|Environmental Handbook Volume II: Agriculture, Mining/Energy, Trade/Industry (GTZ, 1995, 736 p.)|
|33. Agricultural engineering|
2.1 Man, ecosystem and agricultural engineering
2.1.1 Man and agricultural engineering
Agricultural operations are generally mechanised for reasons of labour efficiency, namely
- to raise per-capita productivity (worker performance) and
- to reduce the burden imposed by physical labour.
The changeover to a different source of power - i.e. from manual labour to animal traction to motorisation - brings major new technical and economic factors into play. This means that operation, maintenance and management must all meet correspondingly higher standards.
While the burden of heavy physical labour is reduced, work may subsequently become one-sided or monotonous. Animals or machines determine the pace of the work. Noise prevents communication and can adversely affect health, as can engine exhaust emissions.
Operators and other people can be endangered if machines get out of control. Moving parts (shafts, belts, rods) increase the accident risk.
Operation of machinery generally enjoys higher status than manual labour or handling of animals. Mechanisation can lead to changes in the division of labour and distribution of income, with "women's work" becoming "men's work" (seldom the reverse).
The way in which technical aids are used is generally the crucial factor determining whether they have positive or negative impacts. As motorised techniques tend to magnify errors, however, such methods can have considerably more serious negative effects than may result, for example, when hand-held implements are used.
It is particularly important that the right equipment be selected for a particular operation and that machinery and implements be used properly and at the right time. This can be achieved above all by training and advising the operators and by imposing legislative requirements (accident prevention, technical inspection etc.).
2.1.2 Ecosystem and agricultural engineering
As the degree of mechanisation increases, cropping areas and roads and tracks are geared to the demands of the machines and implements. Use of tractors and self-propelled machines such as combine harvesters - or indeed even the use of animal traction - calls for large cropping areas, which should be as free as possible of obstacles such as stones, trees and tree stumps.
Intercropping - i.e. simultaneous cultivation of several different crops in a single field - offers few opportunities for mechanisation and single-cropping systems therefore predominate. Following tillage, the surface of the ground remains unprotected for several weeks and may be exposed to the risk of erosion by wind and water. Broadcast sowing is replaced by row seeding; rows which follow the slope of the terrain can increase the danger of erosion by water. Roads and bridges, as well as irrigation and drainage channels, are often designed to meet the requirements of mechanisation. Ecologically valuable areas such as forests, hedges and fallow land are increasingly lost.
The spectrum of flora and fauna in a region may be diminished or altered; ecological diversity is reduced. An absence of windbreak vegetation in arable-farming areas increases the risk of erosion by wind.
Top priority must be given to promoting mechanisable land use systems which take both economic (including labour efficiency) and ecological aspects into account. Such production and farming systems have already been designed for certain regions (particularly in temperate climates) and their use is to be encouraged. Applied research and development work is still needed in other regions. It is not enough, however, to provide purely technical training and advice on proper use of machinery and implements. A new awareness is required on the part of all concerned (from agricultural workers to decision-makers) if the inherent potential of mechanisation is to be utilised and risks are to be recognised and reduced.
It is important to preserve refuges, forests, hedges, wetlands and other niches for flora and fauna. Such areas do not hinder large-scale mechanised farming, as there are few labour-related advantages in having cropping areas larger than 20 hectares. Row seeding is essential in order to permit mechanical weed control techniques, for example, to be used instead of chemical methods.
2.2 Agricultural engineering in general
2.2.1 Energy sources, drive systems, fuels and lubricants
The principal sources of power are manual labour, animal traction and engines or motors. Wind and water power are used all over the world to drive stationary machines (mills and pumps).
In many countries, biomass (particularly wood, but also straw and dung) is the major source of energy for cooking in rural areas (see also environmental brief Renewable Sources of Energy).
The demands of agriculture may sometimes compete with those of rural households. If draught animals are kept, land must be used for cultivating forage crops and is thus not available for growing food; use of dung as fuel deprives the cropping area of nutrients; both stationary and mobile engines (e.g. those of tractors) are still fuelled for the most part by non-renewable forms of energy, particularly petroleum products.
As such engines are not required to power vehicles travelling long distances, they emit only limited quantities of nitrogen oxides and carbon monoxide. Use of clean fuel and correct engine tuning can nevertheless help to minimise harmful emissions.
Where internal combustion engines are used (e.g. in tractors and water pumps), surface water may be contaminated by fuels and lubricants. The risk is particularly high in parking areas and workshop yards where fuel tanks are filled and oil changes performed.
The technical facilities used for transporting and storing fuels and lubricants are often in need of improvement. Tanks must be checked for leaks and contamination. Oil collectors for use during oil changes are to be provided and a used-oil processing system is to be set up. Negligence in handling fuels and lubricants (which can create fire hazards and lead to contamination of soil and water) can be reduced only by means of long-term training measures and appropriate technical facilities. Efficient governmental or private monitoring institutions (e.g. like Germany's water authorities and technical inspectorates (T)) must be established.
Use of biodegradable oils is to be promoted. Where power saws (whose chains require a great deal of oil) are used in water conservation areas, for example, only vegetable-based lubricating oils (rape-seed oil) should be employed as is the case in Germany. This regulation is to be extended to cover hydraulic oils for vehicles operated in water conservation areas. It is recommended that use of such oils in agriculture also be encouraged.
2.2.2 Production of technical aids
Hand-held implements and simple animal-drawn implements are often made by the family wishing to use them or by local craftsmen. Such production activities have few if any environmental impacts. The comments made in the environmental brief Mechanical Engineering apply in the case of industrially manufactured agricultural machinery and implements.
2.3 Specific aspects of plant production
Loosening the soil with the aim of improving conditions for the crops plays a crucial part in arable farming. One purpose of turning the soil is to eliminate plants competing with the crop.
The extent to which the soil structure is changed depends on the form of tillage, which may involve
- loosening the soil with hooks or tines,
- turning the soil with the plough, or
- crumbling and breaking up the soil with a powered rotary cultivator or harrow.
If greater drive power becomes available, this may lead to selection of implements (e.g. rotary cultivator rather than plough) which modify the soil structure to a greater extent. In addition, less suitable (marginal) sites may be "put to the plough". Both of these steps increase the risk of soil degradation, which may involve reduction of pore volume, water absorption capacity and water storage capacity, the danger of puddling and crusting and a loss of organic matter. Crusting impedes water penetration and plant growth.
The optimum degree of soil moisture for tillage lies within narrow limits. If the soil is tilled when it is too wet it will be compacted, while tilling a soil which is too dry will result - depending on its clay content - in formation of clods or pulverisation. Compaction may assume sizeable dimensions if heavy tractors and implements are used.
Among other things, compaction of the soil has effects on plant growth, soil organisms and the availability and breakdown of plant nutrients and pesticides. On slopes, soil layers above the compacted horizon may slip.
Loosening of the soil and introduction of organic matter have positive impacts on the soil fauna. By contrast, compaction and puddling, frequent disturbance of the soil by tillage and application of pesticides and fertilisers all adversely affect the development of soil organisms.
Measures for preventing soil erosion and compaction include the following in particular:
- The soil should if possible have permanent vegetation cover in
the form of living crop plants (permanent cropping, intercropping, alley
cropping) or dead plants (mulch).
- Crops should be sown directly into the remnants of the preceding crop (without the soil being turned).
- Crop residues should be left on the surface and should not be ploughed under.
- Coarse soil structures are to be created or preserved through appropriate crop rotation measures and use of suitable implements.
- Contour ridges or terraces are to be created on slopes. This may be a somewhat complicated operation; there may be no vehicle access to the land in question.
- Windbreaks are to be planted at right angles to the direction of the prevailing wind.
- Organic matter is to be preserved and increased if possible.
- The pressure to which the soil is subjected when vehicles are driven over it is to be reduced as far as possible by using small/light-weight tractors and machines or larger tyres.
- Where possible, the soil should be driven over and tilled only when the moisture content is optimum.
- Shallow and deep tillage implements are to be used alternately over the course of time.
Emphasis must be placed on promoting a willingness to abandon excessive exploitation of the soil in favour of sustainable, site-appropriate forms of cultivation.
2.3.2 Sowing/planting, crop tending and fertilising
Sowing and planting, which are performed after the soil has been tilled, are intended to create optimum conditions for the growth of the seed or young plant.
After tillage, the soil may be totally or partly without cover until the crops have fully developed. It is thus exposed to the risks of erosion and to puddling as a result of heavy rainfall or severe evaporation.
With large cropping areas, mechanical aids are virtually essential for distributing chemical pesticides. Such equipment calls for highly skilled operators. Unsuitable, defective or incorrectly operated equipment can result in overdosage of fertilisers and pesticides, which will have negative effects on soil, plants and water as well as on the equipment users.
Application of highly concentrated liquid pesticides using the ULV (ultralow-volume) technique may lead to severe air pollution, with drift causing contamination over wide areas.
Pesticide users can be exposed to serious health hazards by touching or inhaling the chemical substances. It is often difficult to empty the containers completely and water used to rinse them out can contaminate surface water and drinking water. Pesticides and the equipment used to apply them are often stored improperly and are frequently kept in the same place as food for want of any other lockable rooms (see also the detailed remarks in the environmental brief Plant Protection).
Under unfavourable conditions, mechanical weed control measures (hoeing) can destroy the soil structure and encourage erosion; despite this fact, they should still be preferred to chemical methods.
Agricultural engineering can make a major contribution to ensuring that pesticides and fertilisers are used and applied correctly. Apart from selection of the right equipment, which is determined in part by the formulation of the agents used (e.g. powder or liquid), correct operation is equally important. If the time of application is appropriately chosen and economic-threshold concepts are used, quantities can be cut, drifting reduced and risks thereby minimised. Protective clothing, including face masks, is to be provided.
Under the climatic conditions prevailing in the tropics and subtropics, however, wearing of such clothing imposes considerable physical stress.
The stresses and risks for the equipment operators can be reduced to a large extent if the work is appropriately organised (e.g. operators proceed in the direction in which the wind is blowing).
2.3.3 Harvesting, threshing, processing, preservation, storage
The technical aids used in harvesting and threshing are intended to enable the work to be performed more easily and rapidly, besides minimising losses and risks. Harvesting and processing of "dry goods" (e.g. grain, burned-off sugar cane) can give rise to dust emissions which affect only a small area but are highly intensive. Such emissions affect people working and living in the vicinity, as well as animals. They can be reduced by taking technical measures at their source or their effects mitigated through the wearing of face masks and protective clothing.
Threshing and processing may yield by-products (glumes, hulls etc.). However, the quantities occurring at farm level do not constitute a serious environmental hazard, since the farm can generally utilise such products itself.
When crops are harvested, various substances are removed from the natural cycling systems on the site concerned. Efforts should be made to ensure that at least the by-products are returned to the soil either directly, after use for other purposes (e.g. as livestock fodder) or after composting.
Technical measures for preserving and storing produce at farm level seldom have any environmental impacts, unless chemicals are used. Crop drying calls for an energy supply, however, and in certain cases this may lead to over-use of local forest resources. Efforts to alleviate this problem should focus on ways of reducing energy consumption (heat sources).
2.3.4 Supplying and distributing water
To supplement the environmental brief Irrigation, attention must be drawn here to a number of important interrelationships and areas of overlap between these two sectors.
The water application and distribution system (gravity-flow method with open channels, pressure method with pipes or hoses) has a considerable influence on mechanisation:
- Channels determine the field size and bridges are needed to
- Small embankments and ditches in the field are damaged when driven over.
- Pipes have to be removed before a field can be tilled or urgent plant protection measures carried out.
2.4 Aspects of animal production
Pasture farming has always been the traditional form of livestock husbandry. The use of technical aids is confined to protective and security measures (pens etc.); the same applies to the keeping of small animals (e.g. poultry, rabbits, bees). It is not until livestock farming is intensified, with livestock kept in confinement, that technical aids become increasingly important. In industrialised countries where intensive animal husbandry is practised (particularly in Europe), technical equipment has come to play just as vital a role in livestock farming as it does in crop growing.
In poorly ventilated livestock housing, heat, dust and gases - particularly ammonia - can create stresses for both man and animal.
Sizeable quantities of ammonia can escape into the air when animal excrement is stored and applied to fields as manure. In industrialised countries, ammonia is one of the principal factors causing the gradual death of the forests in regions where intensive livestock husbandry is practised. One effective countermeasure is to make sure that solid or liquid manure is immediately worked into the soil.
Improper storage and spreading of animal manure can lead to over-fertilising (eutrophication) of both surface water and groundwater.
Protective measures must often focus first of all on bringing about changes in awareness, for only when this has been achieved can technical measures contribute to reducing negative environmental impacts. Animal excrement must be regarded and treated as a valuable fertiliser and not as waste. It is also important that this fertiliser be spread over the cropping area precisely in line with the plants' nutrient requirements. Only if such measures can be realised will it be possible to develop intensive livestock farming methods that are environmentally sound in the long term.