APPLICATION OF DILUTED CHLORINE DIOXIDE TO RADISH AND LETTUCE NURSERIES INSIGNIFICANTLY REDUCED PLANT DEVELOPMENT

The possible toxicity of a commercial chlorine dioxide preparation (Ha lox E-100) was evaluated on radish and lettuce seedlings growing in po ts under controlled conditions. A single application of various diluti ons to radish seedlings growing in a sterile or nonsterile commercial plant substrate only slightly decreased plant dry weight. At the end o f the experiments, the plants appeared unaffected by the treatments. O ther common plant parameters (root and stem length, number of true lea ves) were unaffected or even enhanced. Halox did not reduce the total level of soil bacteria even after four consecutive applications at any dilution rate. In nonsterile soil, high Halox dilution (1:1000) signi ficantly decreased plant dry weight, and the other concentrations (1:1 0,000; 1:50,000, and 1:100,000) had no apparent effect on the size of the plants. In sterile soil, high concentrations of Halox (1:1000 and 1:10,000) significantly decreased plant growth, but higher dilutions p roduced no significant reduction in plant dry weight. For radish plant s growing in organic matter-free sand only, dilution of 1:10,000 reduc ed plant growth. On lettuce plants, dilutions from 1:5000 to 1:25,000 did not reduce plant growth. High levels of Halox (1:1000) were toxic to both radish and lettuce seedlings growing in sand and resulted in c hlorosis and significant depression of plant growth. Further dilutions of Halox (equivalent to the level used in water disinfection) signifi cantly decreased toxicity for both plant species. Low concentrations o f Halox (>1:50,000) had no apparent effect on the appearance of both p lant species. In conclusion, this study suggests that chlorine dioxide -treated drinking water can be considered safe for growing plants; thi s treatment should be further evaluated using other plant species unde r more realistic growth conditions. (C) 1996 Academic Press, Inc.