ISHS Acta Horticulturae 648: South Pacific Soilless Culture Conference - SPSCC
MENNO-FLORADES (9 % BENZOIC ACID) AS AN ADDITIVE TO THE NUTRIENT SOLUTION OF A HYDROPONICALLY GROWN TOMATO CROP |
| Authors: | W. Wohanka, S. Lindemann |
| Keywords: | soilless culture, tomato, disinfectant, benzoic acid, fluorescent pseudomonads |
| Abstract:
The objective of this study was to identify effects of the commercial disinfectant MENNO-Florades (a.i.: 9 % benzoic acid) on the microflora of nutrient solutions from hydroponic growing systems in vitro and on the yield of a hydroponically grown tomato crop. For the in vitro experiments, different amounts (100 to 800 ppm) of MENNO-Florades were added to samples of nutrient solutions from a hydroponically grown gerbera crop. The samples were incubated at 20 °C with continuous aeration for five days. Within two days after application of the disinfectant, a marked increase of the number of fluorescent pseudomonads occurred. This was followed by a decrease of this bacterial group with the lower (100 and 200 ppm) but not with the higher concentrations (400 and 800 ppm). Based on the in vitro experiments, nutrient solutions of a tomato crop (cv. Espero) were treated with MENNO-Florades. The disinfectant was applied in different ways: i. addition with every replenishment of the nutrient solution, ii. once a week with 100 ppm when filled to the maximum level of water storage and iii. every third week with 300 ppm when filled to the maximum level of water storage. The suspected multiplying effect of MENNO-Florades on the fluorescent pseudomonads in nutrient solutions could be confirmed. However, this was accompanied by a short term, drastic decrease of the oxygen content in the storage tanks. The tomato plants were decapitated after the development of the 4th truss and the crop was terminated 16 weeks after planting. No phytotoxic effects on roots or shoots could be detected. The yield of the plants with three-weekly applications of MENNO-Florades was significantly higher (12.6 %) than that of the control. | |
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