log in

Soils for farming and food

A field of arable crops 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.

Oil-Seed Rape - a common sight in Britain 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.

This woodland has plenty of fallen trees, rotting down and returning nutrients to the soil. In the case of natural vegetation such as wild flowers and woodlands, many of the nutrients are recycled, with dead plant remains being passed directly back into the soil in-situ where they are broken down and made available again to other growing plants. This is not the case with crops; here most of the plant is removed from the field when it is harvested. Relatively few crop remains 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. Some farming techniques try to release as many nutrients in the soil as possible. In previous years it was a common sight to see burning stubble in fields, with the ash releasing nutrients to the soil. Other techniques such as 'direct drilling' and carefully managed rotations seek to retain the soil's health and vitality.