Agricultural mechanization has involved the partial or full replacement of human energy and animal-powered equipment (e.g. plows, seeders and harvesters) by engine-driven equipment. Most of this is tractor driven and to a lesser extent self-propelled equipment (including harvesters, sprayers, fertilizer applicators, planters and seeders). Agricultural mechanization has been pioneered in North America and Europe and more recently in Japan, and is now spreading rapidly throughout the world. Notwithstanding such progress, a significant element of human and animal powered mechanization remains, particularly in the poorer regions of the world. The dominant energy sources on conventional farms in the developed world are diesel oil (to power tractors and other self-propelled equipment) and electricity (to provide light, heat and refrigeration; and to power electric motors to run milking machines, animal feeding systems, ventilation fans, water supply and irrigation systems).
As such, sowing and fertilizing may be combined in one field operation, as is common in cereal production where semi-continuous bands of seeds and fertilizers are planted close together at shallow depths in closely spaced rows (typically 175 mm apart). Of course, the fertilizer may also be applied separately (from the seed) in a corn drill style applicator. Milling rice for home consumption can also be done over a long period, and in Asia it is common for a mill owner to 'rent' his machine to customers. Rental markets for land preparation, with the use of animals or tractors, were once common in the United States, when plows were scarce, and in Europe. Such rental markets are now common in Asia wherever tractors or power tillers have penetrated.