The Effects of Ozonated Irrigation Water on Soil Physical and Chemical Properties (OVERVIEW)

Logan Raub, Christopher Amrhein, and Mark Matsumoto

University of California, Riverside

Received for Review: 6 July 1999

Accepted for Publication: 10 March 2000

Study Synopsis

The study sought to prove claims that ozone in irrigation water can improve crop vigor, reduce insect and disease, enhance water penetration, and reduce fertilizer needs. The study concluded that ozone did produce some benefits, including an increase in hydraulic conductivity and decreased clay dispersion in loamy soil.  Every soil sample tested also exhibited lower pHs and higher electrolyte concentrations after ozonation.

Positive Findings from the Study

• “In every soil tested, the drainage water from the ozone-treated columns had lower pHs and higher electrolyte concentrations. This is attributed to organic matter oxidation and the weak acid properties of ozone.” Note: This quote from the following study is a reoccurring them in ozone studies. The higher electrolyte concentration and reduction in organic matter are two things that directly increase water percolation.

• “Pedersen and Redsun (1996) interviewed farmers that had used ozone in their irrigation water and there was general agreement that the topsoil in ozone treated fields was more porous and spongy. These farmers also reported less standing water, decreased clodding, and deeper water penetration into the soils. All of these observations are in agreement with the effects one would predict from an amendment that increases clay flocculation.” Note: The Pedersen/Redsun study was farmers’ reports following a longer period of ozonation. The farmers’ observations are consistent with other ozone-users’ results and other case study results.

• “We found that ozone increased the saturated hydraulic conductivity and decreased clay dispersion.” NOTE: Both an increased hydraulic conductivity and decreased clay dispersion mean an increase in percolation.

• “It has been found that the ozone helps remove clay turbidity through coagulation” and “Ozone has an important effect on coagulation, flocculation, and filter performance.” NOTE: All of these effects mean increased percolation.

• “The ozone treated columns had significantly less clay in the leachate, suggesting that clay flocculation was improved as a result of ozonation.” NOTE: Improvement in clay flocculation results in increased percolation.

• “The improvement in physical properties that was observed could be attributed to higher electrolyte concentrations in the soil water and lower pH values, both of which lead to improved clay flocculation and reduced dispersion.” NOTE: Again, the effect of this is increased percolation.

Negative Findings from the Study

Please be aware that, for most of the inconclusive or negative findings in the study, the article attributes this to the conditions of the study itself lacking.  The study was short-term, and did not use a large enough volume of ozone gas to optimize the effect on the soil.

• “Contrary to previous reports, there was no significant difference in the tensile strength test between any of the ozone-treated and untreated columns.” NOTE: As the article also clearly states, “The tensile strength test is not very sensitive to small changes in soil structure. Additionally, it may take several months of leaching, drying, and cultivating before significant changes to the strength of the soil would be measured by this test.”  This study took place only over a few days.

• “In the Millham and Ramona soils, there were no clear trends and largely no significant differences in the water holding capacity due to ozonation.” Note: Ozonation does not increase soil holding capacities, it increases its ability to percolate water through.

• “The ozone was rapidly lost once the water entered the soil columns, and we were unable to detect ozone in the leachate, even from very thin soil columns. We speculate that the higher concentrations of ozone were needed for ozone to move into the soil.” NOTE: The amount of ozone used in this study was less than the recommended level to increase soil percolation.

• “Destruction of this organic matter in the surface layer by ozonation might lead to long-term problems with infiltration and crusting.” NOTE: This statement is speculative about what might happen in the long term, based on this short-term study. Long-term reports indicate that these effects do not occur with the prolonged use of ozonation.

Thoughts and Comments

This study, like many other ozone, oxygen, or CO₂ studies involving soil, was done without the expertise of a Water Chemist and Physical Chemist to approve procedure and interpret results. Nonetheless, it is a positive step forward in demonstrating ozone’s effect on soil.