was feasible and the actual work was practical, the Indian government decided to irrigate the area with the giant Rajasthan Canal Project which irrigated 10 Million acres of desert which made the proposed shelterbelt unnecessary. It was a great experience personally.
I enclose also some rough sketches to illustrate the notes. Also a copy of the newspaper article about the Webster project in Tasmania. It is interesting that they are budgeting to harvest 4000 tons of walnuts a season, which in our country and on the world market would be worth some $18 million or $36,000 per hectare.