The effects of ozonated irrigation water on soil physical and chemical properties

There are reports that ozone in irrigation water can improve crop vigor, reduce insect and disease, enhance water penetration, and reduce fertilizer needs. It has been noted that ozone treated field soils seem spongier and have less standing water. Here we report on a laboratory column study on the effects of ozonated irrigation water on hydraulic conductivity, soil hardness (aggregate strength), clay dispersion, soil swelling, and changes to the chemical composition of the leachate water. Additional batch studies were conducted to characterize the factors affecting the rate of ozone loss in soil/water suspensions and the results used in a mathematical model to predict ozone movement into a soil. We found that ozone increased the saturated hydraulic conductivity and decreased clay dispersion in a loamy soil, but not if the soil had an exchangeable sodium percentage >15%. In two other soils tested, the ozone effects were mixed or insignificant. In every soil tested, the drainage water from the ozone-treated columns had lower pH's and higher electrolyte concentrations. This is attributed to organic matter oxidation and the weak acid properties of ozone. The rate of ozone degradation in soil water could be modeled using the total organic carbon content of the soil, the pH, and the soil/water ratio. Based on the rate of ozone loss in soil/water suspensions, the calculated depth of ozone penetration during the initial wetting of the soil was <2 mm, indicating that the reaction may be limited to the surface.