Agriculture From Past Until Now

Agriculture includes cultivation of crops as tending of livestock for the purpose of production of food and fiber for humans. Mankind began to cultivate food crops about 10,000 years ago. Prior to that time, hunter-gatherers secured their food as they traveled in the nearby environment. When they observed some of the grains left behind at their campsites sprouting and growing to harvest, they began to cultivate these grains. From these humble beginnings agriculture began. Slash and burn, an early type of crop culture, remains today a truly sustainable agriculture, one that is independent of fossil fuel energy. In such a system, about ten hectares of productive land is held in fallow for each planted hectare. With this rotation system, a hectare is planted once every 20 years, allowing the soil to reaccumulate vital plant nutrients. Although the practice requires large acreages and large labor inputs, the crop yields are adequate. For example, corn with ample rainfall can yield about 2000 kilograms per hectare (kg/ha). over time, human labor in agriculture has decreased, first because of the use of animals and finally with machinery powered by fossil fuels. Currently, plentiful and economical fossil energy supports an era of machinery and agricultural chemicals. About 1000 liters of oil equivalent are used to produce a hectare of corn with a yield of 9,000 kg/ha. One-third of this energy is used to replace labor, one-third for fertilizers, and one-third for others.

Worldwide, more than 99.7% of human food (calories) comes from the land. Serious environmental impacts, such as soil erosion, water pollution from surface runoff, and pesticide pollution, result from fossil fuel-intensive agriculture. A critical need exists to assess fossil energy limits, the sustainability of agriculture, and the food needs of a rapidly growing world population.Humans began to cultivate food crops and domesticate livestock approximately 10,000 years ago. Prior to that time, hunter-gatherers secured their food as they traveled in the nearby environment. When they observed some of the grains left behind at their campsites sprouting and growing to harvest, they began to cultivate these grains. From these humble beginnings agriculture began.

Camels pulling plough in western Morocco north of Essaouira.
 Source: Michael Hogan Prehistory

Slash and burn, an early type of crop culture, remains today a widespread form of agriculture in developing countries, that is independent of fossil fuel energy. In such a system, about ten hectares of productive land is held in fallow for each planted hectare. With this rotation system, a hectare is planted once every 20 years, allowing the soil to reaccumulate vital plant nutrients. Although the practice requires large acreages and large labor inputs, the crop yields are adequate for a family unit. For example, corn with ample rainfallcan yield about 2000 kilograms per hectare (kg/ha).

Camels pulling plough in western Morocco north of Essaouira. Source: Michael Hogan Prehistory

Pollen core analysis and other forms of scientific research have revealed details of early human agricultural enterprises.  Some of the world regions with clearly defined agriculture as early as the early to mid  Holocene are the Nile Delta, (Boahen and Josephy, 1971) Mesopotamia, Indus Valley, China, Scandinavia, Orkney Islands, southern Europe and ancient Mauritania. As hunter-gatherer patterns transitioned to seasonal or permanent agricultural settlements, the human energy savings afforded by agricultural practices became translated into the first major public works projects of building elaborate structures of stone and mud-dried brick. By the later mid-Holocene (e.g. 5000 to 3000 years before present) advances in agricultural techniques spread by diffusion and innovation to more remote parts of Asia, the Mediterranean islands, the Americas and throughout the British Isles.There is evidence in disparate world regions that agriculture was practiced in non-sustainable fashions in some areas as early as the period 1400 to 4000 years before present; for example architectural and pollen core records in such locations as Creteand in the Mayan culture of Central America that fiber and food harvesting exceeded the local environment's capablity for time continuity of production.

Over time, human labor in agriculture has decreased, both due to the use of animals and later with machinery powered by fossil fuels. Currently, plentiful and economical fossil energy supports an era of machinery and agricultural chemicals. About 1000 liters of petroleum equivalent are used to produce a hectare of corn with a yield of 9000 kg/ha. One-third of this energy is used to replace labor, one-third forfertilizers, and one-third for others.

Polyculture of rice paddy/fish farming valley and
 benched upland crops. eastern madagascar.
Source: C Michael Hogan

Polyculture of rice paddy/fish farming valley and benched upland crops. eastern madagascar. Source: C Michael HoganAgricultural practices for crops can be classified as to cropping patterns, water management, tillage methods, nutrient supply, pest control and harvesting techniques. Cropping patterns consider such variables as seasonal or annual rotation, fallow periods, geometry of planted area, and monoculture versus polyculture planting. Choice among these patterns will affect the ability of soils to regenerate, the ability to sustain water supplies over an indefinite period and the total demand on external  resources needed to sustain the activity.For example soil regeneration of one centimeter in depth requires approximately one millennium.

Water management choices may involve selection of groundwater, surface water or unirrigated  strategies. Groundwater use is a method that must be very carefully constructed, since it may subject the aquifer to  overdraft, potentially leading to catastrophic cessation of water yields; this phenomenon is currently observable in parts of the western plains in the USA (House. 2006) and on the North China Plain, as well as numerous other world regions. Furthermore, groundwater extraction generally requires a very high energy input in order to pump water to the root zone.

Major crops

Biomass derived from plants is by far the most energy efficient way of delivering food to humans (or any omnivorous species). The limiting factors of producing such vegetative biomass are the processes of carbonand nitrogen fixation. Carbon fixation is chiefly conducted through photosynthesis, whereas nitrogen fixation in the natural environment is mainly conducted through symbiosis of certain host root systems with soil bacteria. Nitrogen fixation in vegetation normally produces ammonia, which in turn is used byplants to produce amino acids and proteins. Nitrogen fixation can also be accelerated by the very energy intensive industrial process of ammonia manufacture.

Photosynthetic biomass production is important in a large variety of basic foods including leafy vegetables, tubers and pulses. Nitrogen fixation is key in growth of legumes such as soybeans, lima beans, peanuts and kidney beans. Indirectly it is important for many other plants by producing nitrogen in the fallow cycle for such crops as alfalfa.

About half of the caloric intake of the human population derives from cereals. While these crops are relatively energy efficient to produce, the expansion of rice cultivation is placing an increasing pressure on water resources, a scarce commodity in today's world.