Aggregation of subtropical soil under liming: a study using laser diffraction

Abstract

Laser diffraction (LD) provides detailed analysis of particle size distribution. Its application to testing the stability of soil aggregates can assist studies on the aggregation of soils with contrasting electrochemical properties. The objectives of the present work were: (a) to propose a protocol for using LD to study soil aggregation, (b) to study the aggregation of an Acrisol under the influence of different doses and forms of lime. Samples were collected in 2005 from a Brazilian Acrisol that in 1994 had received 0.0; 2.0; 8.5 and 17.0 Mg ha-1 of lime, left on the soil surface or incorporated. Aggregates from 4.76 to 8.00 mm diameters were studied using the traditional method proposed by Kemper & Chepil (1965), with wet sieving, while aggregates from 1.00 to 2.00 mm were studied using a CILAS® laser diffractometer that distinguishes particles ranging from 0.04 to 2,500.00 μm. LD readings were made after six consecutive pre-treatments, using agitation times, a chemical dispersion agent and ultrasound. Mean Weighted Diameter (MWD) and the Aggregate Stability Index (ASI) calculated, using the traditional method does not discriminate the treatments. However, LD is able to produce detailed data on soil aggregation, resulting in indexes of stability of aggregates that are linearly related to the doses of lime applied (MWD: R² = 0.986 and ASI: R² = 0.876). It may be concluded that electrochemical changes in the Brazilian Acrisol resulting from incorporated lime affect the stability of aggregates, increasing stability with increased doses of lime.

Changes in Soil Physical Properties and Carbon Protection Mechanisms by Surface Application of Lime in a Tropical No‐Tillage System

“…These results can be explained by the lower TOC at subsoil layers compared with layers above a depth of 0.20 m. According to results obtained by Carter (1992), interactions between soil granulometric composition and microbial biomass as well as the level and quality of OC could define the structural stability, resulting in variations in the aggregate stability index. In an experiment similarly conducted for 12 yr on soil under no‐till conditions, Bortoluzzi et al (2010) reported that the MWD and stability index data presented negative coefficients of correlation for the sum of bases in the soil; thus, the application of high rates of lime promoted a decrease in these parameters.…”

Soybean root growth and crop yield in reponse to liming at the beginning of a no-tillage system

“…WMD and GMD values were lower in the 10-20 cm layer compared to the other layers, and lime application presented no effect on these properties compared to the control. This may be due to the low sensitivity of the method proposed by Kemper & Chepil (Kemper & Chepil,l965) in estimation of soil microaggregation (Bortoluzzi et al, 2010). RP values differed among the depths evaluated but did not go beyond the value of 1,837 kPa.…”

Propriedades físicas do solo em sistemas de rotação de culturas conforme o uso de corretivos da acidez

“…Assim, os benefícios proporcionados pelos corretivos à produção de matéria seca, durante as duas safras agrícolas (Tabela 2), pode ter minimizado o efeito deletério da dispersão da argila, que teria culminado na redução da macroporosidade (Tabela 3). Neste sentido, Bortoluzzi et al (2008Bortoluzzi et al ( , 2010 relataram melhorias nos atributos físicos em solos que receberam corretivos da acidez. Pértile (2011), ao avaliar o efeito de calcário e resíduo alcalino da indústria de celulose, como corretivos da acidez, nos atributos físicos e químicos do solo, não constatou interferência desses insumos na estrutura do solo, e sim melhorias químicas no perfil do solo, que proporcionaram maior crescimento das raízes do feijoeiro.…”