Cycling of nutrients and their utilisation by plants in agricultural ecosystems

This paper is concerned with reinterpretation of published data on efficiency of nutrient utilisation in agro-ecosystems. A close examination of nutrient cycles both under pastoral and arable farming in various countries shows conclusively that the utilisation of phosphorus and potassium in the majority of ecosystems is very high, more than 70% of the added and recycled and K being either utilised by plants or remaining in a chemical form available to plants. This conclusion is in conflict with the traditional belief that due to the process of large-scale P fixation the major part of the added P is fixed in the soil in compounds not available to plants.