Abstract
Knowledge of a rock's composition allows for inferences regarding several properties, ranging from its physical characteristics to its solubility. This study aimed to evaluate the use of different extractants to solubilize the K present in rocks as a potential source of nutrients and the effects of extractant contact time and temperature on rock solubilization. Samples of two rocks and a mineral concentrated from a granitic rock were treated with ammonium dihydrogen phosphate (NH4(H2PO4)), calcium dihydrogen phosphate (Ca(H2PO4)2), sodium hydroxide (NaOH) and water (control). Sample-extractant treatments were performed using a water bath shaker at temperatures of 25 and 50°C for periods of 3, 7, 10, 20, and 30 days. The amounts of K extracted from rocks using the extractants were in the following order: NH4H2PO4>Ca(HPO4)2>NaOH>water. The sequence of K release (ppm) based on the rocks studied was as follows: nepheline syenite>green banded argillite>concentrated biotite. Increasing the extractant contact time and temperature enhanced the solubilized K content.
Highlights
Stonemeal (Luz, Lapido-Loureiro, Sampaio, Castilhos, & Bezerra, 2010; Straaten, 2007) is defined as crushed rocks or materials containing naturally occurring soil fertilizers used as a soil amendment
The application of stonemeal to soils may represent an alternative to minimizing dependence on imported fertilizers in Brazil, which, in the specific case of potassium (K), is the world's fourth largest importer (Associação Nacional para a Difusão De Adubos e Corretivos Agrícolas (ANDA, 2012)
Major oxides were analyzed by Acme Analytical Laboratories Ltd. (Vancouver) using methods FullSuite 4A and 4B on a inductively coupled plasma emission spectrometer (ICP-ES)
Summary
Stonemeal (rocks for crops) (Luz, Lapido-Loureiro, Sampaio, Castilhos, & Bezerra, 2010; Straaten, 2007) is defined as crushed rocks or materials containing naturally occurring soil fertilizers used as a soil amendment. The application of stonemeal to soils may represent an alternative to minimizing dependence on imported fertilizers in Brazil, which, in the specific case of potassium (K), is the world's fourth largest importer (Associação Nacional para a Difusão De Adubos e Corretivos Agrícolas (ANDA, 2012). Whereas phosphatic rocks are feedstock for both conventional and unconventional phosphate fertilizers, potassium silicates, such as feldspars, biotite, phlogopite, and muscovite, and rocks with feldspathoids, such as leucite, nepheline and clayrich sediments, especially illite, are the basis for alternative potassium fertilization (Straaten, 2010).
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