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Agriculture involves the
domestication of plants. Data from molecular and archaeological research generated over the past 15 years now makes it clear that agriculture began independently over a much larger area of the globe than was once thought, and included a diverse range of taxa. At least 11 regions of the Old and New World were involved as independent centers of origin, encompassing geographically isolated regions on most continents, but several more have been suggested. The earliest development was around 11,500 years ago separately in both the
Fertile crescent and at Chogha Golan in modern day Iran, where wild barley, wheat and lentils were cultivated and where domesticated forms of wheat appeared about 9,800 years ago. The
Fertile Crescent of
Western Asia,
Egypt and the
Indus Valley were sites of the earliest planned sowing and harvesting of crops which had previously been gathered in the wild. Independent development of agriculture occurred in northern and southern China, Africa's
Sahel,
New Guinea, parts of
India and several regions of the
Americas. Agricultural techniques such as
irrigation,
crop rotation, and application of
fertilizers were developed soon after the
Neolithic Revolution but have made significant strides in the past 200 years. The
Haber-Bosch method for synthesizing
ammonium nitrate fertilizer represented a major breakthrough and allowed
crop yields to overcome previous constraints.