Sabtu, 19 November 2011

Modern farming

New energy sources and three intertwined strands of innovation explain most of the success of modern farming. In contrast to traditional agriculture's, nonrenewable fossil fuels and electricity are essential inputs in modern farming. They are needed to build and operate agriculture machinery whose nearly universal adoption mechanized virtually all field and crop-processing tasks. The second key innovation is the use of fossil energies and electricity to extract and synthesize fertilizers and pesticides. The third key advance was to develop and diffuse new crop varieties responsive to higher inputs of water and nutrients. These innovations brought higher and more reliable yields, they displaced draft animals in all rich countries and greatly reduced their importance in the poor ones. The replacement of muscles by internal combustion engines and electric motors and the substitution of organic recycling by inorganic fertilizers have drastically cut labor needs in agriculture and led to huge declines in rural populations and to the worldwide rise of urbanization. For example, in the US rural labor fell from more than 60% of the total workforce in 1850 to less than 40% in 1900, 15% in 1950, and a mere 2% since 1975 (US Bureau of the Census, 1975).
 Fertilizers made the earliest, and also the greatest, difference. The use of chemically treated phosphates became common after the discoveries of new rock deposits in Florida in 1888, and in Morocco in 1913. After 1850 nitrogen from Chilean nitrates, supplemented later by the recovery of ammonium sulfate from coking ovens, provided the first inorganic alternative to organic recycling. The nitrogen barrier was finally bro-ken by the invention of ammonia synthesis from its elements by Fritz Haber and the sub-sequent rapid commercialization of the process by Carl Bosch (Smil, 2001).
This invention allowed, for the first time in history, to optimize nitrogen inputs on large scale. Modern civilization is now critically dependent on the Haber–Bosch synthesis of ammonia. Recent global applications of nitrogen fertilizers to field crops – and also to permanent grasslands and tree (orchard, palm) and shrub (coffee, tea) plantations – have been in excess of 80 million tonnes (Mt) N/year, mostly in the form of urea (IFA, 2001; Fig. 3.2). The process currently provides the means of survival for about 40% of the world’s population. Only half as many people as are alive today could be supplied.
1950 1960 1970 1980 1990 2000
Figure 3.2
Post-1950 growth of nitrogen fertilizer production.

By traditional cultivation lacking any synthetic fertilizers and producing very basic, and overwhelmingly vegetarian, diets; and prefertilizer farming could provide today’s average diets to only about 40% of the existing population (Smil, 2001). Western nations, using most of their crop production for feed, could easily reduce their dependence on synthetic nitrogen by lowering their high meat consumption. Populous poor countries, where all but a small share of grain is eaten directly, do not have that option. Most notably, synthetic nitrogen provides about 75% of all inputs in China. With some 75% of the country’s protein supplied by crops, more than half of all nitrogen in China’s food comes from synthetic fertilizers.
In addition to nitrogen the world’s crops now receive also close to 15 Mt of phosphorus, and about 18 Mt of potassium a year (IFA, 2001). This massive use of fertilizers has been accompanied by the expanding use of herbicides used to control weeds, and pesticides to lessen insect and fungal infestations. Pesticide use has often been much maligned and many of these chemicals, especially following improper applications, undoubtedly leave undesirable residues in harvested products, but their use has helped to reduce the still excessively large preharvest losses.
Farming mechanization was first accomplished in the US and Canada. Its most obvious consequence was the precipitous decline in agricultural labor requirements. For example, in 1850 an average hectare of the US wheat needed about 100 hours of labor; by 1900 the rate was less than 40 hours/ha, and 50 years later it sank below 2 hours/ha (US Bureau of the Census, 1975). Until the 1950s agricultural mechanization proceeded much more slowly in Europe, and in the populous countries of Asia and Latin America it really started only during the 1960s. Today’s agriculture operates with more than 26 million tractors of which about 7 million are in developing countries (FAO, 2001). Mechanization also completely transformed crop processing tasks (threshing, oil pressing, etc.) and fuel and electric pumps greatly extended field irrigation. The global extent of crop irrigation more than quintupled between 1900 and 2000, from less than 50 to more than 270 million hectares, or from less than 5% to about 19% of the world’s harvested cropland (FAO, 2001). Half of this area is irrigated with pumped water, and about 70% is in Asia.
The key attribute common to all new high-yielding varieties (HYV) is their higher harvest index, that is the redistribution of photosynthate from stalks and stems to harvested grain or roots. Straw:grain ratio of wheat or rice was commonly above 2:1 in traditional cultivars, whereas today’s typical ratio is just 1:1 (Smil, 1999b). HYVs receiving adequate fertilization, irrigation, and protection against pests did responded with much increased yields. This combination of new agronomic practices, introduced during the 1960s, became widely known as the Green Revolution and the term is not a misnomer as the gains rose very rapidly after the introduction of these rewarding, but energy-intensive, measures. Higher reliance on intensively cultivated grain monocultures, narrowing of the genetic base in cropping and environmental impacts of agricultural chemicals have been the most discussed worrisome consequence of this innovation, but all of these concerns can be addressed by better agronomic practices (Smil, 2000).
Aggregate achievements of modern farming have been impressive. Between 1900 and 2000 the world’s cultivated area expanded by about one-third, but the global crop
Figure 3.3
Post-1950 growth of average cereal grain yields epitomizing the rising productivity of modern
farming (plotted from data in FAO, 2001) 

Harvest rose nearly six fold. This was because of a more than fourfold increase of ave-rage crop yields made possible by a more than 80-fold increase of energy inputs to field farming (Smil, 2000). But even though the global mean harvest of all cereals more than doubled between 1950 and 2000 (Fig. 3.3), there are still large gaps between average yields and best (not record) harvests (FAO, 2001). Global corn harvest aver-ages just over 4 t/ha but farmers in Iowa are bringing in close to 10 t/ha. Average wheat yield (spring and winter varieties) is 2.7 t/ha but even national averages in the UK, the Netherlands or Denmark Western are more than 8 t/ha today. Extensive diffusion of HYV of rice raised the global mean yield to almost 4t/ha, whereas Japan or China’s Jiangsu average in excess of 6t/ha.
Higher cereal and tuber yields freed more agricultural land for no staple species, above all for oil and sugar crops. Higher cereal yields have also allowed for more and more efficient animal feeding in rich countries where the abundance of meat and dairy products has made high-protein diets much more affordable. HYVs also raised the food output of many developing countries above subsistence minima. However, a substantial gap still divides the typical agricultural performances of rich and poor countries, and, given the far greater social inequalities in the latter group, this production disparity translates readily into continuing large-scale presence of malnutrition in scores of African, Asian, and Latin American countries.


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Methods of Modern Farming

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