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Hypochlorite Application for Controlling Algae Biofilm Formation, Microorganisms and Tomato Production in Recirculating Systems

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Physical and chemical disinfection methods are used or are under investigation in greenhouse facilities to minimize the occurrence of pathogens and the application of pesticides in recirculating systems. Since the most of these methods differ in their effectiveness, more investigation is needed to produce healthy plants in a sustainable way. Therefore, the present study is focused on the identification of interactions between hypochlorite (ClO−) used as a disinfectant for a recirculating system and algae formation, spread of microorganisms, as well as plant development. As such, on-site produced potassium hypochlorite (1 % KClO) solution were supplemented using proportional injection control once a week for 90 min, as a disinfectant, into a recirculating tomato production system (NFT) until a free chlorine concentration of 1 mg L−1 (D I) and 2 mg L−1 (D II) were reached, respectively. The formation of the algae biofilm was reduced by 15 % (D I) and 48 % (D II). These treatments also suppressed cultivated microorganisms up to 100 %. Tomato plants exposed to the treatment D I showed a comparable plant height to the control plants after 7 weeks, whereas D II led to a significant increase in plant height of 12 cm. However, the formation of leaves was more pronounced by treatment D I. After a growing period of 7 weeks, a significant difference in leaf number up to 2.9 leaves per plant was calculated compared to the other treatments. The same treatment had the largest positively impact on the fruit yield and number of fruit, which were increased by 10 and 15 %, respectively, compared to the control plants. Under consideration of all results, the most promising effects of ClO− as a disinfectant for hydroponic systems were achieved with a free chlorine concentration of 1 mg L−1 (D I), where phytotoxic effects can be excluded. http://link.springer.com/article/10.1007%2Fs10343-015-0351-3
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ORIGINAL ARTICLE
Eingegangen: 3. September 2015 / Angenommen: 21. September 2015
© Springer-Verlag Berlin Heidelberg 2015
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DOI 10.1007/s10343-015-0351-3
plants exposed to the treatment D I showed a comparable
plant height to the control plants after 7 weeks, whereas
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However, the formation of leaves was more pronounced
by treatment D I. After a growing period of 7 weeks, a
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plant was calculated compared to the other treatments. The
same treatment had the largest positively impact on the
fruit yield and number of fruit, which were increased by
10 and 15 %, respectively, compared to the control plants.
Under consideration of all results, the most promi-
sing effects of ClO as a disinfectant for hydroponic sys-
tems were achieved with a free chlorine concentration of
1 mg L1 (D I), where phytotoxic effects can be excluded.
.H\ZRUGV Potassium hypochlorite · Disinfectant ·
Hydroponic systems · Algae · Microorganisms · Plant
development · Tomato yield .
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$EVWUDFW Physical and chemical disinfection methods are
used or are under investigation in greenhouse facilities to
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of pesticides in recirculating systems. Since the most of
these methods differ in their effectiveness, more investiga-
tion is needed to produce healthy plants in a sustainable
way. Therefore, the present study is focused on the identi-
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as a disinfectant for a recirculating system and algae for-
mation, spread of microorganisms, as well as plant devel-
opment. As such, on-site produced potassium hypochlorite
(1 % KClO) solution were supplemented using proportional
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into a recirculating tomato production system (NFT) until a
free chlorine concentration of 1 mg L1 (D I) and 2 mg L1
(D II) were reached, respectively.
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15 % (D I) and 48 % (D II). These treatments also sup-
pressed cultivated microorganisms up to 100 %. Tomato
D. Dannehl () · I. Schuch · U. Schmidt
Faculty of Life Sciences, Albrecht Daniel Thaer – Institute of
Agricultural and Horticultural Sciences, Division Biosystems
(QJLQHHULQJ+XPEROGW8QLYHUVLWlW]X%HUOLQ
Albrecht-Thaer-Weg 3,
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e-mail: Dennis.Dannehl@agrar.hu-berlin.de
Y. G ao
newtec Umwelttechnik GmbH,
Am Borsigturm 62,
13507 Berlin, Germany
S. Cordiner
The New Zealand Institute for Plant and Food Research Ltd.,
Private Bag 11600,
Palmerston North 4442, New Zealand
1 3
... Hypochlorite (CLO-) used for preharvest processes can eliminate organic substances and kill pathogens (Cayanan et al., 2009). Studies also show its utility to control algae biofilm formation in greenhouses (Dannehl et al., 2015). Nevertheless, a drawback of this disinfection method is possible initiation of unwanted chlorate in fruits such as tomatoes (Dannehl et al., 2016). ...
... The dry weight of the algae on the fleece in the disinfection row is 0.166 g in comparison to the one on the fleece from the control row with 0.363 g. This is similar to results of Dannehl et al. (2015) and Yiasoumi (2005) that also show an increasing efficacy against algae biofilm formation with increasing dosages of potassium hypochlorite in irrigation water. Xin et al. (2010) showed that algae growth requires nutrients like phosphorous and nitrogen. ...
... Xin et al. (2010) showed that algae growth requires nutrients like phosphorous and nitrogen. Stemming algae formation with hypochlorite can therefore attend more nutrients of irrigation water being available for plants and such fertilizers can be reduced (Dannehl et al., 2015). Algae biofilm is also a platform for pathogens. ...
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Tested in experimental scale, an innovative system for electrolytic water disinfection in greenhouses (SeWiG) was very efficient. It was developed by Humboldt-Universität zu Berlin and newtec Umwelttechnik GmbH. With scaling up this system for industrial greenhouses, the new technology will be tested, validated and optimized under practical conditions. The implemented technology will be incrementally scaled-up. After successful installation of the disinfection system within a separated part of an industrial greenhouse, two large-scaled greenhouses will use the on-site produced hypochlorite as a disinfectant for irrigation or drain water applied for vegetables and ornamental plants. The effects on plant growth, yield and product quality will be controlled and particular attention is paid to chlorate and perchlorate. Due to the first results, both pesticides are under the limits given by the European Commission. This can be related to the short dwell time of the disinfectant before dosing based on the on-demand production of fresh hypochlorite. Hypochlorite is dosed by the method of shock disinfection, which might decrease the accumulation of unwanted ingredients in plants. The special feature of the new system for electrolytic water disinfection is the functional superiority over common methods such as filtration, ultraviolet irradiation, heating, ozonation or chlorine dioxide. Worth highlighting is its high effectiveness against plant viruses and the reduced risk for users, plants and the environment while less energy is needed, compared to other disinfection systems. Besides a reduced formation of algae biofilm, a reduced application of fertilizers is expected. All parameters mentioned before will be monitored within this study.
... In the corresponding study (Dannehl et al. 2015a), tomato plants were continuously irrigated within a closed circuit on plastic channels (NFT) with a disinfectant solution produced on site and dosed discontinuously over a period of three months (1/week for 90 min) in concentrations of 1 mg (variant DI) or 2 mg free chlorine/l (variant DII) in fertiliser-containing irrigation water (contents including ammonia). In the result, no yield reduction was determined while antimicrobial efficacy was found to be improved (Dannehl et al. 2015B). However, the chloride content in water rose following discontinuous introduction of disinfectant by 14 mg/l (DI) on average, or 21 mg/l (DII) (Dannehl et al. 2015a), whereby the crop growing recommendation for hydroponic tomatoes of < 532 mg chloride/l (SOnneVelD and StraVer 1988) was undersupplied, even after three months without water change. ...
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