Most types of farming produce food for people to eat. Farmers make the best use they can of natural resources (such as soil and climate) to produce crops and rear animals. Different types of plants and animals need different conditions to grow well in and there is a variety of types of farming around the world. 　 Dairy farming and mixed farming Dairy farming produces milk, butter and cheese from cows that graze in grassy fields. Dairy farms are usually quite close to large cities so that fresh milk can quickly reach people’s kitchens. Mixed farming involves both crops and livestock. The main area is the corn-belt of the mid-west USA. Here farmers grow corn to feed pigs and cattle. Oats and hay are also grown as feed, as well as other crops such as soy beans and wheat. Mixed farming is found in Europe, too, in a region that stretches from northern Portugal and Spain across France, Germany and Poland and into Russia. In Britain mixed farms are found from Devon across the counties of the Midlands. Mediterranean farming is found in areas with a Mediterranean climate where winters are mild, summers long and dry and rainfall is quite low. These areas are around the Mediterranean Sea, and also in California, Chile, South Africa and Australia. Winter crops include wheat and barley. Summer crops include peaches, citrus fruits, tomatoes, grapes and olives. Shifting cultivation is a common type of farming in many tropical countries. It is different from settled farming because shifting cultivators raise crops in a place for only as long as the soil allows the crops to grow well. After a year or so in one place the farmer moves on, cuts the natural vegetation from another area, and leaves the first plot to return to its natural state. Shifting cultivation is practiced in the tropical forests of Central and South America, Africa and south-east Asia. Farmers grow maize, rice, manioc, yams, millet and other food crops. 　 Pastures and cattle ranges Much of the beef in hamburgers eaten in North America comes from cattle that graze in Central and South America. To expand cattle-ranching, tropical forests have been cut down to provide grasslands for "hamburger cattle". Cattle also graze on natural grasslands such as the pampas of Argentina, where cattle have been herded by "gauchos" on horseback for more than a hundred years. In countries where intensive farming is practiced, such as Britain, some cattle are not only fattened on pastures. They are also injected with drugs that make their bodies produce more meat. Where this is not done the farming is "extensive" rather than "intensive", as quite large areas of grassland are needed to fatten one cow. In parts of East Africa where grasslands are not good enough to feed cattle all the year round, farmers have to move their herds with the seasons to find new grasslands. 　 Farm animals Sheep, cattle, pigs, chickens and goats are all farm animals. Sheep are kept both for their meat and for their wool. A farmer or shepherd leaves sheep to graze on grasslands. Dogs often help to round up the sheep and to protect them and their lambs from wild animals such as wolves and eagles. Sheep are often reared on grasslands that cannot be used for other types of farming because they are too steep or too dry. Lamb and mutton are popular meats in many regions of the Middle East. You would rarely see pigs kept on farms in the Middle East, however, because most people there are Muslims and do not eat pork. Chickens are found on farms in many regions of the world. In Western Europe and North America large numbers of chickens are kept indoors in row upon row of small cages, often never seeing the light of day. The farmer feeds these "battery hens" each day and collects their eggs. 　 Intensive farming Battery hens are an example of intensive farming: farmers organize their animals and crops to get the maximum food from them. Intensive farming uses a lot of machinery to make it more efficient. Tractors are used to plough fields and plant seeds, and chemical fertilizers make plants grow stronger, while pesticides kill pests and herbicides kill weeds. In North America the wheat belt, stretching from the USA into the Canadian prairies, is a large area of intensive farming where the wheat is harvested with combine harvesters. 　 Grain farming Grain (cereals) is the most important food source for most people in the world. The main types of grain are wheat, corn (maize), and rice. The USA, Argentina, Australia and Russia are the main world areas of wheat production. Farming in these countries is mostly intensive. Farmers use machines, fertilizers, pesticides and herbicides on large wheat fields. This intensive farming means that the amount of grain produced from a hectare of field (its "yield") in North America is over four times that produced from a hectare in Africa. The USA is the world’s biggest exporter of grain. Nearly every African country imports grain. Grain is also used for animal fodder.　 The Green Revolution In the 1960s special international efforts were made to breed new crop varieties that would produce better yields. This would produce more food from an average field to feed the fast-growing populations of tropical countries. Scientists were successful in breeding high-yield types of wheat and rice. This has become known as the “Green Revolution”. In India, China, Mexico, the Philippines and other parts of south-east Asia the production of these foods has risen quickly. Some of the new rice types, for example, yield three times as much rice per hectare as traditional types. They also grow more quickly, allowing two or three crops a year from land that used to produce only one crop. There are problems, however. The new varieties of plants need fertilizers and pesticides if they are to grow well and resist diseases. Not all farmers can afford these chemicals, which also cause pollution of soil and water. 　 Organic farming Farmers who choose to farm organically do not use chemicals on their land. Fertilizers, pesticides and herbicides can cause problems. They kill plants and animals that the farmer does not want to kill, and very small traces of the chemicals may be left in crops, which may make them dangerous to eat. Organic farming uses compost and manure from farm animals to fertilize the land, and other plants, such as garlic, to control insects. Animals kept on organic farms are allowed to roam in the open air and are not locked up in cages for long periods. Organic farming has grown in the USA and Europe as farmers have realized some of the problems of intensive farming. Many people believe that food grown organically tastes better and is safer than food produced by intensive methods.　 Farms of the future Some of the problems of poor weather can be solved by breeding special new crops that are not so spoiled by frost or certain pests. This sort of breeding, using "plant genetics", is going to become more and more common in farming in the future. 1. In the corn-belt of the mid-west USA, the farmers ________.