A Review of the Role of Vehicles in Agriculture

Abstract

Agricultural tractors have been developed over the years to carry out almost every operation on the farm. However, they are not ideally suited to all these tasks and it may be more economical, in certain situations, to use more specialized vehicles. In the extreme, one could perhaps imagine four different types of agricultural vehicles, for heavy draught work, transport, low ground pressure applications and materials handling. Computer models are being developed to evaluate the potential economic benefits that might be achieved by the introduction of such specialized vehicles on particular farms. Models already exist for predicting tractive performance and average speed over different types of terrain. Further models are needed for manoeuvrability and some other aspects of performance. Mechanization of farming throughout the world has been based on the agricultural tractor. Introduced originally as a replacement for draught animals, it has now been adapted to carry out almost every job on the farm. Nevertheless, it is still the requirement to pull ploughs and other cultivation implements that mainly determines its design specification. This has led to the development of a slow, heavy, unsprung vehicle with large diameter, low inflation pressure driving wheel tyres. This design, with two driving wheels at the rear for the lower power ranges and all four wheels driven for higher powers, is reasonably well suited to carrying out heavy draught operations in the field while maintaining sufficient mobility to be useful for other jobs. The range of other jobs for which the agricultural tractor has been adapted has increased steadily over the years so that it would not be difficult to list perhaps forty or fifty. As far as their effect on the vehicle design specification is concerned, however, they can be grouped into relatively few classifications. Apart from cultivations, they comprise operations where transport of large quantities of materials is an important component—operations such as harvesting, spraying and fertilizer distribution, where neither tractive effort nor transport of materials is a major part, and materials handling. Obviously these are not strictly defined categories and many tasks will contain some elements of two or more of these classifications. However, they are useful in considering the design specifications for agricultural vehicles.