Soils have been used to produce food since man first began to inhabit the earth. Initially the farming was conducted with simple hand tools and crop yields were low. In the last 100 years there have been major changes in agriculture. In the more highly developed parts of the world, such as the USA and Western Europe, farming is now highly mechanised and improved methods of cultivating the soil, mechanisation and use of fertilisers have led to high levels of crop production. In other parts of the world, by contrast agriculture has progressed rather little due to a variety of reasons, including poverty and unsuitable climates, and yields are still very low and unreliable from year to year.
There are several important factors that determine whether and how a particular soil is suited to agricultural production. The prevailing climate is important because crops need air, light and rainfall. The general topography is important - it is difficult to manage and grow crops on steeply sloping land and soils on steep slopes are also prone to erosion. The soils themselves should be permeable, have good waterholding capacity, a good structure and be well supplied with nutrients. Initially agriculture developed on the best suited land but gradually farming has extended onto less suited land where conditions may include low rainfall, low nutrient content and sloping land.
In the case of natural vegetation such as wild flowers and woodlands, many of the nutrients are recycled, with dead remains being passed back into the soil where they are broken down and made available again to the plant. Such is not the case with crops. In the case of crops most of the plant is taken off the field as part of the harvest and there are relatively few crop remains to fall to the ground, decompose and return nutrients to the soil. Without some man-made additions, e.g. fertilizers, to replenish the nutrients crops would not grow well.