Abstract
The aim was to determine the suitability of various substrates for application in a closed system of soilless tomato cultivation, based on the potential fitness of drainage waters from these substrates for recirculation. Four substrates were used: rockwool, coir substrate, lignite substrate (Carbomat) and biodegradable organic substrate (Biopot). Tomato plants grown in these substrates were fertilized with the same amount of nutrient solution, containing the same concentration of nutrients. The characteristics of drainage water from these substrates were analyzed during cultivation. The highest amount of drainage water was collected from the lignite substrate Carbomat. However, these leachates showed good properties for further recirculation: low electro conductivity and turbidity, high nutrient content, moderate microbial load with high population of Trichoderma fungi, and being beneficial for plant growth. Moreover, Carbomat produced the highest tomato yield compared to other substrates. This indicates that this organic substrate is an efficient alternative to rockwool and its drainage water may be reused in a recirculation system. On the contrary, the drainage water from the Biopot substrate showed the worst qualities: high pH and low EC, low concentration of nitrate nitrogen and phosphorus, very high turbidity and a high number of microorganisms. These parameters do not qualify Biopot drainage waters for reuse.
Highlights
Soilless culture is a worldwide-used technique of plant production
For a closed system of soilless growing, the quality of the drainage waters leaking from cultivation mats is a key factor, determining the possibility of their reuse in nutrient solution circulation systems
Substrates that have shown good effects in open system tomato cultivation may not be favorable in a closed system due to the low suitability of draining waters for recirculation
Summary
Soilless culture is a worldwide-used technique of plant production. The other advantage of such cultivation systems is the independence from soil quality and environmental conditions. In some countries (the Netherlands, Spain, US, Canada) soilless culture is one of the most popular techniques in vegetable production [2,3]. It was found that this system has some negative impacts on the environment: the used growing substrate slabs’ disposal and an excessive nutrient solution leaking from cultivation mats. The most-used growing medium is mineral wool slabs [4]. This material has many advantages, such as substrate uniformity, low weight and ease of handling, and efficiency in plant production
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