|Animal Traction in Rainfed Agriculture in Africa and South America (GTZ, 1991, 311 p.)|
|E. Aspects of implement use|
2.1 Overview of implements
The descriptions of the implements are subdivided according to the following categories: soil preparation, sowing and application of fertilizer, weed control and harvesting. A distinction is made between soil preparation and seedbed preparation only when necessary. Mechanical weed control, also representing a kind of soil preparation, is treated separately, although the same implements are partially used for soil preparation and weed control, such as the ard, ridger and chisel plow or cultivator.
For further classification of soil-preparation implements two approaches are possible: according to design or to manner of operation.
For this treatise it appears appropriate to index the implements used for soil preparation according to manner of operation, since they are directly connected to the requirements of the respective location. Design is employed as a further criterion, but it is subordinate to the manner of operation. One can thus distinguish between:
- implements that operate symmetrically to the line of draft power, as the ard,
- implements that work assymmetrically, as the mouldboard plow,
- rotating implements such as the disk plow or disk harrow.
Implements that work symmetrically to the line of draft power and rotating implements mainly loosen and mix the soil, while the mouldboard plow primarily turns it. In the group of symmetrically working implements most belong to the category for soil preparation. These are:
- chisel plow and cultivator,
- shovel-type implements as the fuor.
Implements for both soil preparation and weed control are collectively considered under the term chisel plow. In the narrower sense the term chisel plow is used for deeper soil preparation with tines and superficial tilling with duckfoot, sweep shares, etc. (e.g. bico de pato; section G 2.4.4).
If the implements are employed for weed control, then the term cultivator is used. The fuor is treated in section G 2.4.2. Implements for harvesting are hardly used in rainfed cropping in the regions investigated. Merely the groundnut lifter plays a greater role (section F 3.4.5). The use of mowing implements for grain harvesting are conceivable. However, the introduction of such implements, which has been attempted in Senegal and Brazil, has to date been unsuccessful. Under the conditions in South Brazil, with a high technological level and the promotion of wheat cropping, this implement might be worthwhile for the farmers. It could increase labour productivity by a factor of 20. However, it is questionable whether the expected number of sales could be an incentive for the farm machinery manufacturers. Only then could they be purchased for an appropriate price. (Fabry, 1990)
Multipurpose toolbars are used in numerous quantities in West Africa, especially as chisel plows and cultivators. The larger equipment such as the Ariana (figure F 20) or the similarly designed Policultor 600 in Brazil have been distributed under the auspices of special development programmes or in training centres; there are only a limited number of them, however. The sales of the wheeled tool carrier (Polyculteur in West Africa or Policultor 1500 in Brazil) have been less encouraging (for the reasons see section F 3.4.7 and Starkey, 1988a). The policultors were manufactured by CEEMAG, but production has been discontinued. At present they are fabricated by APAC.
Harvesting implements and multipurpose toolbars are not treated in great detail here, but receive attention in the case studies.
2.2 Design and maintenance problems
Under tropical or subtropcial conditions as for example in South Brazil the implements must often work on fields having large quantities of organic matter (growth of fallow, weeds or harvest residues). The most frequent constraints in these regions are working in this mass and the resultingclogging.
A low weight of the implements is of importance where the plots are far apart or are located on slopes (e.g. at various altitude levels because of the distribution of risk) and the associated transport of the plow to the fields.
The transport of implements to the fields can be done in different ways:
- the farmer carries the implement (figure E 11),
- it can be loaded on the animal, the cart or a sled (also forked branch),
- it can be dragged.
Dragging frequently causes damage to the implement, also the handle can become bent. This leads to a imbalanced burden on the farmer during the work. Sometimes, the implement remains on the field, which can lead to rapid deterioration and theft of the parts.
The handles generally cannot be adjusted to the tallness of the farmer. This often leads to a unbalanced bodily load. In one region differences of the height of the seeder handles were found to be between 89 and 114 cm and the widths between 51 and 76 cm (Casao et al., 1987).
A key problem of the technical functioning of the implements is the bearings for rotating parts. Abrasion of the wheel bearing on mouldboard plows is frequently reported. A one-sided wheel mounting, as with the implements in Togo, brings negative results. Simple repairs done by farmers, e.g. replacing the axle with water pipes or wooden bars, become very difficult. A fork-type mounting is then recommended. Occasionally, the wheel has too small a diameter for the soil characteristics or the existing plant growth. Solid wheels and too small wheels clog easily in wet and heavy soils. Large-dimensioned spoke wheels would be more appropriate in this case.
The publications often suggest the use of a supporting skid as an alternative, but in practice they are seldom encountered.
Connections with bolts are also a risk factor regarding potential damage. Prior to the introduction of mouldboard plows the work was done manually or with traditional animal-drawn implements; now a new unknown technology has been introduced whose principles of functioning are not simply understood.
Moreover, suited tools are lacking (spanners etc.) and often the incorrect sizes or the wrong parts are delivered (Togo, Tanzania, Zimbabwe, Niger). Worn out parts then cannot be exchanged, rendering the work difficult. Therefore, the adjustment of seed covering scrapers, tines of cultivators or the regulation of fertilizer applicators should be designed to be altered without the use of spanners. In order to avoid a loss of bolts some joints should preferably be welded. The reason given by Kenyan farmers for the disappearance of bolts was "screw-eating dogs", which was one of the grounds for the failure of multipurpose implements (Neunher, 1984). The loss of a clamp bolt leads to the fixing of the working width of a cultivator with wooden wedges, as shown in an emergency repair of an adjustment in South Brazil
Seeders place the highest demands on manufacturing and maintenance in the regions investigated, because of the required precision for the many rotating parts.
Most of the implements are treated in the following sections, although some are discussed exclusively or in greater detail in conjunction with case studies because of their regional importance.