Topic outline

  • Summary

    Hydroponics is a new exciting educational tool to demonstrate plant growth to students. The term ‘hydroponic’ is used to describe plant cultivation in a water solution of soluble fertilizers or in an inert growing media. The creation of an educational hydroponic unit provides a visible insight to the process of plant growth to school pupils under real growing conditions. A closed-loop hydroponic unit will be created, which enables recycling of fertilizers and water, thereby minimizing environmental impacts and saving natural resources.  Thus, getting familiar with plant cultivation in a hydroponic situation is anticipated to motivate school pupils to become more conscious of the need to preserve the environment. Students are challenged by the prospect of growing plants without soil. Combining theoretical teaching with a paradigm of practical application makes it much more interesting for the pupils to participate.

     

  • Aims

    Students are becoming familiar with environment-friendly practices of plant cultivation and environmental factors involved in plant growth. The proposed case would provide insight to the full life cycle of plants through hands-on experience. The students will acquire the basic understanding on how plants are grown hydroponically and how input of natural resources in agriculture can be minimized through recycling. Thus, students will be educated to think more environment-friendly and search for more rational utilization of natural resources in the production process, including agricultural and food production.

  • Main activities

    Students will set up a closed-loop hydroponic unit in which plants will be growing in recirculating nutrient solution without the use of any solid medium for rooting. Thus, students will have the opportunity to monitor and document plant growth in a controlled environment. They will make observations, record data under different physiological plant stages, environmental conditions and study the impact of light, temperature, water, and nutrients on plant growth. Thus, students are anticipated to draw conclusions and make observations that will raise scientific questions and stimulate scientific discussions.

  • Involved actors

    teachers and researchers

  • Connection with the curriculum

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  • Where to find the application or case

    D. Savvas, H.C. Passam (Eds). Hydroponic Production of Vegetables and Ornamentals. Embryo Publications, Athens, Greece.

    http://www.embryopub.gr/index.php?target=products&product_id=23&sl=EN

    Savvas, D. 2012. Soilless Culture. Hydroponics – Substrates. Agrotypos Publishing, Athens, Greece (in Greek).

    http://www.agrotypos.gr/eshop/index.asp?mod=eshop_item&cID=87&pID=63565

     

  • Content

    Hydroponics is defined as “any method of growing plants without the use of soil as a rooting medium, in which all inorganic elements that are required for plant nutrition (except carbon which is fixed in the leaves through the process of photosynthesis) are supplied to the root system via the irrigation water”. The fertilizers used as sources of the nutrients to be supplied to the crop are dissolved to the irrigation water at proper concentrations and the resultant solution is termed “nutrient solution”. The proposed Best Practice is the establishment of a closed-cycle hydroponic cultivation system, in which the nutrient solution will be constantly recirculating. The cultivation of plants in closed hydroponic systems can substantially reduce the pollution of water resources by nitrates and phosphates originating from fertilizer residues, while contributing to an appreciable reduction in water and fertilizer consumption.

    The hydroponic school garden proposed as one of the Best Practices will be a simple closed-loop hydroponic unit, consisted of:

    1. A trough continuously supplied with flowing nutrient solution that will be used to accommodate the plant roots,
    2. A supply tank that will serve both as a reservoir of nutrient solution to be supplied to the plants and as catchment tank of the returning solution to be reused,
    3. A replenishment tank that will be used to automatically replenish the consumed nutrient solution in the supply tank via a floating valve,
    4. A small pump that will be used to supply nutrient solution to the plants
    5. Irrigation pipes to supply nutrient solution to the upper edge of the trough and collect the remainder solution after flowing through the plant roots at the lower edge of the trough.

    The supply of nutrient solution to the plants and its recirculation within the hydroponic unit will be continuous. No water or nutrients will be discharged. Standard water-soluble fertilizers will be used to prepare concentrated stock solutions which will be diluted at a ratio of 1:100 to prepare the final nutrient solution whenever needed. The latter will be regularly added to the replenishment solution tank (e.g. every two or three days) to compensate for nutrient and water uptake by plants. No other operations are needed for fertilization and irrigation of the plants, since both nutrients and water will be automatically provided through the recirculating nutrient solution.

  • Relation to a green topic and curriculum

    With a hydroponic school garden, students will have the opportunity to learn about the food chain, the cost and effort of producing their own vegetables. Furthermore, since the hydroponic school garden will be a closed system in which nutrients and water residues will be collected and recycled, students will be educated to save the natural resources through recycling technologies. 

  • Being interdisciplinary: Drawing upon many academic disciplines and teaching methods

    Hydroponics can be an important educational tool especially because of its flexibility and its approach to a plethora of subjects. Participating in the construction of the hydroponic unit students will design technology, identifying problems, proposing and implementing solutions. On the other hand, with the maintenance of this unit they will try to understand science.    

  • Relevance to the daily life of students

    Children have a natural affinity of growing living organisms. With a hydroponic garden they will understand the basic growth needs of plants, and learn through a practical paradigm that plants need only inorganic nutrients, water and oxygen for their growth, unlike animals that need organic substances such as proteins, lipids, carbohydrates, vitamins, etc. Furthermore, students will be educated through practice what chemical elements are essential nutrient for plants, at what amounts and what happens if an essential nutrient is deficient or fully omitted in the supplied nutrient solution.    

  • Based on accurate and factual professional expertise

    Control of soil-borne pathogens is very difficult in greenhouse crops where crop rotation is not feasible. Traditionally, this problem was encountered using methyl bromide (MB) once per year for soil sterilization. However, according to the Montreal Protocol, MB cannot be used any more for soil fumigation because it destroys the ozone layer in the stratosphere. To avoid the need for soil fumigation, most growers switched to hydroponics, which enables a more efficient utilization of fertilizers and water through recycling of the nutrient solution