The image of a multiplicity of combine harvesters traversing and harvesting the corn plains of North America is a powerful testament to the success of agricultural mechanization programs. Developments in control and instrumentation have also been notable including wellestablished innovations such as grain loss meters, work rate meters and crop density meters.
More recently, direct drilling operations have become more popular where the seed is planted directly into non-cultivated soil using a corn drill (Figure 5) typically for winter cereals and forage crops, or a vacuum precision drill typically for maize, soybean and sunflower.
Energy conservation and reduced soil compaction are evident advantages of a system that can also combine two, three or four field operations into one.The operations of farming for which machines are used are diverse.
For crop production they include handling of residues from previous crops; primary and secondary tillage of the soil; fertilizer distribution and application; seeding, planting, and transplanting; cultivation; pest control; harvesting; transportation; storage; premarketing processing; drainage; irrigation and erosion control; and water conservation.
The abundance of plant pests in the tropics, including weeds and disease, makes agriculture successful mainly in the plantation system, where needed control measures can be financed. The alternative is to move from deteriorated land to newer fields; this practice of shifting agriculture has also been common, because tropical soils lose their productive capacity so rapidly.