Pore morphology changes under tillage and no-tillage practices

Abstract

The relative influence of biological and mechanical processes on the structure of cultivated soils was estimated by investigating the macroporosity of the surface layers of a silty soil during a maize growing season. The soil was subjected to different cultivation techniques (conventional tillage, moderate tillage, and no tillage) and fertilization modes (mineral or organic) for five years. A typological model was developed (i) to identify the macropores by 2D image analysis in undisturbed soil samples, and (ii) to characterize their morphology with two shape parameters (elongation and regularity indexes). Based on the three usual pore categories (tubular, planar and packing pores), five groups were defined with an additional distinction within the packing pore category (discrete, continuous and planar packing). This typology, as based on a set of images that reached the representative elementary area (REA), proved appropriate to describe the structural modifications linked to the crop management practices. It was shown that mechanical soil working produces 'continuous packing pores' whereas the absence of work induces 'discrete packing pores'. The study of the intra-annual 2 structural dynamics enabled the identification of the processes responsible for those modifications. With conventional tillage, the progressive substitution of continuous packing pores with discrete packing pores can be interpreted as the resumption of biological fragmentation after mechanical fragmentation (harrowing). Without management, the soil is only subjected to biological fragmentation, so neither quantitative nor morphological evolution of the macroporosity was observed during the growing season, with the soil structure depending more on spatial heterogeneity than on seasonal changes.

Response of soil structure and hydraulic conductivity to reduced tillage and animal manure in a temperate loamy soil

“…The greatest difference between tillage treatments in both layers corresponded to the area of large complex macropores. Hence, the smallest total macroporosity measured under untilled layers is primarily due to the smaller area of large complex macropores, which is in agreement with other studies (Pagliai et al ., ; Hubert et al ., ). The origin of large complex macropores was determined based on micromorphological observations.…”

Intervalo hídrico ótimo para avaliação da degradação física do solo

“…A qualidade física do solo é um termo relacionado com sua estrutura, e os danos causados pelo uso e manejo, como erosão, desertificação e suscetibilidade à compactação, são originários da sua degradação (Hubert et al, 2007). De acordo com Omuto (2008), a perda da qualidade física do solo é um processo gradual que se inicia com a deterioração da estrutura do solo e termina com a perda diferencial de partículas por meio da erosão.…”

Evaporação da água na superfície do solo em sistemas de plantio direto e preparo convencional

“…A variabilidade da evaporação entre sistemas de preparo do solo pode ser atribuída a dois fatores principais: o padrão de cobertura de palha na superfície e as alterações na estrutura porosa do solo (Hatfield et al, 2001;Yang & Yanful, 2002;Aydin et al, 2005;Hubert et al, 2007). A palha modifica a perda de água na superfície do solo por alterar a ação dos elementos meteorológicos que compõem a demanda evaporativa da atmosfera (Aydin et al, 2005;Chen et al, 2007), e também por formar uma espécie de camada isolante ao fluxo hídrico, por causa do ar que permanece relativamente parado dentro da camada de palha (Lemon, 1956).…”