The use of air‐filled porosity and intrinsic permeability to air to characterize structure of macropore space and saturated hydraulic conductivity of clay soils

Abstract

SUMMARY Intrinsic permeability to air of macropore space (ka) is related to macroporosity (ɛ) and organization of macropore space (O). Organization is defined as ka/ɛ. The use of ka for estimating saturated hydraulic conductivity (Ka) is also considered. The relationship between Log (O) and ɛ (Oɛ characteristic) can be used to describe changes to the macropore space of clay soils by amelioration and compaction. The effects of dominant macropore shape can also be identified and calculated as an empirical index of the efficiency of the pore organization E (E=log (O)/ɛ). Intrinsic permeability can then be related to E in a E:ka characteristic. Intrinsic permeability is the parameter most sensitive to structural change and E is mainly influenced by the dominant shapes of the macropores. Thus, the E:ka characteristic is suggested as a basis for studying differences in macropore space as may occur in response to external and internal stresses upon the soil and different systems of soil management, for example increases of packing pores by cultivation or of fissures by gypsum application and loss of packing pores by compaction. Empirical data indicate that Ks of the B horizons of Australian red‐brown earths can be estimated from ka of macropore space at a standard potential.

Qualidade física de um latossolo vermelho sob plantio direto submetido à descompactação mecânica e biológica

“…Assim, os logaritmos de K a foram utilizados para tornar as distribuições mais próximas da normalidade (Groenevelt et al, 1984;Ball et al, 1988;Blackwell et al, 1990). Apenas os potenciais mátricos a partir de -5,0 kPa foram utilizados na avaliação da permeabilidade ao ar e na estimativa dos índices de continuidade de poros, pois em condições de ψ m maiores (-0,5; -1,0; -2,0 e -3,0 kPa) o solo apresentou-se impermeável ou, em raras medições, com baixos valores de K a .…”

“…Portanto, a K a pode ser usada na avaliação das alterações na estrutura do solo causadas pelo seu manejo. A K a e a ε a têm sido relacionadas na tentativa de avaliar possíveis diferenças na geometria e continuidade dos poros resultantes das práticas de manejo adotadas (Blackwell et al, 1990). Ball (1981a,b) e Shtykov & Daishev (1986) encontraram correlação linear positiva, sendo satisfatória nas análises de regressão dos dados de K a e de ε a .…”

Aeration condition of a clayey oxisol under long-term no-tillage

“…The values of K a for each Ψm are presented in table 2. The statistical distribution of the K a values was non-normal so a log+1 transformation was applied to adjust the data distribution closer to normality and allow parametrical statistical tests (Blackwell et al, 1990).…”

“…The normality of the distributions of the values for Ɛ a , K a and K1 were evaluated by the Shapiro-Wilk test. When normal distribution was absent, a logarithmic transformation was applied to the data to adjust the distributions to normality (Blackwell et al, 1990). The correlations between log K a and BD, and log Ɛ a were assessed by the Pearson correlation test.…”

“…Ball (1981), Ball et al (1988) and McCarthy & Brown (1992) describe a direct relationship between K a and air-filled porosity (Ɛ a ). Ball et al (1988), Blackwell et al (1990), Dörner & Horn (2006) and Groenevelt et al (1984) used the relationships between K a and Ɛ a to estimate indexes of pore continuity that characterize functional changes in the soil pore system. In Brazil, Silva et al (2009) (Ball & Robertson, 1994;Rodrigues et al, 2011).…”