Abstract
The efficiency of sources used for soil acidity correction depends on reactivity rate (RR) and neutralization power (NP), indicated by effective calcium carbonate (ECC). Few studies establish relative efficiency of reactivity (RER) for silicate particle-size fractions, therefore, the RER applied for lime are used. This study aimed to evaluate the reactivity of silicate materials affected by particle size throughout incubation periods in comparison to lime, and to calculate the RER for silicate particle-size fractions. Six correction sources were evaluated: three slags from distinct origins, dolomitic and calcitic lime separated into four particle-size fractions (2, 0.84, 0.30 and <0.30-mm sieves), and wollastonite, as an additional treatment. The treatments were applied to three soils with different texture classes. The dose of neutralizing material (calcium and magnesium oxides) was applied at equal quantities, and the only variation was the particle-size material. After a 90-day incubation period, the RER was calculated for each particle-size fraction, as well as the RR and ECC of each source. The neutralization of soil acidity of the same particle-size fraction for different sources showed distinct solubility and a distinct reaction between silicates and lime. The RER for slag were higher than the limits established by Brazilian legislation, indicating that the method used for limes should not be used for the slags studied here.
Highlights
Soil acidity is one of the major chemical attributes related to plant growth as it affects the occurrence of phytotoxic elements and the availability of most nutrients
This study aimed to evaluate the reactivity of silicate materials affected by particle size during incubation periods in comparison to lime reactivity, and to calculate the relative efficiency of reactivity (RER) for silicate particle-size fractions
Except for wollastonite, the sources were separated into four particle-size fractions established by Brazilian legislation for lime (Brasil, 2006), described as ABNT #10 - corresponding to particles retained by #10 sieve, with diameter > 2 mm; ABNT #20 - corresponding to particles sieved through #10, but not #20, with diameter between 2-0.84 mm; ABNT #50 - corresponding to particles sieved through #20, but not #50, with diameter between 0.84-0.30
Summary
Soil acidity is one of the major chemical attributes related to plant growth as it affects the occurrence of phytotoxic elements and the availability of most nutrients. Studies show that silicate materials have great potential to improve soil chemical characteristics, mainly by increasing the pH. SiO32- is the neutralizing agent in silicates, which reacts with water releasing OH- ions that neutralize H+ and Al3+ phytotoxic (Prado et al, 2001), increasing Ca, Mg and base saturation (Brassioli et al, 2009; Corrêa et al, 2009). Slags are a silicon source (Souza & Korndorfer 2010) as well as enhancing nutrient uptake by plants (Fonseca et al, 2011). Further information on these materials is required, especially related to RER for particle-size fractions
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