Other things being equal, farming output will therefore fall (or grow more slowly), depending on the elasticity of final demand. Farmers mechanize, although they can seldom prevent some increase in their production cost. The best example of these trends comes from the United States after 1940. The use of tractors, combines, and other machines expanded at unprecedented rates. Although labor input per acre or per animal had declined a little between 1915 and 1939, it fell sharply after 1940.
Regardless of the stage of mechanization, new power sources are always used first for power-intensive operations. Furthermore, it appears that the price of labor matters less for the mechanization of power-intensive operations than for control-intensive ones-that is, it often pays to move to a higher stage of mechanization in power-intensive operations, even at low wages, when mechanization of control-intensive operations is not profitable.
Using state-of-the-art technology, a well-maintained combine harvester operated effectively in a mature crop, can attain clean grain recoveries of 99 % – a remarkable achievement! Work rates in excess of one hectare (10 000 m 2 ) per hour are readily achievable with two operators, one to drive the combine, the other to drive a tractor-trailer or a truck into which the combine periodically empties its grain for transportation to the farm granary or direct to the local grain merchant or storage facility.Examples include herbicide application based on sensed soil organic matter content, and anhydrous ammonia application in growing maize based on sensed soil nitrate level. This is a complex technology that requires a major investment in research and development. The pay-off will derive from the savings accrued due to lower use of expensive agrochemicals, environmental protection and sustainability.Another interesting development pioneered in France is the robotic approach to harvesting tree fruit like apples and oranges where the mature fruit is selected by machine vision using light reflectance, picked mechanically by the robot and conveyed pneumatically (under vacuum) to a storage pallet. Whether these exciting but expensive technologies can be successfully commercialized remains to be seen. Gantry mechanization (including harvesting) of fruits and vegetables in greenhouses has also been investigated but cost remains a difficult factor to overcome.
The overall sequence of operations (Figure 8) is orientated towards protecting post-harvest product quality and minimizing loss due to deterioration occasioned by respiration, microbial activity, insects or rodents. Control of respiration (i.e. conversion of carbohydrates to carbon dioxide and water) in crop products is achieved by temperature reduction, most usually by refrigeration but also by periodic ventilation typically of the cold night air.