Final report for FW20-367
Flagstaff, Arizona is a growing city with an increasing demand for local produce. Despite the city’s steady growth, farms and producers in the region remain scarce. This is largely the result of limited and expensive farmland and poor soil, forcing many growers to be creative with small plots. From an ecological and sustainable standpoint, it can be difficult to grow in Flagstaff, as there are limited water resources, making water conservation a critical issue. Many communities across the United States face these realities as well. In addition, most native fish species in Arizona are either threatened or endangered. Our project will develop techniques for sustainable and profitable aquaponic growing of a marketable product while assisting in the conservation of rare native fishes. Space efficiency, water conservation, increased crop yields and native fish conservation are the primary goals. We will show the differences in production and water usage in systems with and without fish and compare them to in-ground growing. By rearing Roundtail chub (Gila robusta) in our aquaponics treatments, we will help protect an important native species in our region, while also providing an example for how farmers can help to achieve local and state conservation goals. There are no examples of this type of growing in our community and our project will develop a model for producers to learn about the benefits of aquaponics and rare species conservation. Our results will be shared with the community, schools, and producers through organized farm tours, workshops, presentations and educational pamphlets.
We will develop aquaponic growing techniques, with space efficiency, water conservation, native fish preservation, and increased crop yields our primary objectives. This project will develop a sustainable example for growers in land limited, arid regions to produce leafy greens while increasing overall productivity and sustainability on their farms. Using an existing high tunnel, we will design space efficient, tiered systems; these will include tanks for rearing fish and two levels of growing space dedicated for intensive leafy greens production. Our yields from these systems will be recorded and compared to in-ground growing. Fish growth will also be monitored and recorded. These self-contained systems recirculate and reuse water creating dramatic decreases in overall water usage compared to in-ground growing. We will record water usage throughout our project and compare the overall water usage from each experimental treatment. Using aquaponics to rear a native fish species for conservation purposes will provide additional specimens for research and conservation purposes while providing an example of how famers can contribute to environmental or conservation goals. At the end of the project, fish will be provided to the state wildlife agency for use in research or conservation projects in our region.
- - Producer
- - Technical Advisor
Our project consisted of three treatments (each with 3 replicates), an aquaponic treatment with Roundtail chub, an identical treatment without fish, and a separate in-ground treatment using standard growing techniques. All Treatments were conducted in a portion of a high tunnel greenhouse (26ft wide by 72ft long) at Forestdale Farm in Flagstaff, Arizona. For our aquaponic treatments, we constructed six identical artificial streams. These stream systems functioned independently of one another, with half containing fish and the other half without fish. Each replicate consisted of a 200-gallon fiberglass tank (9ft L X 3ft W x 2ft D) which we modified to be safe for fish. In the tanks there was a small magnetic drive pump to circulate water. An additional pump (Evolution ES3500) and bead filter (EBF1000 filter) was set up and used for biological filtration. This pump assembly also had a diverter valve which connected to a screen filter and garden hose for overhead watering. Water was constantly pumped through the bead filters and cascaded back into each tank; when we needed to water we would open the valve to divert the water from each tank. An oxygen diffuser (aquascape pro air pond aerator) was added to each tank to supply extra dissolved oxygen, especially critical for treatments containing fish. These components helped transition the tanks into recirculating artificial stream systems, mimicking natural streams which are suitable for rearing fish. Above each tank we had two tables. One table rested directly on the tank while the other table was slightly smaller and rested 1ft above the tank. Each table was able to hold 6 flats of 4-inch pots (total of 108 pots) and 6 flats of 6-inch pots (total of 36 pots). We recorded the yields of each pot size separately to understand the difference between container size. Each pot was filled with a standardized potting mix, mixed on the farm from coconut coir, perlite, vermiculite, and 1 cup of standardized organic fertilizer per cubic foot. For each treatment an entire table was planted each week consisting of two flats with 4-inch pots and two flats of 6-inch pots of arugula, kale, and lettuce. Once the tables were full, we replanted at each harvest so the system maintained full production. Plantings took place from June-September. Seeding was standardized by weight and direct seeded by hand. After seeding, flats were placed on the lower tables to germinate. After one week the plants on the lower table were moved to the upper table where they remained until harvest 35 days later. Plants were watered from the diverter valve connected to the pump and filter assembly as needed. The valve had a screen filter to catch debris and a short hose with a misting nozzle. Each treatment was kept separate and watered from the individual tanks. Excess water from irrigating drained back into the tanks. Each tank in the aquaponic treatments with fish was stocked with 625 juvenile Roundtail chub produced from broodstock held at the US Geological Survey aquatic research laboratory operated by David Ward in Flagstaff, AZ. Fifteen fish per tank were tagged with a Passive Integrated Transponder (PIT) Tag so that an accurate growth estimate could be obtained for fish over the entire growing season. These fish were measured before putting into the tanks and again at the end of the project. Fish were fed ad-libitum daily with a standard hatchery ration of organic fish feed (Aquamax 200 or 600 pelleted feed). At the end of the experiment fish were returned to the US Geological Survey for use in appropriate research and conservation activities. For the in-ground treatment, we dedicated two grow beds consisting of the same square footage as the tank treatments. The in-ground beds were used for intensive leafy green production and planted following the normal protocol of Forestdale Farm. We direct seeded 1 bed of arugula, kale, and lettuce, harvesting at maturity, and rotating and replanting throughout the season. Beds were amended with applications of aged compost in the spring prior to planting. We weighed the harvests from each treatment throughout the season. This data was used to compare the overall yields of each tank treatment to inground growing practices. Water usage was recorded throughout the experiment and compared across all treatments.
Kale Results: Our kale (grown as baby greens) results show that the most productive system was the tiered tables with fish in the tanks using six-inch pots. Over a 35-day growing period these systems yielded an average of .39 pounds per square foot of growing space. In these same systems (tiered tables with fish) four-inch pots yielded similar results with .34 pounds per square foot. Though lower in overall yields, the difference between four-inch pots and six-inch pots was not enough to warrant use of the larger pots (average difference of .05 pounds per square feet). The tiered growing tables without fish yielded significantly less, .13 pounds per square foot for four-inch pots and .15 pounds per square foot for six-inch pots. This is a significant decrease and these systems without fish are not an advisable means for leafy greens production. The in-ground harvest of kale produced an average of .24 pounds per square foot. When running statistical analyses on the data of yields of 40 individual pots per treatment we found that kale results were significant statistically (with a Prob>F of <.0001). Kale growth increased with the addition of fish nutrients compared to treatments without fish (p<.0001, Oneway Analysis of Variance). On average kale production increased by 0.300 lbs. per pot for four-inch pots and 0.302 lbs. for six-inch pots. In comparison to the in-ground plot, kale production with fish nutrients was less pronounced, but still increased on Average by 0.20 lbs./pot, when compared to 6 -inch pots with nutrients. In conclusion, the tiered table set up with fish proved to be the best option and yielded the highest pounds per square foot. Forestdale Farm. Greens Graphs
Lettuce Results: Lettuce yields followed a similar pattern as Kale but with a greater difference between the treatments with fish versus treatments without fish. In addition, with lettuce there was a noticeable difference between four-inch pots and six-inch pots. Over a 45-day period the six-inch pots with fish had an average yield of .53 pounds per square foot while four-inch pots with fish yielded .36 pounds per square foot. This difference is significant enough to warrant the use of 6-inch pots for lettuce production. In-ground average yields were .47 pounds per square foot which is comparable to the six-inch pots with fish. The four-inch and six-inch pots without fish yields were .05 and .08 pounds per square foot. Again the results proved to be highly significant statistically (please see attached graphs for more details). The best method for growing lettuce was the tiered table system with fish using six-inch pots. Forestdale Farm. Greens Graphs
Arugula Results: Arugula followed the same pattern for pot size with six-inch pots with fish yielding an average of .32 pounds per square foot and four-inch pots with fish yielding .24 pounds per square foot. However, (as opposed to kale and lettuce) the in-ground yields for arugula were higher, averaging .38 pounds per square foot. Though the six-inch pots with fish and the in-ground treatments were similar in yields, the in-ground arugula was of a better quality. Even in the six-inch pots with fish the arugula seemed stressed and did not seem to do well in the pots. Arugula was grown over a 35-day period. (Please see attached graphs) In conclusion arugula seems to do better inground then in pots. Forestdale Farm. Greens Graphs
Water usage: Overall water use per square foot was similar throughout the experiment between all treatments. Looking at the averages for June-August in gallons per square foot per day, in-ground growing used .11 gallons, four-inch pots used .12 gallons per day, and six-inch pots used .10 gallons per day. The real difference comes when comparing water usage to yield per square foot. For example, kale in-ground treatments yielded .24 pounds per .11 gallons while the six-inch pots with fish yielded .39 lbs per .10 gallons of water. To put this in perspective, in the height of summer, it would take approximately 200 gallons more of water to produce 50 lbs. of kale in-ground versus the tiered growing tables with fish using the six-inch pots. Over a growing season this is a significant difference and growers in arid, or water scarce regions should give preference to this type of growing.
Roundtail chub growth: 625 juvenile Roundtail chub were added to each of the tanks for the replicates with fish. 15-20 fish per tank were tagged with passive integrated transponders (PIT). The total lengths in mm of these fish was recorded at the start and end of the 180 growth trail period. During this period fish growth was an average of 10.9 mm, with a range of 4mm-20mm. Other studies have shown that a 10 mm increase in size for these small chub can significantly reduce predation risk when stocked into the wild (Ward and Morton-Starner 2015). Predation relationships are very size dependent and even small increases in body size can lead to significant increases in survival and reduced predation risk for small fish. Roundtail chub growth Forestdale Farm
Education and Outreach
Our outreach goals were separated into three categories so the depth of information could be shared as suitable for each group. These categories consisted of information directed to the general public, in-depth discussion and presentations for university and school settings, and workshops and discussions for producers. Due to the COVID 19 pandemic we were very careful on the farm, limiting outside contact where possible, and developed safety precautions to minimize exposure and risk on the farm. With safety in mind, we limited public tours and workshops to small groups. We had two small tours early on in the season to discuss the project with interested public. In order to reach a larger audience, we decided to put together a detailed video about the project to be shared with the general public. This video was filmed in three parts to give the whole scope of the project. The first part was early in the experiment at Forestdale Farm and highlighted the set up and the experiment as a whole. The second part took place at USGS research facility where David Ward discussed Arizona native fish and the importance of conservation. The last part was filmed at the farm a few weeks later when the growth of plants in the project was clear and results were starting to come in. This video served to introduce the project and highlight the research that was being done. We shared this video with our community, universities, cooperative center, and other relevant organizations along with a brief survey that people could complete after watching the video. We also shared it with our email list, and on our FaceBook and Instagram accounts. We had lots of interest and positive feedback from the video and it proved to be a great way to reach a large audience in our community. The other main event for sharing project information with the public consisted of a reporter and photographer from Flagstaff’s local paper, the Arizona Daily Sun, coming to the farm for a tour. This resulted in an in-depth front page “Sunday Centerpiece” article. This article was a great way to get the public interested in the project and resulted in many emails and other productive communications. The public was very excited and provided positive feedback and support of the project. For the next outreach category, university and schools, we had tours with Coconino Community College (CCC) students as well as Northern Arizona University (NAU) students. The first tour was with NAU’s Sustainable Botany Class and we discussed aspects of the project related to their studies, specifically the biology of the systems. The second tour was with CCC’s STEM club, a science and technology club which was interested in starting its own small-scale systems. We went over the more technical aspects of the experiment and discussed the best ways for their class to implement an aquaponic project. In order to provide more detailed information to local growers we reached out to the “Flagstaff’s Growers Coalition” and set up a day for everyone interested to come out to the farm. This was a good way for growers to ask more detailed questions and get the specifics of the project. We went over equipment and set up as well as early results. We kept open communication with any interested growers in the region and followed up via email, Zoom, or phone to answer any questions about the project throughout the season. Some topics we discussed were the overall maintenance of systems, daily operation and troubleshooting, details of fish production, intensive leafy greens production, succession planting, and maximizing yields in small spaces. At the end of the project we presented a PowerPoint about the project and our results via Zoom at the “Small-scale farmers colloquium.”
Education and Outreach Outcomes
General notes on quality: Overall the crops harvested from treatments with fish as well as the in-ground treatments was high quality, suitable for all our sales outlets including high-end restaurants. In contrast, the yields from treatments without fish were more suitable to be mixed with other greens and for CSA distribution or farmers markets sales, and some of the arugula and lettuce was substandard and not sellable. Though the treatments without fish were useful for comparison, especially visually for presentation, they were not profitable for the farm since yields were minimal. For future research it would be more practical for farmers to use a standard organic fertilizer application on the treatments without fish. This would provide them with a marketable crop while also showing how much money can be saved on fertilizer use when incorporating fish into the system. Putting a metric on the cost savings of adding fish would be a powerful education piece for growers.
General notes on in-ground verses pots: Though in-ground yields were less, the benefit of the in-ground growing is that it is possible to get a 2nd and 3rd harvest on some of the greens, whereas only one harvest seemed possible with the potted plants. However, for the farmer limited on space, the tiered table set up with fish still proved to be the best option. In addition to a higher yield per square foot, this set-up also allowed for the space underneath the tables to be used and speeds up germination of the succession crop. The other benefit is that with individual pots it is easier to harvest smaller quantities. In addition, as soon as crops are harvested new ones can be planted so production can be maximized. With in-ground growing it’s difficult to succession plant until the whole bed is harvested, which makes small on-demand harvests more difficult. More research in the benefits of intensive, container-based growing would be beneficial and useful for small farmers.