The greenhouse hydroponic vegetable industry in Florida has changed significantly over the past 15 years (Tyson et al. 2004; Tyson et al. 2001) due to shifts in market demand, adverse weather, and research-based innovations in new crops, as well as improvements in production cost and efficiency (Resh 2004; Shaw and Cantliffe 2002; Shaw et al. 2000; Stapleton and Hochmuth 2001; Sweat et al. 2003).
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Rockwool culture (Figure 4) was the most common hydroponic production system in Florida during the 1990s. Rockwool is an inert, fibrous material produced from a heated mixture of volcanic rock, limestone, and coke. Rockwool is extruded as fine threads and pressed into loosely woven sheets. Use of rockwool declined in favor of perlite primarily because of the greater cost of materials and the difficulty of disposal; in both of these areas, perlite has an advantage.
In most hydroponic production systems, at least two fertilizer stock tanks are needed. One tank contains calcium nitrate, and the other contains a "premix" of a complete package of nutrients without calcium. Large growers often choose to mix their own fertilizer batches with individual ingredients to reduce cost.
While this publication generally focuses on information for greenhouse hydroponic production systems and crops, growing vegetables in greenhouses during the summer months in Florida can be problematic due to heat, humidity and pest buildup that can occur. Additionally, prices for vegetables are usually low during the summertime.
For these reasons, most hydroponic growers in Florida spend the hottest summer months cleaning up the old crop, sanitizing, and preparing for the new crop. If all plant material is removed from the greenhouse for a month or two, any remaining pests are likely to starve for lack of food, and the grower can then start with a clean house for the fall crop.
Food security is a growing global concern. To meet the needs of an ever-growing population, food production practices will need to evolve to maximize food quantity and quality. Controlled-environment food production has increased significantly in the United States over the past 5 years, and a component of that production includes hydroponic food crops. In an effort to better prepare a workforce with knowledge of hydroponic crop production, a new course was added to an existing greenhouse curriculum. A service-learning project was integrated in the course that allowed students to experience both growing crops hydroponically and volunteering at a local food bank with a free meal program. Self-assessment showed a significant increase in student confidence in understanding food security by the end of the course. There was also a significant knowledge gained in defining terminology, factors, and the impact of food security in a community. The three guided reflections students completed during the course identified four common themes relative to the course content and service-learning project including the following: community benefits, value of volunteering, local and global effects of food insecurity, and personal growth.
Food security on a global and local level is becoming increasingly discussed. The ability to meet food security and nutrition goals require food to be available, accessible, and in sufficient quantity and quality to meet the demand of an ever-growing population and is a critical issue (Food and Agriculture Organization of the United Nations, 2015). Also, a recent study shows poverty is increasing substantially in urban areas, with a majority (>56%) of impoverished now living in urban areas (Eigenbrod and Gruda, 2015). Urban agriculture can contribute to food security in these impoverished areas by improving availability and access to nutritionally dense foods (Badami and Ramankutty, 2015; Orsini et al., 2013). In addition to traditional food production methods in urban areas, food crops produced hydroponically in controlled environments can result in food that is accessible and of high quality (Premanandh, 2011).
The combined retail and wholesale value of food produced in a protected culture, including greenhouses using hydroponic systems, has increased by $243 million (44%) between 2009 and 2014 (U.S. Department of Agriculture, 2009, 2015). Hydroponic and controlled-environment food crop production provides opportunities to improve the quality and yield of the crop by manipulating environmental conditions and cultural practices (Krauss et al., 2006; McAvoy et al., 1989; Wu et al., 2004). In addition to predictable yields, quality produce, and value-added food crop production, hydroponic production systems can lead to increased food security. For example, hydroponic and controlled environment agriculture can improve year-round availability of and increase proximity to safe and nutritious produce (Premanandh, 2011). Depending on their design, hydroponic systems may incur significant capital investments; however, simplified hydroponic systems offer low-cost solutions that can increase the accessibility to this production method and the resulting produce (Izquierdo, 2007).
To support and manage this increase in hydroponic crop production, undergraduate greenhouse curricula should include education and training techniques in hydroponic production of fruit and vegetable crops. Shoulders et al. (2016) surveyed 110 four-year colleges and universities across the United States to determine the prevalence of hydroponic and greenhouse food crop production courses. They reported only 4 courses of the 84 courses related to greenhouse production focused on greenhouse food crop production. There is clearly a need for more curricula to include greenhouse food crop production.
Craver and Williams (2015) suggest hydroponic production modules could be developed and incorporated into existing greenhouse or fruit and vegetable production courses to further increase student knowledge and awareness of greenhouse food crop production practices. Greenhouse crop production courses primarily focus on the technical aspects of producing food crops in controlled environments. We believe that coupling the technical aspects of hydroponic crop production with engaging learning strategies such as hands-on laboratory exercises and service-learning projects may create a richer learning experience for students.
The curricular need for a hydroponic food production course at the Iowa State University created an opportunity to develop a new course with an extensive laboratory component to produce food crops hydroponically and to integrate an associated service-learning project. Our objective was to create a course that directly connected course content (the technical aspects of hydroponic crop production) to a service project that increased student understanding and awareness of food security issues in their community and globally.
The lecture content is divided into three sections. The first section introduces the history of hydroponic food crop production, the current state of controlled-environment agriculture, and the hydroponic systems most frequently used. The second section of lectures focuses on the principles of hydroponic food crop production, including water quality, mineral nutrition, light, temperature, carbon dioxide, and pest management. The final section features crop-specific lectures on growing tomato (Solanum lycopersicum), pepper (Capsicum annuum), cucumber (Cucumis sativus), lettuce (Lactuca sativa), culinary herbs, and strawberry (Fragaria ananassa).
The laboratories focus on producing hydroponic food crops using nutrient-film technique (NFT) systems, deep-flow technique (DFT) systems, double rows of coconut slabs, and double rows of Dutch buckets (Currey, 2016; Jones, 2005; Resh, 2013). Lettuce was grown in both NFT and DFT systems and herbs were grown in the NFT systems. Tomato and cucumber were each grown in Dutch buckets and coconut slabs.
The service-learning community partner was Food at First, a local, nonprofit meal program and food bank. When lettuce, herbs, tomatoes, and cucumbers matured, students harvested these crops, and packaged them for delivery and distribution to the food bank, and for use in the free meal program. Crops were harvested weekly as part of laboratory activities. Because the delivery would frequently occur after the laboratory period had concluded, participation in the delivery process was optional for students.
In addition, students participated in volunteer activities at the food bank during a period in the middle of semester. Volunteer activities included one of the following three different experiences: 1) assisting with food distributions at the food bank; 2) assisting with the preparation of meals for the free meal program; or 3) assisting with serving and cleaning up for the free meal program. When possible, the crops the students produced were incorporated into the meals prepared for the free meal program. Students were required to participate in one volunteer shift in 2014, whereas in 2015 students were asked to participate in two volunteer shifts. Students chose which type of volunteer experience(s) they wanted to participate in.
Pre- and postsemester self-assessments related to food security (1 to 5 scale) from students enrolled in a hydroponic food crop production course in 2014 (n = 25) and 2015 (n = 24) that included a service-learning component at a local food bank and meal program. Data were analyzed using a t test with an α = 0.05 and the significance (Sig.) is reported.
A number of students also expressed a desire to be able to distribute the produce directly to the Food at First clients as a means to more fully connect with their service, laboratory, and class experiences. Students who did get to serve the food described very positive experiences. For example, students who volunteered in a food-serving role indicated they were able to explain to other volunteers and attendees how hydroponics work and how they grew the food.
The service-learning component of the course was successful in directly connecting course content to increased student understanding and awareness of food security issues in their community. The self-assessment, quizzes, and reflections show both knowledge gains relative to course content and personal growth in this hydroponic food production course. Having a well-defined service-learning project with clear expectations and a strong working relationship between the community partner and faculty member helped ensure all parties involved had a beneficial experience. 2ff7e9595c
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