Pedosphere 28(1): 44--58, 2018
ISSN 1002-0160/CN 32-1315/P
©2018 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Assessment of Potential Nutrient Release from Phosphate Rock and Dolostone for Application in Acid Soils
Rogério Borguete Alves RAFAEL1,2, María Luisa FERNÁNDEZ-MARCOS3, Stefania COCCO2, Maria Letizia RUELLO4, David C. WEINDORF5, Valeria CARDELLI2, Giuseppe CORTI2
1Department of Rural Engineering, University Eduardo Mondlane, 257 Maputo (Mozambique)
2Department of Agriculture, Food and Environmental Sciences, Università Politecnica delle Marche, 60131 Ancona (Italy)
3Department of Soil Science and Agricultural Chemistry, Universidad de Santiago de Compostela, 27002 Lugo (Spain)
4Department of Materials, Environmental Sciences and Urban Planning, Università Politecnica delle Marche, 60131 Ancona (Italy)
5Department of Plant and Soil Science, Texas Tech University, 79409 Lubbock (USA)
Corresponding Author:Rogério Borguete Alves RAFAEL
      Finding alternative local sources of plant nutrients is a practical, low-cost, and long-term strategy. In this study, laboratory column experiments were conducted in a completely randomized design to evaluate the feasibility of using phosphate rock and dolostone as fertilizers or acid-neutralizing agents for application in tropical acid soils. The dissolution rates of different particle-size fractions (0.063-0.25, 0.25-0.5, and 0.5-2 mm) of both rocks were studied by citric acid solution at pH 4 and 2 and water, with extraction times of 1, 3, 5, 7, 12, 24, 72, 144, 240, and 360 h. The results showed that the dissolution of both rocks depended on the particle size, leaching solution, and extraction time. The dissolution rate of rock-forming minerals increased as the specific surface area increased, corresponding to a decrease in particle size. In all cases, the release kinetics was characterized by two phases:1) a first stage of rapid release that lasted 24 h and would ensure short-term nutrient release, and 2) a second stage of slow release after 24 h, representing the long-term nutrient release efficiency. Both rocks were suitable as slow-release fertilizers in strongly acid soils and would ensure the replenishment of P, Ca, and Mg. A combination of fine and medium particle-size fractions should be used to ensure high nutrient-release efficiency. Much work could remain to determine the overall impact of considerable amounts of fresh rocks in soils.
Key Words:  citric acid,dissolution rate,leaching solution,particle-size fraction,release kinetics,slow-release fertilizer
Citation: Rafael R B A, Fernández-Marcos M L, Cocco S, Ruello M L, Weindorf D C, Cardelli V, Corti G. 2018. Assessment of potential nutrient release from phosphate rock and dolostone for application in acid soils. Pedosphere. 28(1):44-58.
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