In the economically developed world, most all farming is commercial. Farmers produce crops and livestock products for sale to make a profit. In the economically developing world farmers and their families grow crops mainly for their own consumption. What's left may be sold or traded for other products in local markets. We often call this type of self-sufficient farming -subsistence agriculture.
Farmers practice different kinds of subsistence farming, based upon their needs and locations. Farmers in the densely populated river alleys of India, the People's Republic of China, and Southeast Asia use intensive subsistence farming, planting as much food as possible on any lands that will support crops. Shifting cultivation is the traditional method of farming in the tropical rainforest. It is a form of subsistence agriculture, often combined with hunting and gathering practiced by small tribal groups. The rainforest has very poor soils – so poor that permanent cultivation is impossible. Shifting cultivators make temporary clearings in the forest. The ash from the burnt vegetation fertilizes the soil and allows cultivation for up to two years. Initially yields are good. However, cropping (farming without rotating crops) and heavy rainfall quickly remove plant nutrients from the soil, and it loses fertility. After two years, cultivation is no longer worthwhile; the plots are abandoned and fresh clearings are made in the forest. Shifting cultivation is a sustainable type of farming. This means that it does no long-term damage to the environment, if the intervals between cultivation are long enough to allow the forest trees to regenerate and the soil to recover its fertility.
Commercial farming differs in many ways from subsistence farming. Commercial farming can be either mixed or specialized Between 5 and 10 percent of the commercial farmers practice mixed farming, raising several different crops and animals for income. Mixed farming has several important benefits. Growing different crops allows farmers to alternate (rotate) crops in the fields. This practice of crop rotation replaces nutrients that in-previous crops took from the soil. Economically, growing different crops makes farmers less vulnerable to falling prices for farming products.
Most commercial farmers practice specialized farming, raisinga single cash crop or kind of animal for income. Specialized commercial farmers on plantations and very large farms raise most of the world's cotton, wheat, cattle, sheep, dairy products, poultry, rice, sugarcane, pineapples, bananas, tobacco, coffee and tea.