The creation of nitrogen cycles in derelict land

Abstract

Because of an almost total absence of N capital, nitrogen cycles in derelict land soils do not exist. If N fertilizer is added to newly established vegetation, growth will occur, but it ceases after a few months because of lack of any continued N supply from a mineralization cycle. A capital of N has to be built up in the soil. Studies of successional communities on china clay wastes suggest that the amount necessary to provide for the needs of a self-sustaining ecosystem is much less than the amounts found in well established ecosystems. Nevertheless, a minimum of approximately 1000 kg N ha -1 (with 700 kg ha -1 in the soil) is required in temperate climates. In land restoration programmes, if top soil is not replaced or an organic treatment such as sewage sludge used, this N capital must be built up, mainly by the use of legumes, which can readily accumulate 50-150 kgN ha -1 annually if provided with appropriate conditions. N cycling then will take place normally.