In seedlings it is important to verify that ozone does not cause damage, because plants are more sensitive to ozone in juvenile stages (Timonen et al., 2004).
Ozone, applied diluted in water and sprinkled on seedlings of ornamental perennial species such as Salix integra, Hydrangea paniculata or Spiraea japonica, has proven to be a very effective treatment against fungal foliar diseases, ultimately causing a saving of chemical products. This fact in a world that increasingly requires more ecological treatments, and in which the demands for reducing the residues of fungicides and other pesticides are increased not only in fruits but also in foods processed with them (Edder et al., 2009 ).
Ozone is considered as a possible organic biocide because apart from not leaving chemical residues, it acts in two ways, a direct and an indirect way through the ROS species (Zotti et al., 2008). Toxic doses in sprinkler irrigation were observed from 1.5 ppm on the mentioned perennial seedlings, in applications of 7.5 minutes of irrigation / day (approx 1L per plant / day) for 6 weeks. The non-toxic dose was observed in concentrations below 1.5 ppm, such as 0.5 ppm. At these levels, an elimination of algae and biofilm is ensured, without showing phytotoxic effects (Graham et al., 2009).
In hydroponic or semi-hydroponic systems, water (30%) and fertilizer (40%) were saved by recycling leached or closed-circuit water (Runia, 1988, 1993, 1994; McDonald, 2007).
In hydroponic tomato cultivation with nutritive solution + ozone, larger tomato plants were obtained than in nutritive solution - ozone. It was demonstrated in this work that the concentration of macro and micronutrients of the nutrient solution is not modified: there is no variation in the levels of Calcium, Potassium, Magnesium, Phosphate, Ammonium, Nitrate, Copper, Molybdenum or Zinc depending on the dose increasing ozone up to 10 ppm. There is a drastic decrease in Manganese (from 0.5 ppm) and Iron (from 5 ppm). To avoid that, Terazoe (2001) proposed the ozonation of the water in a separate tank before adding the nutrients or separating the irrigation with ozone and the irrigation of nutrients. Despite this drastic decrease in the irrigation solution, there are no differences in the content of these nutrients in the leaves, which is not negatively affecting their normal development. There is a notable decrease in the incidence of root rot, typical of hydroponic cultivation (Ohashi-Kaneko et al., 2009).
Questions:
So, everything seems quite good in that way, but many questions comes to my mind:
1) Given the potential of this tool, why is ozone not an essential tool in agriculture today?
2) Are we still in a time of transition to tools such as ozone in agriculture? Or, on the other hand, do people distrust this technology due to unethical actions carried out by certain companies in the manufacturing sector of ozone generators and other innovative technologies?
3) Are there few studies in agriculture with ozone application? Or perhaps the studies show very contradictory results among them?
Feel free to discuss and propose your own questions/answers,
Thank you!
JD
References:
Edder, P., Ortelli, D., Viret, O., Cognard, E., Montmollin, A. D., & Zali, O. (2009). Control strategies against grey mould (Botrytis cinerea Pers.: Fr) and corresponding fungicide residues in grapes and wines. Food Additives and Contaminants, 26(5), 719-725.
Graham, T., Zhang, P., Zheng, Y., & Dixon, M. A. (2009). Phytotoxicity of aqueous ozone on five container-grown nursery species. HortScience, 44(3), 774-780.
Ohashi-Kaneko, K., Yoshii, M., Isobe, T., Park, J. S., Kurata, K., & Fujiwara, K. (2009). Nutrient solution prepared with ozonated water does not damage early growth of hydroponically grown tomatoes. Ozone: Science & Engineering, 31(1), 21-27.
Timonen, U., Huttunen, S., & Manninen, S. (2004). Ozone sensitivity of wild field layer plant species of northern Europe. A review. Plant Ecology, 172(1), 27-39.
Zotti, M., Porro, R., Vizzini, A., & Mariotti, M. G. (2008). Inactivation of Aspergillus spp. by ozone treatment. Ozone: Science and Engineering, 30(6), 423-430.
It is a very interesting topic. I would agree that this technique seems to be promising in the near future. however, the capital cost of exposing ozone in many stages of germination and cultivation process still needs to be counted.
for the technical part, the acute exposure seems to be more preferred since it does not need any specific requirements to trap the ozone or constantly pump the gas into the system or specifically to the water. Nevertheless, the acute exposure still has many drawbacks such as less effectiveness on pathogen removal (proven in waster treatment system).
Were your experiments done with ozone generated from air or from oxygen? If from air, you may find other molecules formed in the generator, are interfering with your results.
In answer to question 1, I would guess that it is the same as why ozone is not more used in Medicine i.e. there have been lo large scale trials. The reason for the lack is the same. There is no way of protecting your investment in a trial nor large money to be made.
It certainly is a cheap biocide. Even the equipment needed is cheap.
I have had saline ozone IVs and my condition did improve although it's back to where it was prior to treatment 2yrs ago.
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