Compost Making at Chipoli, Southern Rhodesia
COMPOST of a kind has been made at Chipoli for a number of years, but till Sir Albert Howard's methods were mastered some years ago the waste of material had been considerable, the product unsatisfactory, and the cost, in comparison with that now produced, high.
Deep pits were used and the process was chiefly carried out under anaerobic conditions, with the result that it took many months and most of the nitrogen was lost. Farm-yard manure was stored either in the stockyards or in large solid heaps, with the result that when the mass was broken up to be carted on to the fields most of the nitrogen had been lost, and much of the coarse grass, reeds, and similar matter used for bedding remained fairly well preserved, much as bog oak in the mud, and the process of decomposition remained to be completed in the soil with the growing crop, much to the detriment of the latter.
At Chipoli the compost-field has been laid out on the same principle as at Indore. Water is laid on and standpipes are situated at regular intervals. One-inch rubber hose-pipes are used to spray the water on to the compost heaps. With this arrangement compost can be made at any time of the year, the normal process taking almost exactly three months.
It has been claimed that it is cheaper to make compost in heaps alongside the lands where the raw material is grown and to rely on the rains for the water. If the rains are regular this acts quite well; but this is not always the case, and with the interruption of the process the finished product is not so good. Another objection to making compost away from an artificial water-supply is that the material to be composted cannot be used the same season, with the result that a year is lost. I have known seasons when the sequence of the rainfall has been unsuitable for the completion of the manufacture, with the result that the position of a farmer who had been relying on this method for the provision of compost to maintain the fertility of his lands would be serious. The cost of a water-supply is a small insurance premium to pay for certainty of manufacture.
I find pits unnecessary even in the hot weather. If the heaps are sprayed over every day it is quite enough to maintain the correct degree of moisture, and one native can easily control 500 tons. To apply water in buckets is not satisfactory: the material does not get a uniform wetting -- too much is thrown on one place and too little on another.
As the heaps are being turned, a controlled spray keeps the moisture content correct.
The question of cost is raised against the central manufactory. I am of opinion that the small extra cost of transportation is far more than offset by better supervision and the control of the process. The cost of moving the raw material can be reduced by stacking the san hemp, or whatever is being used, in heaps, and allowing it to rot to a certain extent. This considerably reduces the bulk.
The material used for making compost at Chipoli is mostly coarse velt grass which is cut from river banks, dongas, and wherever it is available; next in bulk is san hemp grown for the purpose, and then rushes, crop wastes, weeds, garden refuse, and so forth.
Compost is returned to the san hemp stubble and the land then ploughed. In the past large quantities of san hemp have been ploughed into the land to maintain the humus supply. In some seasons this works quite well, but in others, owing to unfavourable weather conditions, quantities of unrotted vegetable matter are left on or under the surface, to be decomposed the following season before a crop can be planted. By cutting and composting this surface growth and returning it to the land, everything is ready for planting as soon as the rains commence. Again, compost made from combined animal and vegetable waste has evidently some great advantage over humus derived from the top growth of a green crop only.
In making the heaps, a layer of vegetable waste is put down; the heaps are built about 25 yards long and 15 feet wide. Dung and urine-saturated bedding is then laid on top and on this is spread the correct quantity of soil and wood-ash; the whole is then wetted from the hose-pipe and the process repeated till the heap is some 3 feet high. Heating commences at once, and after some ten days, when fungous growth has become general, the heap is turned and more water applied if required. Two heaps are made side by side and if the bulk has become reduced considerably, as generally happens by the time the third turning is due, the two heaps are thrown into one. This maintains the bulk and so ensures that the process goes on properly without any interruption. Should action appear slow at the first turning, compost from another heap -- which is being turned for the second time and in which action has been normal -- is scattered among the material as it is being turned; inoculation thus takes place and the process starts up as it should.
I have found that a mixture of grass and san hemp acts much better than either san hemp or grass alone.
It has been the practice to lay coarse material on the roads and to allow wagon traffic to pass over it for some time; this breaks it down and action is much more satisfactory when manufacture commences. A better plan is to pass all the raw material through the stock-yards, where it becomes impregnated with urine and dung and gets broken up at the same time by being trampled. All that is then necessary in making the heaps is to mix this material with soil and wood-ash and moisten it.
It has always been the routine to broadcast some form of phosphatic fertilizer on the lands. This is now added direct to the compost heaps and so reaches the fields when the compost is being spread. The cheapest form of manure to be bought locally is bone-meal; besides phosphate this contains about 4 per cent. of nitrogen. Dried grass, the chief source of raw material, contains about one-half per cent. of nitrogen; this is very low, so that the addition of the extra nitrogen in the bone-meal assists the manufacture, and none of the nitrogen is lost. This addition of bone-meal is simply a local variation and is in no way necessary for the working of the process.
This year a spell of very wet weather converted the open cattle-yards into a quagmire. As soon as possible the sodden bedding and manure was carted on to the compost field and built into heaps with a liberal interbedding of soil. The material was so sodden that it packed tightly and a dark-coloured liquid exuded from the heaps. The material was turned immediately and more soil added, which absorbed the free liquid. After an interval of three days, a further turning took place and with this the swarms of flies, which had followed the manure from the yards, disappeared. Heating was slow, so a further turn was given; at each turn the heaps became more porous; with this last turn, heating became rapid and the fungous growth started, normal compost manufacture having commenced. Now that the principle of turning with the consequent aeration is understood, losses which took place in the past through improper storage will be avoided. One is reminded of the family midden in countries like Belgium, with their offensive smells and clouds of flies; if the composting principle was understood, what loss could be avoided and how much more sanitary would conditions become!
The chief inquiry with many people before commencing compost making is that of cost. This largely depends on local conditions. Labour costs and the ease with which the raw materials can be collected are the chief factors. I happen to grow tobacco and to use wood as fuel for curing; my tobacco barns are close to the compost field so that my supply of wood-ash is both plentiful and handy. The stock-yards are situated close at hand, through which in future it is hoped to pass all the vegetable wastes. It has been found that san hemp hay makes an excellent stock food; stacks of this will be made alongside the compost field and feeding pens put up where the working oxen can get a daily ration, the refuse being put on to the heaps.
Compost making has been going on for too short a time here to be able to give definite costs. A particular operation that costs a certain sum this year may have its cost halved next year as methods of working are improved. As an approximate indication, however, the following will serve.
On a basis of turning out 1,000 tons of finished compost, collecting all the raw material and spreading the compost on the field.
For those who do not know, a South African wagon is generally 18 feet long; it is drawn by a span of sixteen oxen and holds a normal load of 5 tons. For carting vegetable wastes I make a framework of gum poles which sits on the top of the wagon and so greatly increases its carrying power for bulky materials. Sometimes two or three such wagons work on compost making the same day, and sometimes not any, but an average would be one wagon full time for four months. Such a wagon requires a driver and a leader and two other men for loading and unloading with the help of the driver and sometimes the leader. Labour for cutting and collecting the coarse grass, reeds, &c., works out at about ten natives every day for two months. The san hemp is cut with a mowing-machine and collected with a sweep, say four natives for one month. As regards the manufacture itself, four natives for five months can attend to everything. This gives a total of 1,800 native days. For spreading the finished compost some people use a manure-spreader, which does an excellent job, but such an implement would be too slow for us.
PLATE XIII: Compost Making at Chipoli, Southern Rhodesia
General view of composting area.
Watering the heaps.
On Chipoli three wagons are used for spreading at the same time; each wagon carries something over 3 tons of finished compost. Four natives fill the wagons at the heaps and as soon as a wagon arrives in the field it is boarded by four other natives with shovels or forks who spread the compost on a strip of predetermined width as the wagon moves slowly along. On an average, taking adjacent and more remote lands, one wagon makes eight trips a day; thus with a total of fourteen natives we spread some 75 tons of compost a day. Spreading 1,000 tons thus takes 200 native days. In other words, the whole operation from cutting the waste materials to spreading the finished product on the land takes 2,000 native days. This means that the work of two natives for one day is required for each ton of compost made and spread on the land.
To the above must, of course, be added the upkeep and depreciation on wagons, mowing-machine, &c., when engaged on this work, but this is quite a small item. The ox is not taken into account, as not only does he assist in the manufacture by providing waste material, but when his term of service has come to an end he is fattened up and sold to the butcher, generally for a sum at least as much as he cost.
My water service, made from material purchased from an old mine, was written off after the first season.
I made the statement recently before the Natural Resources Commission that, if compost making became general in Southern Rhodesia, the agricultural output of the country could be doubled without any more new land being brought under cultivation.
Last year the bill for artificials on Chipoli was roughly half of what it used to be, and if the state of the growing crops is any indication the out-turn will increase by fifty per cent.
This season compost has been used on citrus, maize, tobacco, monkey nuts, and potatoes. A neighbour was persuaded, somewhat against his will, to make some compost; this he did and applied it to land on which he planted tobacco: he now tells me that that particular tobacco was much the best on his farm.
Some photographs published in the Rhodesia Agricultural Journal show in a striking manner the drought-resisting properties imparted to land after being dressed with compost. The maize plants on the land to which compost had been added show almost no signs of distress, while those alongside on land that had no compost are all shrivelled up. Properly made compost has the property of fixing a certain amount of atmospheric nitrogen. To do this to the best advantage it appears necessary that the manufacture should be carried out as quickly as possible. There must be no interruption, and the material must on no account be allowed to dry out or to become too wet. I am inclined to use more soil than is absolutely necessary; it costs nothing, and the small extra charge in transport is more than covered by its presence as a form of insurance against any nitrogen that might be given off' which it tends to grasp and fix. We at the present stage know little about mycorrhiza, but it is probable that an excess of soil is not a disadvantage where this is concerned.
Where the acreage is large and the compost will not go round it all, it is probably better to give a medium dressing to a larger acreage than a heavy dressing to a smaller one. A dressing of about 5 tons to the acre is about the minimum for ordinary crops, but for such things as potatoes and truck crops at least 10 tons to the acre should be given, and, if available, considerably more. It must be borne in mind that much of the soil in Rhodesia has been so depleted of humus that in order to bring it properly to life again much heavier dressings of compost will be necessary now than when it has once attained natural conditions.
The more I see of compost-making the more necessary it appears to be to let the material have continuous access to air. This, as has been previously explained, can be done by frequent turning, and if turned quickly very little heat need be lost and no interruption in the process takes place.
An advance to better air-supply would be a series of brick flues under the heaps. :But under my conditions, with the position of the heaps continually changing and with Scotch carts and heavy wagons continually moving among the heaps, the flues would always be getting broken. Six-inch pipes with slots cut in the sides and the piece of metal from the slot hinged on one side and turned outwards on each side so as to form an air-space in the compost, with a continual supply of air from inside the pipe, would probably act quite well, the advantage being that such pipes would be portable and would be laid down just before the heap was about to be built. The disadvantage is, of course, one of cost. To go even farther, a small oil-driven compressor, such as is used to drive a pneumatic hammer, and mounted on a wheelbarrow or small hand-truck and connected to a pipe by rubber hose, could be used. The pipe would be, say, 1 inch in diameter and pointed at one end. For a distance of perhaps 18 inches from the point small holes would be drilled. The pipe would be pushed into the heap at the centre and air pumped in, the operation being repeated at perhaps distances of 3 feet. A large number of heaps could be treated with forced aeration in a day, and if this method resulted in the fixation of only a few extra pounds of nitrogen per ton it might be well worth while.
This is, however, perhaps going too far at the present stage. The great beauty of Sir Albert Howard's method is its simplicity. It can be used in native villages by primitive people using their own tools equally well as on the most up-to-date estates using elaborate machinery.
I am glad to say that the Rhodesian Government have laid it down that compost-making is to be taught at all native agricultural instructional centres. Interest in the matter will gradually awaken. I have already had old men from neighbouring villages come in to see how manure was made from dry grass.
We are on the eve of the compost era. Had its principles been applied years ago, the desolation that has taken place in the Middle Western States of America could have been avoided. The so-called 'law of diminishing returns' is seen to apply only to those who do not really understand the soil and treat it as Nature meant it to be treated. Rhodesia is fortunately a young country and the destruction of its soil has not gone very far, comparatively speaking.
If compost making becomes general, which means thorough rebuilding of the soil and so providing it with greater fertility, greater power to withstand droughts through its enhanced ability to absorb the rainfall, much of which now runs needlessly to the ocean, a great change in the agricultural outlook will take place. The present system, employed by many, of mining instead of farming the soil, of stimulating it to the last extent with artificials, and -- when it has been killed -- abandoning it, must be exchanged for real soil-building according to Nature's methods. Only in this way can disaster, examples of which can be seen all round, be avoided, and the land be made to produce what it was intended to produce before our too clever methods were employed upon it.
J. M. Moubray
Southern Rhodesia [Zimbabwe]
2 February 1939.