Effect of bulk density, water content and mechanical impedance of a soil on the penetration and elongation of soybean seminal root
1997
Sato, T. (Kochi Univ., Nankoku (Japan). Faculty of Agriculture) | Suzuki, T. | Nakano, M.
Laboratory experiments were conducted to evaluate soil physical properties on the elongation of soybean (Glycine max Merr.) root germinated in a seed bed and grown to the soil core. Soil cores having variable soil-water contents and dry bulk densities were prepared for the test of root elongation. Soil mechanical impedance strongly influenced root elongation at the initial stage of root penetration into the core. The elongation rate of a root penetrated into the soil core for 1 d was influenced by both the bulk density and soil mechanical impedance. A reduction in the air porosity under wet soil also hindered the elongation rate due to insufficient oxygen supply to the root. Dry bulk density influences root elongation through the supply of pore space, and it was the second dominant factor for elongation. As root can easily make its own pore space for elongation with increasing soil-water content, this was the third factor affecting elongation. The role of soil-water to maintain root pressure could not be confirmed from our short-term experiments. It can be concluded that mechanical impedance is the most appropriate expression for root elongation because it includes the effects of soil-water content and bulk density
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