3.1 Root channels
The channel area in each type of soil was larger at a depth of 25 mm than in deeper layers (Figure 1A). At the depth of more than 225 mm, the channel area was small, and there was no significant difference among various types of soil.
In the 0-200 mm and 200-400 mm soil layers, the channel area below the plants grown in the medium (M-UP) and low salinity soil (L-UP) was significantly larger than in the other types of soil (p≤0.05) (Figure 1B). In soils with low and medium salinity, the difference in root channel area between soil under the plants and the inter-row soil was significant. However, in highly saline soils, the root channel area was similar between the soil under the plants (H-UP) and the inter-row soil (H-IR). In this study, the lowest ratio of the total channel area in 0-200 mm vs. 200-400 mm soil layer was in the inter-row on highly saline soil (H-IR, 4:3). A general trend of channel area in different soils at various soil depths was soil under the plants > inter-row soil, as well as moderate and low salinity soil > high salinity soil (Figure 1B).