ABSTRACT: This ageing process was due to a shaking artifact (30%), microbial immobilization (57%), and sorption of P onto the soil in a non-oxalate accessible form (13%). Liming and organic anion loading improved P bioavailability in this Brazilian soil. Long-term ageing and continuous exudation of organic anions also influence P bioavailability. Management options that recognize this will improve bioavailability of native and applied P sources in this important agricultural region of northeastern Brazil.

Most reported incidents of soil contamination include an array of heavy metals species rather than a single ion. The various interactions in these multicomponent or multiple-ion systems significantly impact the fate and transport of heavy metals, and competition for sorption sites on soil matrix surfaces is a common phenomenon. Because of this, con

Advances in Agronomy continues to be recognized as a leading reference and first-rate source for the latest research in agronomy. Each volume contains an eclectic group of reviews by leading scientists throughout the world. As always, the subjects covered are rich, varied, and exemplary of the abundant subject matter addressed by this long-running serial. - Includes numerous, timely, state-of-the-art reviews on the latest advancements in agronomy - Features distinguished, well recognized authors from around the world - Builds upon this venerable and iconic review series - Covers the extensive variety and breadth of subject matter in the crop and soil sciences

Probably more than any other element, iron markedly influences the chemical and physical properties of soils and sediments in the earth. Considering its transition metal status, with potential variation in electronic configuration, ionic radius, and magnetic moment, combined with its abundance and relatively large mass, little wonder that one sees its unique influence on every hand. Pre sentations at the NATO Advanced Study Institute (NATO AS!) on Iron in Soils and Clay Minerals reviewed and discussed the occurrence, behavior, and properties of Fe-bearing minerals found in soils and in the clay mineral groups kaolinite, smectite, and mica. Also discussed at the NATO AS! were the basic chemical properties of Fe, methods for separating and identifying Fe in minerals, and the role of Fe minerals in weathering and other soil-forming processes. The present publication is the reviewed and edited proceedings of that Advanced Study Institute. The sequence of chapters follows the general pattern beginning with introductory chapters which overview the general occurrence of Fe in the earth and its chemistry, both generally and in mineral environments, followed by identification and characterization methods for Fe and Fe phases in minerals. The properties and behavior of Fe oxides, Fe-bearing clay minerals, and other Fe minerals in soils are then described, and the text ends with a summary of the role of Fe in soil-forming processes. A Table of Contents and subject index are provided to assist the reader in finding specific topics within the text.