Morphological and Micromorphological Changes in the Structure of a Rhodic Hapludox as a Result of Agricultural Management

Abstract

In evaluation of soil quality for agricultural use, soil structure is one of the most important properties, which is influenced not only by climate, biological activity, and management practices but also by mechanical and physico-chemical forces acting in the soil. The purpose of this study was to evaluate the influence of conventional agricultural management on the structure and microstructure of a Latossolo Vermelho distroférrico típico (Rhodic Hapludox) in an experimental area planted to maize. Soil morphology was described using the crop profile method by identifying the distinct structural volumes called Morphologically Homogeneous Units (MHUs). For comparison, we also described a profile in an adjacent area without agricultural use and under natural regrowth referred to as Memory. We took undisturbed samples from the main MHUs so as to form thin sections and blocks of soil for micromorphological and micromorphometrical analyses. Results from the application of the crop profile method showed the occurrence of the following structural types: loose (L), fragmented (F) and continuous (C) in both profiles analyzed. In the Memory soil profile, the fragmented structures were classified as Fptμ∆+tf and Fmt∆μ, whose micromorphology shows an enaulic-porphyric (porous) relative distribution with a great deal of biological activity as indicated by the presence of vughs and channels. Lower down, from 0.20 to 0.35 m, there was a continuous soil volume (sub-type C∆μ), with a subangular block microstructure and an enaulic-porphyric relative distribution, though in this case more compact and with aggregate

Is Structural Quality as Assessed by the "Profil Cultural" Method Related to Quantitative Indicators of Soil Physical Quality?

“…The volumes of C soil are characterised by a lower volume of roots and lower biological activity in relation to the volumes of F soil (Fregonezi et al, 2001;Silva et al, 2014a;Silva et al, 2015). The internal state Δ comes from degradation of the structure by heavy machinery and indicates a compacted structure that strongly restricts root development (Neves et al, 2003;Ralisch et al, 2010) and is characterized by the absence of visible porosity.…”

“…The internal states Δμ and μΔ are intermediate with respect to Δ (compacted) and μ (noncompacted). The Δμ indicates a compact structure, but shows few visible pores; μΔ shows signs of anthropogenic action, but with visible pores (Silva et al, 2015).…”

“…, Cardoso et al (2006), andSilva et al (2015) demonstrated less root volume in the continuous C structures than in structures with fissures (F). According to Cardoso et al (2006), for a PR of 3 MPa, the soybean crop exhibited a root volume three times The LLWR for the soil and crop management treatments is shown in figure 3.…”

“…Studies have shown that structures identified through the PCM correlate with quantitative soil physical properties such as porosity (Silva et al, 2015), Bd and porosity of aggregates (Neves et al, 2003), and root growth (Cardoso et al, 2006).…”

Soil microstructure alterations induced by land use change for sugarcane expansion in Brazil

“…bulk density, soil porosity, soil penetration resistance and soil aggregation) along with visual assessment methods can efficiently infer the stability, and even resilience of soil structure (Castioni et al., ; Cherubin, Karlen, Franco, et al., ; Cherubin et al., ), these methods cannot reveal the precise spatial arrangement of soil structure and the geometrical form of pores and aggregates. Imaging methods, such as micromorphology, can be used to further study the dynamics of soil structural development across the time and/or space and help improve understanding concerning the impact of soil structure on soil functioning (Guimarães, Ball, Tormena, Giarola, & Silva, ; Pires et al., ; Silva, Marinho, Matsura, Cooper, & Ralisch, ; Souza, Souza, Cooper, & Tormena, ). Whilst other imaging methods such as X‐ray computed tomography (CT) have become more popular for the analysis of soil pore space in recent years, particularly as they facilitate faster acquisition of images and 3D visualisation, micromorphology is still an important technique for the analysis of soil structure as it permits the microscopic visualization of some soil properties, such as those derived from organic matter, for example faecal deposits, that are currently not straightforward to image by X‐ray CT (Helliwell et al., ).…”