Center pivot irrigation in the context of "Plant cultivation"

Agriculture is the practice of cultivating the soil, planting, raising, and harvesting both food and non-food crops, as well as livestock production. Broader definitions also include forestry and aquaculture. Agriculture was a key factor in the rise of sedentary human civilization, whereby farming of domesticated plants and animals created food surpluses that enabled people to live in the cities. While humans started gathering grains at least 105,000 years ago, nascent farmers only began planting them around 11,500 years ago. Sheep, goats, pigs, and cattle were domesticated around 10,000 years ago. Plants were independently cultivated in at least 11 regions of the world. In the 20th century, industrial agriculture based on large-scale monocultures came to dominate agricultural output.

As of 2021, small farms, of which the vast majority are one hectare (about 2.5 acres) or smaller, produce about one-third of the world's food. Moreover, five of every six farms in the world consist of fewer than 2 hectares (4.9 acres) and take up only around 12% of all agricultural land. In terms of total land use, large farms are dominant. While only 1% of all farms globally are greater than 50 hectares (120 acres), they encompass more than 70% of the world's farmland. Further, nearly 40% of all global agricultural land is found on farms larger than 1,000 hectares (2,500 acres).

Center pivot irrigation in Saudi Arabia is typical of many isolated irrigation projects scattered throughout the arid and hyper-arid regions of the Earth. Nonrenewable fossil water is mined from depths as great as 1 km (3,000 ft), pumped to the surface, and distributed via large center pivot irrigation feeds. The circles of green irrigated vegetation may comprise a variety of agricultural commodities from alfalfa to wheat. Diameters of the normally circular fields range from a few hundred meters to as much as 3 km (1.9 mi).

The projects often trace out a narrow, sinuous, and seemingly random path. Actually, engineers generally seek ancient river channels now buried by the sand seas. The fossil waters mined in these projects accumulated during periods of wetter climate in the Pleistocene glacial epochs, between 10,000 and 2 million years ago, and are not being replenished under current climatic conditions. The projects, therefore, will have limited production as the reservoirs are drained.