Transformation of soil hydraulic properties during the growth of green pea plants

Soil structure and the corresponding soil hydraulic properties of arable soils vary considerably over time due to soil consolidation, root growth, soil swelling and shrinking, etc. The effect of root biomass growth has rarely been studied. Therefore, this study focused on short-term changes of these properties after sowing the model plant. Soil taken from the surface horizon of a Haplic Chernozem was packed in plastic columns, in which green pea plants were grown for 41 days. Three undisturbed soil samples were taken always from one of the plastic columns 16, 23, 30, and 41 days after the sowing to obtain soil water retention and hydraulic conductivity curves, bulk density and porosity. Two undisturbed samples were also taken for micromorphological analyses to evaluate porosity detected on each image. Four plastic columns were always disassembled to analyze root masses in each column. Both porosity and saturated soil water content increased over time. The initially gradual shape of the soil water retention curves changed into step-like shape (i.e., shape parameters α and n decreased and increased, respectively). Saturated hydraulic conductivity decreased. Significant positive correlations were found between the root mass and porosity, saturated water content or water content at the inflection point of the retention curve. Other correlations between the root mass and soil characteristics were not statistically significant. However, the relatively high R values indicated the direct impact of root biomass on all parameters.