Actual and Relative Soil Air Permeability as Soil Physical Quality Index

Developing indices to evaluate soil physical quality can facilitate diagnosis and decision-making. In this context, intrinsic soil air permeability (Kair) is a physical parameter very sensitive to structural changes due to soil management. However, it is important to establish a standard Kair, considering a reference soil physical state. Thus, the present study proposes to create an index called relative soil air permeability (Kairr), taking as reference the physical state of maximum bulk density, obtained by normal Proctor test. Kairr is the ratio between compacted soil air permeability (Kairc) and actual soil air permeability (Kair). Kairr was evaluated using disturbed and undisturbed samples of a Latossolo and a Planossolo. The experimental design was completely randomized, with four treatments (T1-Latossolo 0-0.1 m; T2-Latossolo 0.1-0.2 m; T3-Planossolo 0-0.1 m and T4-Planossolo 0.1-0.2 m) and eight replicates. Kairr was equal to 0.1032 and 0.3547 in the Latossolo and to 0.4115 and 0.1923 in the Planossolo, in the 0-0.1 and 0.1-0.2 m layers, respectively. These characteristic values observed in both soils and layers are due to the management adopted in the area. In Latossolo, the use of medium harrow has made the 0.1-0.2 m layer more restrictive to air movement, whereas the Planossolo showed lower values of relative soil air permeability in the 0-0.1 m layer due to animal grazing, which has greater impact on the superficial portion of the soil.