Agriculture is the process of producing food, feed, fiber and many other desired products by the cultivation of certain plants and the raising of domesticated animals (livestock).
The practice of agriculture is also known as "farming", while scientists, inventors and others devoted to improving farming methods and implements are also said to be engaged in agriculture.
Subsistence farming, who farms a small area with limited resource inputs, and produces only enough food to meet the needs of his/her family.
At the other end is commercial intensive agriculture, including industrial agriculture.
Such farming involves large fields and/or numbers of animals, large resource inputs (pesticides, fertilizers, etc.), and a high level of mechanization.
These operations generally attempt to maximize financial income from grain, produce, or livestock.
Modern agriculture extends well beyond the traditional production of food for humans and animal feeds.
Other agricultural production goods include timber, fertilizers, animal hides, leather, industrial chemicals (starch, sugar, alcohols and resins), fibers (cotton, wool, hemp, silk and flax), fuels (methane from biomass, ethanol, biodiesel), cut flowers, ornamental and nursery plants, tropical fish and birds for the pet trade, and both legal and illegal drugs (biopharmaceuticals, tobacco, marijuana, opium, cocaine).
The 20th Century saw massive changes in agricultural practice, particularly in agricultural chemistry.
Agricultural chemistry includes the application of chemical fertilizer, chemical insecticides, and chemical fungicides, soil makeup, analysis of agricultural products, and nutritional needs of farm animals.
Beginning in the Western world, the green revolution spread many of these changes to farms throughout the world, with varying success.
Other recent changes in agriculture include hydroponics, plant breeding, hybridization, gene manipulation, better management of soil nutrients, and improved weed control.
Genetic engineering has yielded crops which have capabilities beyond those of naturally occuring plants, such as higher yields and disease resistance.
Modified seeds germinate faster, and thus can be grown in an extended growing area.
Genetic engineering of plants has proven controversial, particularly in the case of herbicide-resistant plants.
As of 2006, an estimated 36 percent of the world's workers are employed in agriculture (down from 42% in 1996), making it by far the most common occupation.
However, the relative significance of farming has dropped steadily since the beginning of industrialization, and in 2006 – for the first time in history – the services sector overtook agriculture as the economic sector employing the most people worldwide.
Also, agricultural production accounts for less than five percent of the gross world product (an aggregate of all gross domestic products).