Phosphorus: Agricultural Nutrient

Authored by: John Ryan , Hayriye Ibrikci , Rolf Sommer , Abdul Rashid

Encyclopedia of Environmental Management

Print publication date:  December  2012
Online publication date:  December  2012

Print ISBN: 9781439829271
eBook ISBN: 9781351235860
Adobe ISBN:


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Of the nutrients that sustain terrestrial and aquatic life, phosphorus (P) is one of the most crucial. Total P in soils is relatively low and is a function of the rocks from which soils are derived. However, plant availability of P is only a tiny fraction of total soil P and is largely conditioned by the complex chemical reactions that occur between soluble P and soil constituents and the equilibrium that exists between various solid-phase P and solution P fractions. While natural ecosystems, forests, and native vegetation have evolved adaptation mechanisms to cope with low P availability, cultivated plants and crops are largely limited by P availability. Consequently, from the dawn of settled agriculture, adequate P nutrition has been a major constraint to optimum crop output and, thus, population growth. The development of inorganic P fertilizer, i.e., superphosphate, in the mid-19th century was a milestone for agriculture—and for mankind. The past century saw a rapid expansion in P fertilizer use, especially in developed countries. Commercial fertilizer use was largely responsible for increasing agriculture's bounty and contributing to world food stocks. However, because of profitability of P fertilizer use, helped in many cases by subsidies, overuse or excess of P increasingly became an issue, and that was exacerbated by the use of animal manure. Thus, in the past few decades, runoff from agriculture became a nonpoint source of P pollution of waterways and lakes, leading to eutrophication. The phenomenon of P pollution was particularly acute in Western Europe and in areas of the world with intensive agriculture and animal industries. Recognition of the implications of P pollution has led to legislation that restricted P use—and management strategies in response to such legislation. In essence, agriculture of today has to reconcile food and feed production with environmental protection. This brief review outlines the historical role of P in agriculture and the shifting orientation of concerns to include a consideration of the environmental research leading to societal awareness of P pollution along with specific approaches to mitigate the problem.

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