The Effects of Major Organic Compound Found in Roots and Biological Exudates Influencing Liquid Transport in Soil

Soil organisms produce a range of exudates that may affect water uptake and transport by inducing hydrophobicity, clogging of pores or acting as a surfactant. Using the Capillary Rise Method, the rate of liquid uptake of a range of biological exudates were measured in model sands of varying texture and a range of soils with differing water repellency. The hypothesis was that root exudate compounds will counteract water repellency. The compounds examined were malic acid, malonic acid and oxalic acid, which are common components of root exudates, in addition to xanthan produced by bacteria. The results demonstrate that agricultural soil, Culbin forest, is extremely hydrophobic. Both fine sand and Glass Ballotini Contact Angle ( = 0) are completely wettable. Coarse sand texture is hydrophobic and silica flour is moderately. Sorptivity of Ethanol is large in Culbin forest; bullion field and Insch soil are less. Sorptivity of malonic in coarse sand is much higher than in fine sand, silica flour and Glass Ballotini. have little impact of sorptivity. High organic matter content dried unto the agricultural soil, is water repellent, but is overcome in solution of the root exudate compound; malonic acid has the greatest impact in relative wettability of soil with hydrophobic coating. The surface tension of xanthan at a concentration of 5 mg/ g-is greater that at 1 mg/g.