Modelling air conductivity function of unsaturated root-permeated soil

Air conductivity as a function of degree of saturation, k_a(S_w), is a crucial air transport parameter of soil to evaluate soil aeration. This function controls the level of oxygen stresses introduced to plants. It has been found that plant roots affect k_a(S_w) of soil where they grow in the soil pore space. However, there is no model available to predict k_a(S_w) of root-permeated soils. Quantifying the effects of plant roots on k_a(S_w) is vital to understand soil aeration. This study aims to derive a new model for the prediction of the k_a(S_w) of unsaturated root-permeated soils. Then a verification experiment was conducted, aiming to validate the new model by comparing k_a(S_w) predicted by the new model with k_a(S_w) measured in the experiments. In the experiments, k_a(S_w) of a compacted sandy loam vegetated with two grass species (Chrysopogon zizanioides and Cynodon dactylon) with different root densities was measured. The results showed that the proposed model predicts the k_a(S_w) of root-permeated soils of various root densities well.