Example II. A more complex science curriculum that could be used for college, high- or middle-school students that would introduce discovery, learning, and fun:
(This curriculum was based on a pilot study that I did with a high school for his senior science project and could be easily adapted to younger students as well)
(Presenters would need to provide the following background)
Aquaponics is an eco-friendly farming practice that uses sustainable methods to produce natural healthy food without chemical fertilizers. Aquaponics combines two- well-established practices of aquaculture & hydroponics to grow food in a closed-loop system that reduces the use of water resources, is soil-independent, & produces high yields of organic fish, vegetables, fruit and herb crops. Unlike conventional gardening, aquaponics offers a wide diversity in growing medias and conditions (with respect to water chemistry) that can be customized for the optimal growth of different plants. In addition, a variety of different mechanical systems can also be used to grow plants (NFT, Flood and Drain, & Raft), each of which may be more conducive for specific plant species.
An example of a recent case study:
Working with one high school student , we tested the growth of wheatgrass in different plant growing media using either a RAFT system, or two different Flood and Drain systems (i.e. either a timer-controlled draining system or a bell siphon activated draining system). We also compared the growth of wheatgrass in aquaponics to that of conventional gardening by growing the wheatgrass in soil, plus or minus the addition of fertilizer once per week.
Materials and Methods:
One of our main interests was to test cheaper media alternatives to hydroton, a typical commercial standard media which is expensive and is less sustainable since it is not made locally. The media that we tested was also very different in their chemical and physical properties and we were interested in determining whether this would make a difference in plant growth. We tested the following medias: (1) a mixture of sand, clam shells, and absorbant; (2) permatill (or expanded shale); (3) hydroton with the addition of different types of biochar.
Each of these media offer different potential benefits. We chose the sand, clam shells, and absorbent mixture since these materials absorb water more readily and may provide an additional calcium and nitrogen source to plants. We hypothesized that this media may help the plant stay moist during the long drying out periods that occur during the Flood and Ebb cycle and may also provide nutrients that sometimes become limiting in an aquaponic system. We chose permatill because it is commercial available and cheap, provides a substrate that is more chemically basic in nature than the other growing medias, and is known to bind microbes well due to its relatively high surface area. We chose Hydroton with or without the addition of 3 different Biochars- Biochar made from Bone, Coco, and Oak. Biochar is charcoal made from renewable plant material and is thought to aid in plant growth by providing a good substrate for the growth of beneficial bacteria and is an eco-friendly material since it also acts as a carbon sink by binding Carbon dioxide. Hydroton also is a great substrate for its biofiltration capacity.
We also wanted to determine if wheat grass would grow better in an aquaponic system where water was provided continuously verses one where the plant had a drying out period. In the RAFT system, we grew the wheatgrass by floating it in media on the top of water that was being aerated to drive oxygen into the root zone, preventing root rot. In contrast, in the Flood and Drain system, we grew wheatgrass in media and flooded it with water and then subsequently drained it or a particular period of time before the next flood cycle. In our system, the timer-based draining system provided a longer drying out period than the Bell-siphon flood and drain system.
In order to ensure that all the plant beds were receiving the same amount of nutrients from the aquaponic system so that they could be directly compared, we used one fish tank as the source of water for all the beds. As a negative control we decided to grow the plants in water alone, to determine if the fish were indeed required as a nutrient source for plant growth.
To provide sufficient statistically sampling, in each aquaponic system we planted 4 pots with each media tested and in each pot we planted 4 seeds. As a positive control, we planted seeds in dirt plus or minus fertilizer every week. We charted growth of the tallest plant in each media sample over time to determine its growth rate and sacrificed some of the remaining plants to analyze their root growth. To analyze the data to determine which media and system was the best for the growth of wheatgrass, we decided to calculate the growth rate instead of just overall growth. Determination of the amount of growth as a function of time between samples is more accurate than comparing growth alone since seed germination times and differences in planting depth between samples can vary. For example, one plant may be taller than the next, not because it grew better, but because the seed germinated faster or the seed was closer to the surface when it germinated. By calculating how fast the seed grows overtime, a more accurate reflection of growth will be achieved. At the end of the experiment, we also cut back the plants to calculated their re-growth in different media and systems which would also be a reflection of their overall growth properties. We also analyzed the ratio of root growth to shoot growth to determine if root growth was related to growth rates.
The high school student that I was working with was a natural scientist. He grabbed the concepts of good experimental design, and positive and negative controls easily. Through out the experimental exercise, many questions arose in relation to how to think logically and what questions are important to ask during the process of experimentation. For example, what is the best way to measure consistently, how often should we do sampling and how many samples should we take for it to be statically relevant, and once we gather a large amount of data how do we interpret and report it so it can be understood easily by others.
The results of the initial growth rate of wheatgrass in the various systems and media are shown in Figure 1-2. We found that there was not a significant difference between flood and drain using a timer versus a bell-siphon so only the results of the bell siphon are shown for simplicity. Cutting the wheatgrass and analyzing regrowth did not change any of the experimental outcomes and therefore these results are also not shown for brevity.
The student was especially excited when he discovered at the beginning of the experiment that although all the growth rate of the wheatgrass didn't differ dramatically between the media or the growing method (Raft vs Flood/Drain), the roots of the plants grown in sand/absorbent/crab shell mixture were 5-10 x smaller than roots grown in the other media! He quickly started to hypothesize on why this might be the case and what he thought might happen as the experiment continued.
He asked scientific questions like:
1. If the roots did not grow as well in this media (SAC), would this eventually cause the shoots to have a slower growth rate over time making the plant eventually smaller in comparison to the other plants growing in different media?
2. Or is the SAC media a better substrate for binding nutrients and therefore a large root system would not be required for optimal growth in this type of media over time (a media property in the literature referred to Cation Exchange Capacity)?
3. Was the sand, absorbent, or crab shell responsible for this decrease in root growth or was it a combination of the two or three?
We found that the shoots of the plants growing in SAC continued to grow as quickly as the other plants yet the roots still remained small. We then repeated the experiment using different combinations of sand, absorbent , and crab shell to determined which component was responsible for this effect and we were both surprised that the experimental result was not reproducible. Watch this student live as he works through the scientific process to understand why this happened :
Even though the experiment showed that different Aquaponic growing systems and the various media tested didn't have a considerable effect on overall growth of wheatgrass, the results using a different crop such as heavy feeding plants like tomatoes may show a growth difference with respect to these variables. Biochar seemed to inhibit growth initially but overtime its presence was beneficial (presumably because it has strong nutrient binding capacity and needs to come to equilibrium before it can enhance growth). Sand by itself did not support growth and needed to be mixed with other media to allow wheatgrass to grow effectively. It was also interesting to note that crab shell can reduce overall growth of roots if unwashed but does not inhibit the overall shoot growth. Therefore it may be beneficial for used in an aquaponic system where plants are more susceptible to becoming root bound. It remains to be proven whether it was the salt on the crab shell that caused the stunted root growth. (Crab shell also attracts bees like mad so watch out!! ) Overall, my student said that his favorite part of the experiment was eating his experimental subjects and felt empowered that he had the skills and knowledge to grow his own food in the future.
This was an ambition project for one student and could have been adapted easily to a classroom project with 3 groups of 7 students each. Each student group could be in charge of one aquaponic system (RAFT, FD with Bell-siphon, FD with timer-base shut-off). In each group, each of the 7 students would be in charge of a different media. The teacher would be in charge of the positive and the negative controls. The students could then compare their results in a collaborative effort.
What students could learn from this type of experiment using Aquaponic as a model learning system :
I. How to design a sound experiment by introducing the student to the following topics:
A. Decreasing variability through proper experimental design.
1. Planting all seeds at the same depth
2. Running all systems off the same aquaponic tank to decrease variability in the supply of nutrients
3. Setting up systems so all samples receive the same amount of light
4. Measuring growth from the same starting point (top of plant pot) and choosing the best seedling to measure and track.
B. Understanding positive and negative controls in validating experimental hypotheses.
1. Positive control- Testing the wheatgrass growth in a conventional soil-based system and asking whether adding fertilizer increases its growth.
Question: How does the addition of commercial fertilizer compare in nutrient content to the natural level of fertilizer provided by the fish in the aquaponic system?
2. Negative control- Testing whether a wheatgrass seed can germinate in water alone compared to nutrient rich water.
Question: Why can large seeds sprout in water alone and can they continue to grow in water alone if cut back and left to regrow?
C. Proper sample size determination
D. Observing plant characteristics like plant color, size, and other appearances that might give an indication of its overall health.
II. How to interpret scientific data and compare the results accurately:
A. Calculating Growth Rates instead of overall growth
B. Calculating Root growth in relationship to plant shoot growth (dry weight)
C. Calculating the amount of fertilizer being provided by the aquaponic system using water chemistry testing
D. Representing results using Bar and Line graphs using Standard deviation and Mean averages
E. Hypothesis creation based on Experiment Results
For example, asking questions like:
1. Is there a difference in growth rates between different media and systems? Why?
2. Is there a difference in root formation between different media and systems? Why?
3. Are there clues in the literature that might explain the results? Is there a way to test your new hypothesis?
F. Designing experiments to test new hypotheses
III. Science and Skills learned in project :
Introduction to the following subjects :
Plant Biology (photosynthesis and respiration, cold & warm varieties, light and heavy feeders)
Fish Biology (respiration and cold/warm varieties)
Nitrifying bacteria and the Nitrogen cycle (establishing aquaponic tanks)
Media and Soil properties (e.g. Cation exchange capacity (CEC) & particle size)
Water chemistry and testing (e.g. pH, Buffering, and nutrient concentration determinations)
Mechanical design and plumbing (e.g. bell-siphons, bulk-head fittings, aerators, pumps, PVC and bed construction)
Balancing the system using Feeding Rate ratios and calculating Biofiltration Capacities of media
Scientific interpretation of results
Hypotheses testing and researching topics
Analyzing and charting data
Introduction to Agribusiness principles with respect to Aquaponics such as ROI (return on investment), start up costs, consideration of energy costs and alternatives,
estimating Plant Crop Yields and Market sales.
IV. Having fun and learning to grow their own food sustainably:
Planting, harvesting, preparing, and selling and/or eating their crops!
For examples of slide show workshops please inquire by email.
The Ultimate Goal of the Educational arm of my business is to link Healthy food to a Healthy community to a Healthy nation! Aquaponic is a project-based learning tool that can help students understand the importance of future sustainability while becoming critical thinkers in the process.
Since Aquaponics itself is a new agribusiness technology, and there is such variability in the system design, it lends itself as the perfect teaching model to engage students in the process of scientific discovery. Aquaponics is the perfect tool to teach students basic biology, chemistry, mathematics, and mechanical engineering, while also offering students a practical side of learning by teaching them how to become self-reliant and environmental responsible with respect to growing their own food in a sustainable way. It doesn't require a greenhouse or land, and instead can be taught by simply using a small table-top Aquaponic unit in the classroom in a limited space! Learning these skills will not only absorb young people in the excitement of science but will also give them life skills to make them self-reliant and healthier!
Unlike cookbook experiments that merely rehash the work of others, students can be creative and ask a variety of experimental questions that have yet to be answered using Aquaponics as their model system. For instance, a whole slew of experiments can be carried out comparing the growth of different plants in different media using different mechanical aquaponic systems. Changing the water chemistry and temperature offers addition opportunities to experiment with this system to grow different plants and fish species . Since the experimental questions surrounding these different growth parameters are endless, with some guidance from their teachers, students can be directly involved in determining the scientific direction they want to pursue which will surely spark their imagination. The students can then analyze their experimental findings and research the literature to support their results. If their findings create a new hypothesis they can continue to test their new theory(s) in the second half of the course. The hope is that this type of project-based learning model will engage students scientifically and could even lead to undiscovered knowledge moving the field of aquaponics forward!
A long term goal of mine is to provide students and teachers with different curricula packages that they can choose from to ask a variety of experimental questions that have yet to be discovered in Aquaponics. Once they commit to pursuing a specific line of experimentation, they can then upload their results in an online scientific forum available through my website. Experimental results can then be compared from school to school until a consensus of the results are met. Although each school is limited in the sample size to the amount of the data collected, by adding and contributing their results to this global data base, a more complete sampling of the results will lead to an increase in precision of these unknown parameters, making the overall experimental results more reproducible and considered more scientifically sound.
Example I. A simple curriculum to start with for students of all ages:
1. Students will learn to read food labels and learn the difference between healthy food verses "junk" food (e.g. what is fructose corn syrup and why is too much a bad thing).
2. Students will learn what healthy food does for their bodies (e.g. what are vitamins and why are they essential for a healthy diet).
3. Students will be provided with a basic lesson on organic Aquaponic growing, and why it is a sustainable ecosystem.
4. Students will build, plant, and grow food in a simple classroom table-top Aquaponic unit that they can learn to build at home. (They will start by growing healthy and fast growing wheatgrass plant for quick gratification).
One week later:
5. Students will learn how to harvest and prepare a wheatgrass high energy smoothie in class so that they can relate that growing healthy food is something that they desire (reward system) and that if they want to enjoy this type of food again they have to go out into their garden at school (or at home) and work to grow it again (farm to fork concept).
6. Students will trace the ingredients of a basic meal back to their origins in the soil to make the connections between food, agriculture, and ecosystems. Students will learn about the challenges of growing food: healthy soil, access to freshwater and land, organic verses pesticides and herbicides, etc and how healthy ecosystems are required for a healthy food chain. They will explore how Aquaponics can address and solve some of these agricultural and environmental challenges.
The lesson plan is a simple curriculum that is based on having fun. By simply planting food and eating what they grew in less than a week, with a minimal amount of time investment from the teachers and the students, it will drive home the lesson that when they eat well, they will feel well and that it is not difficult to grow healthy food. Most importantly they will learn how organic food is important for their health and the earth's sustainability.
'We have schools because we hope that someday when children have left schools that they will still be able to use what it is that they've learned. And there is now a massive amount of evidence from all realms of science that unless individuals take a very active role in what it is that they're studying, unless they learn to ask questions, to do things hands-on, to essentially recreate things in their own mind and then transform them as is needed, the ideas just disappear.'
Roots 15x shorter in SAC!
Figure 2- Comparisons of root length of Wheatgrass grown in different media before and after washing the crabshell.
As shown above & in Figure 2, we were surprised to find that the roots of the wheatgrass plant were significantly smaller when grown in the sand/absorbant/clamshell mixture. Even though the shoot growth was similar in all media, roots grown in this combination media (SAC) were 5-10x times smaller in both the RAFT and BELL-SIPHON system! When we repeated this experiment after washing the crabshell media more carefully, we found that root growth was restored .
As shown in figure 1 there was not a significant difference in wheatgrass shoot growth when grown in a RAFT system verses a Flood & Drain Bell Siphon-based system. The wheatgrass seem to grow equally well in all media tested, favoring Hydroton initially. Interestingly, wheatgrass grown in soil that was treated with Miracle Grow fertilizer weekly grew at a similar rate as wheatgrass grown in an aquaponic environment. (In fact, when the nitrogen levels in the recommended Miracle Grow fertilizing solution were tested, they were equal to that of the levels in the fish tank water!) When wheatgrass was grown in soil that was not fertilized, it grew poorly and its growth was equal to that if grown in water alone, showing that soil is only a good media if replenished over time with nutrients. Notice that the growth rate of all samples slowed down overtime and eventually the wheatgrass overall height equalize across medias after 14 days.
Figure 1- Comparisons of Wheatgrass grown in different media in a continuous flow RAFT system or a flood and drain Bell-Siphon system