Articles
Disinfection of used sawdust and its effect on yield of hydroponically grown tomatoes
Article number
1410_4
Pages
23 – 30
Language
English
Abstract
Sawdust is readily available in South Africa, making it more affordable to growers than imported substrates.
In addition, sawdust has favourable physical properties for plant growth, such as high porosity, while maintaining a good water retention capacity.
Emerging hydroponic farmers find it challenging to obtain new sawdust every season due to limited affordability; as a result, there is a need to explore the potential of reusing it.
With this intention, four disinfection methods were evaluated in terms of their restriction to pathogen infestation and yield of tomatoes grown in an open-bag hydroponic system, operating under a non-temperature-controlled plastic tunnel: 1) solarization; 2) soaking in water; 3) soaking in sporekill (containing 120 g of Didecyldimethylammonium chloride as active ingredient per L) applied at a rate of 1 L 1000 L-1 of substrate dissolved in water, and 4) soaking in 50% hydrogen peroxide (1 L 1000 L-1 of substrate dissolved in water) for 24 hours, followed by sun-drying for two weeks before their reuse to grow tomatoes hydroponically.
The microbial analysis of the disinfected sawdust showed that the colony-forming units (cfu) of bacteria decreased with treatments sun-drying (4.1×1011 cfu g-1), water (7.0×1011 cfu g-1) and sporekill (1.3×1012 cfu g-1), while hydrogen peroxide increased detectable levels to 4.6×1013 cfu g-1, compared to before treatment (4.4×1012 cfu g-1). In contrast, the fungal colonies were reduced the most by hydrogen peroxide (2.0×105 cfu g-1), followed by sporekill (3.5×105 cfu g-1) and water (3.7×105 cfu g-1), while increased with sun-drying (7.3×105 cfu g-1), compared to before treatment (4.3×105 cfu g-1). The resultant marketable yield was significantly higher under the solarization method (3.91 kg plant-1), followed by soaking in sporekill (3.4 kg plant-1) and water (3.29 kg plant-1), while the lowest yield was observed with the hydrogen peroxide disinfection method (2.68 kg plant-1) which was not significantly different from the new sawdust (2.86 kg plant-1). These findings demonstrate that disinfected old sawdust can potentially be reused in hydroponics, as no major disease incidence was observed.
This can contribute to reduced input costs and increased profitability for hydroponic farmers.
In addition, sawdust has favourable physical properties for plant growth, such as high porosity, while maintaining a good water retention capacity.
Emerging hydroponic farmers find it challenging to obtain new sawdust every season due to limited affordability; as a result, there is a need to explore the potential of reusing it.
With this intention, four disinfection methods were evaluated in terms of their restriction to pathogen infestation and yield of tomatoes grown in an open-bag hydroponic system, operating under a non-temperature-controlled plastic tunnel: 1) solarization; 2) soaking in water; 3) soaking in sporekill (containing 120 g of Didecyldimethylammonium chloride as active ingredient per L) applied at a rate of 1 L 1000 L-1 of substrate dissolved in water, and 4) soaking in 50% hydrogen peroxide (1 L 1000 L-1 of substrate dissolved in water) for 24 hours, followed by sun-drying for two weeks before their reuse to grow tomatoes hydroponically.
The microbial analysis of the disinfected sawdust showed that the colony-forming units (cfu) of bacteria decreased with treatments sun-drying (4.1×1011 cfu g-1), water (7.0×1011 cfu g-1) and sporekill (1.3×1012 cfu g-1), while hydrogen peroxide increased detectable levels to 4.6×1013 cfu g-1, compared to before treatment (4.4×1012 cfu g-1). In contrast, the fungal colonies were reduced the most by hydrogen peroxide (2.0×105 cfu g-1), followed by sporekill (3.5×105 cfu g-1) and water (3.7×105 cfu g-1), while increased with sun-drying (7.3×105 cfu g-1), compared to before treatment (4.3×105 cfu g-1). The resultant marketable yield was significantly higher under the solarization method (3.91 kg plant-1), followed by soaking in sporekill (3.4 kg plant-1) and water (3.29 kg plant-1), while the lowest yield was observed with the hydrogen peroxide disinfection method (2.68 kg plant-1) which was not significantly different from the new sawdust (2.86 kg plant-1). These findings demonstrate that disinfected old sawdust can potentially be reused in hydroponics, as no major disease incidence was observed.
This can contribute to reduced input costs and increased profitability for hydroponic farmers.
Authors
N.A. Araya, R.I.S. Mahlangu, H.T. Araya, R. Sutherland, M. Truter, C.P. du Plooy
Keywords
organic growth media, non-temperature-controlled plastic tunnel, sun-drying, hydrogen peroxide
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