Biocarvão como condicionador da qualidade física de solo com caráter coeso

Abstract

Horizons with cohesive character impose physical constraints on plant development, especially when near the soil surface. The genesis of cohesive character is related to temporary and reversible cementation by amorphous silica. The hypothesis of this study was that a dose of biochar derived from the pyrolysis of cashew processing waste, when applied to the soil, not only promotes soil particle flocculation and aggregation but also optimizes silicon adsorption, consequently reducing cohesion and improving the physical quality of horizons with cohesive character. To conduct the experiment, samples were collected from a Bt1 horizon (with cohesive characteristics) of an ARGISSOLO AMARELO Eutrocoeso típico in Fortaleza, CE. Then, test specimens were assembled using dry fine soil and biochar derived from the pyrolysis of cashew processing waste in the following treatments: 0, 5, 10, 20, and 40 Mg ha-1. All samples were subjected to ten wetting and drying cycles (one cycle per week). Traditional and rheometric physical properties were evaluated. The experimental design was completely randomized. The data were subjected to analysis of variance using the F-test and mean comparison using the Tukey test, both at a 5% significance level. Regression and correlation analysis were also conducted between the studied variables and the respective biochar doses. Finally, principal component analysis was performed to characterize the treatments, and cluster analysis was conducted to form groups of greater similarity. The analyses were carried out using the SAS® OnDemand for Academics platform. Compared to the control group, the highest biochar dose resulted in increased soil silicon adsorption capacity (+15.3%), total porosity (+1.9%), macroporosity (+15.3%), air permeability at 33 kPa (+20.7%) and saturated hydraulic conductivity (+25.8%); and reduction in bulk density (-0.8%), penetration resistance (-16.1%), tensile strength (-36.5%), deformation at the end of the linear viscoelastic range (-10.5%), shear stress at the end of the linear viscoelastic range (-10.5%), and maximum shear stress (-26.9%). It was concluded that the application of biochar derived from cashew processing waste pyrolysis promotes silicon adsorption, resulting in reduced cohesion and improved physical quality of soils with cohesive characteristics. A dose between 20 and 40 Mg ha-1 was found to be more effective in improving the physical quality of these soils.