Oxygenated Nutrient Solution of Organic Greenhouse Tomato: Soil Biological Activity,
Root Disease Tolerance, Plant Growth and Yield
Carline Jean-Paul1, Valérie Gravel1,2, Nicolas Gruyer1, Claudine Ménard2, Philippe Rochette3,
Steeve Pepin1,4, Hani Antoun1,4 and Martine Dorais1,2
1
Horticultural Research Centre, 2Agriculture and Agri-Food Canada, Envirotron bldg, Laval
University, QC, Canada, G1V 0A6, Doraisma@agr.gc.ca; 3Agriculture and Agri-Food Canada,
Soils and Crops Research and Development Centre, Ste-Foy, QC, Canada, G1V 2J3; 4Département
des sols et de génie agroalimentaire, Laval University, QC, Canada, G1V 0A6
Super saturation of the nutrient solution with O2 can have a beneficial effect on vegetable yield.
However, little is known about the effect of O2 enrichment of the nutrient solution for organic
greenhouse crops and on the biological activity of the growing medium. The objective of this
study was to investigate the effect of O2 enrichment of the nutrient solution combined with
beneficial microorganisms on soil activity, plant growth and development, yield, fruit quality and
root disease tolerance. Seedlings of Lycopersicon esculentum cv. Trust were transplanted to 14-L
containers filled with a sandy loam amended with 10% bovine organic compost, and grown in a
greenhouse from May to October 2007. Soil-surface CO2 flux and gas concentrations (O2, CO2,
NOx, CH4) in the soil were measured every two weeks to determine soil biological activity. The
organic nutrient solution (suspension of pelleted hen manure) was enriched or not (ambient O2,
control) with pure O2 (25 ppm) in the nutrient tea reservoir. Plants were inoculated twice with a
suspension of 1) Cocktail of growth promoters, 2) Trichoderma harzianum, 3) Ascophyllum
nodosum, 4) Mixture of Pseudomonas putida and T. atroviride, 5) Plant control (water), and 6)
Soil control (water). Four weeks before the end of the experiment, plants were inoculated with a
suspension of Pythium ultimum, and their root infection evaluated. Results showed that
oxygenation had a positive effect on tomato yield of class #1 fruits. However, there were no
effects of O2 and growth promoter treatments on growth parameters. Since low O2 levels (4-6
ppm) were observed at the dripper compared to the bottom of the nutrient tea reservoir (25-27
ppm), the observed effect of O2 may be related to higher microorganism population in the
organic nutrient solution instead of a direct O2 effect at the root level. No significant effect of
oxygenation and plant growth promoters on Pythium infestation was observed suggesting that
organic soils already have microorganisms able to protect plant roots from root disease such as
Pythium. Results will also be discussed in term of soil activity, mineralization rate, nutrient
uptake and fruit quality.