Soilless cultivation

Aims

•  To introduce the techniques of growing plants without soil and to the relevant terminology •  To outline the field of application of soilless cultivation systems in commercial greenhouse production and explain their advantages and disadvantages with special emphasis on the environmental impacts. •  To provide a sufficient background on: a) the physical and chemical properties of horticultural substrates and b) the specific characteristics of the most important of them. •  To provide the necessary knowledge on the chemistry of nutrient solutions to the students and to enable them to calculate nutrient solutions of any desirable composition. •  To provide sufficient knowledge background on the management of plant nutrition and irrigation in commercial soilless cultivated crops. •  To provide advanced knowledge on modern methods of nutrient and water recycling in closed-cycle soilless cultivation systems  

Prerequisites

•  Basics of inorganic chemistry •  Principles of plant nutrition and crop physiology
 
  

Learning Outcomes

After completing the unit, attendees will be able to: •  assess the possibilities of applying soilless culture in a commercial greenhouse and estimate the expected benefits •  select the most appropriate soilless cultivation system and growth medium in each specific situation •  calculate nutrient solutions for any crop species, cultivation system, and irrigation water source •  manage plant nutrition and irrigation in soilless cultivations •  contribute to the study and implementation of open or closed-cycle soilless culture projects •  disseminate knowledge on soilless culture  

Syllabus

Hydroponic systems: Systems involving solely water as a substrate (deep water culture, floating hydroponics, NFT, plant plane hydroponics, aeroponics). Systems involving an aggregate as a substrate (bag culture, container culture, trough culture, thin layer systems, various alternative systems). Equipments in hydroponics: Installations used to prepare and deliver nutrient solution, sensors, equipment for the lay-out of the crop, equipment for irrigation and nutrient solution recycling. Substrates: Physical properties of substrates (bulk density, particle size distribution, porosity, water release curves, hydraulic conductivity, impact of physical properties on irrigation management in hydroponics). Chemical properties of substrates (pH, ion sorption, ion exchange). Substrate analysis (determination of water soluble and exchangeable nutrients, CEC, AEC, organic matter content, pH, EC). Description of substrates (sand, gravel, rockwool, expanded minerals, pumice, zeolite, pyroclastic materials, peat, coir, tree bark, sawdust, wood fibres). Composition of nutrient solution: Calculation of nutrient solutions for open systems. Calculation of nutrient solutions for closed systems: concept of drainage solution plus fresh water, concept of uptake concentrations or uptake ratios. Nutrient management in hydroponics: Effects of pH, EC and nutrient ratios on plant growth, yield and quality. Management of nutrient solution in open systems. Monitoring and adjusting the nutrient supply. Introduction to nutrient solution recycling. Methods of nutrient solution recycling. Disinfection in closed hydroponic systems: Nutrient solution disinfection (heating, UV-irradiation, chemical treatments by means of ozone, hydrogen peroxide, chlorine, iodine, etc., membrane filtration, slow sand filtration).. Irrigation control in hydroponics: Characteristics of irrigation systems (capacity, uniformity). Delivery Systems (overhead systems, drip irrigation, subirrigation). Irrigation scheduling (preset schedule, sensor-based schedule, transpiration-based schedule).  

Content Delivery

After an introduction to the scientific bases of soilless culture and a presentation of the principal terminology, all soilless culture systems are presented in detail. The presentation of each system is based not only on an oral description but also on many photos and drawings serving to outline in detail both the functional and the construction characteristics of them. A second cycle of lectures is devoted to the substrates used in soilless culture and their characteristics. After a presentation of the physical characteristics of the substrates, the students are taught how to evaluate a porous medium based on its moisture characteristic or water retention curve (WRC). Students receive WRC of known substrates as case studies and each of them is asked to evaluate a substrate by computing characteristics such as container capacity, air filled porosity, easily available water, water buffering capacity and relative unsaturated hydraulic conductivity, and commenting the results. Other important topics for soilless culture included in this unit are the composition and supply of nutrient solution and the management of crop nutrition and irrigation. Following presentation of basic knowledge, students are trained to use a standard method which enables calculation of the amounts of fertilizers needed to prepare a nutrient solution of a given composition. A specific computer programme, which is available at the web site of the Agricultural University of Athens, is used for this purpose and the students are trained to use this software application. Furthermore, students are taught how to select the appropriate nutrient solution composition for a given horticultural crop, how to modify this depending on climatic parameters, growth stage and season of the year and how to manage fertigation in open and closed hydroponic systems. In addition to the presentation of the methodology and the data, the students receive case studies to work on.  

Coursework And Assignment Details

Evaluation of students will be based on a written examination. The questions and assignments to be carried out in the examination are listed below. -                      Students will be asked to answer to two questions regarding the scientific basis and the technical layout of soilless cultivation systems, their advantages and their disadvantages. Each question will be evaluated with a maximum of 10 points (grading scale 0 – 10). The primary sources of knowledge needed to answer to these questions are Chapters 3 (Equipment for Hydroponic Installations) and 4 (Hydroponic Systems) of the book “Hydroponic Production of Vegetables and Ornamental Plants”, edited by Savvas, D. and H.C. Passam, 2002. -                      Students will be asked to answer to a question regarding the physical or chemical characteristics of substrates. The question will be evaluated with a maximum of 10 points (grading scale 0 – 10). The primary source of knowledge needed to answer to this question is Chapter 2 (Substrates and Their Analysis) of the book “Hydroponic Production of Vegetables and Ornamental Plants”, edited by Savvas, D. and H. Passam, 2002. -                      Each student will be asked to quantify relevant physical characteristics and provide a general assessment of a certain substrate based on a given water retention curve. This assignment will be evaluated with a maximum of 10 points (grading scale 0 – 10). The primary source of knowledge needed to answer to this question is Chapter 2 (Substrates and Their Analysis) of the book “Hydroponic Production of Vegetables and Ornamental Plants”,edited by Savvas, D. and H.C. Passam, 2002. -                      Students will be asked to calculate the weights of fertilizers needed to prepare a nutrient solution of a given target composition. All formulae needed for the calculations will be given to the students. This assignment will be evaluated with a maximum of 20 points (grading scale 0 – 20). The primary source of knowledge needed to answer to this question is the following review paper: Savvas, D., 2001. Nutritional Management of Vegetables and Ornamental Plants in Hydroponics. In: Dris, R. Niskanen, R., and S.M. Jain (Eds). Crop Management and Postharvest Handling of Horticultural Products. Volume I: Quality Management. Science Publishers, Enfield, N.H., U.S.A.: pp. 37-87. -                      Students will be asked to read five statements regarding the management of nutrition in soilless culture and mark them as correct or false based on their knowledge. No justification is needed for their answers. Each successful answer will be evaluated with 4 points, each unsuccessful answer will be evaluated with -2 points, while no answer will receive no points. The primary source of knowledge needed to answer to this question is the following review paper: Savvas, D., 2001. Nutritional Management of Vegetables and Ornamental Plants in Hydroponics. In: Dris, R. Niskanen, R., and S.M. Jain (Eds). Crop Management and Postharvest Handling of Horticultural Products. Volume I: Quality Management. Science Publishers, Enfield, N.H., U.S.A.: pp. 37-87. -                      Students will be asked to answer to a question regarding the irrigation of soilless cultivations. The question will be evaluated with a maximum of 8 points (grading scale 0 – 8). The primary source of knowledge needed to answer to this question is Chapter 9 (Irrigation Control in Hydroponics) of the book “Hydroponic Production of Vegetables and Ornamental Plants”, edited by Savvas, D. and H.C. Passam, 2002. -                      Students will be asked to read three statements regarding the closed soilless culture systems and mark them as correct or false based on their knowledge. No justification is needed for their answers. Each successful answer will be evaluated with 4 points, each unsuccessful answer will be evaluated with -2 points, while no answer will receive no points. The primary sources of knowledge needed to answer to these questions are Chapters 7 (Nutrient Solution Recycling) and 8 (Nutrient Solution Disinfection) of the book “Hydroponic Production of Vegetables and Ornamental Plants”, edited by Savvas, D. and H.C. Passam, 2002.