Final report for FS19-314
Sustainability in farmer practices emphasizes not just the inputs and methods of growing and how they impact harvest outcomes, but also economic and social sustainability of food systems. Reflecting this, there has been movement over the past several years to increase the availability of local produce and food products in both an effort to support local economies, as well as decrease the environmental burden of transporting food products around the world. At the same time, consumers have come to expect a reliable, year-round source of a variety of produce. Local food systems, then, must develop and implement sustainable methods to extend the growing season to meet market demand.
For vegetable growers in the Southern United States, particularly those in the sub-tropical climate of south Florida, season extension runs into several challenges unique to the climate. Production is highest during the winter months due to milder, drier weather. During the other half of the year, production dwindles as the summer months approach. Heat, humidity, and high amounts of rainfall contribute to the difficulty of growing during summer months. In particular, these environmental conditions contribute to significant pest pressure and susceptibility for disease which, in turn, cause significant challenges for growers using organic, sustainable practices.
Most vegetable growers in south Florida start their growing seasons in September, selling their first produce in early November. These growers often have to end their season in April, losing out on income for a significant portion of the year and contributing to growers’ economic insecurity during this time. This growing pattern hits small growers and urban growers particularly hard, as profit margins are small due to the capacity of growers and the high price placed on land in urban and sub-urban areas. Season extension would offer these growers a means of increasing their economic sustainability by maximizing the time they are able to grow and sell their crops. At the same time, availability of local produce for a greater portion of the year would help increase market demand for local produce, increasing both economic sustainability of local growing practices, as well as having the improved environmental sustainability that comes from sourcing produce from local growers.
Many season extension methods have been used effectively across the country. For much of the country, season extension involves counteracting the effects of cold weather and frost. For vegetable growers in south Florida, season extension must counteract rising summer temperatures, heavy precipitation, and the resulting increased humidity. One possibility for season extension in the Southern U.S. and south Florida in particular involves the use of high tunnels, offering several potential benefits to south Florida growers. First, high tunnels counteract heavy summer rains by allowing growers to control the amount of water reaching their plants. In doing so, growers minimize the risk of flooding out crops during heavy summer downpours that can result in plant loss.
Second, the ability to limit the water that reaches the plants by decrease both disease and pest pressure. Limiting the variability in the amount of water reaching plants allows for appropriate, consistent irrigation under a grower’s control. This consistent irrigation then contributes to optimal plant development, which in turn increases plants’ resiliency in the face of diseases and pests.
Third, compared to other structural options for season extension (e.g., full greenhouse set-ups with temperature and humidity control), high tunnels have lower start-up costs, offering affordability for growers who are looking for ways to extend their season. This is particularly true for growers working in smaller farming operations who may not be able, within a reasonable time frame, to earn back the capital required to establish more extensive set-ups. Thus, high tunnels offer an economically sustainable option for growers from smaller operations. Similarly, high tunnels are more easily installed over a larger area compared to a greenhouse, further increasing their economic viability for many different operation sizes.
Our project had the goal of observing whether the use of high tunnels extended the growing season of cherry tomatoes in South Florida.
Our project illustrated that high tunnels did not increase the duration of the growing season, but did decrease the occurrence of pests and disease on cherry tomatoes.
- 30’ x 65’ Jaderloon High Tunnel (includes clear plastic covering)
- Sun Gold cherry tomato plants
- 1 ton of 5-4-3 Harmony organic fertilizer
- drip tape
- plastic mulch
Sun Gold Cherry tomatoes were planted at our farm in Miami Fl from September- July. An equal number of plants were planted in an open field and in the high tunnel.
The data that was recorded was fruit yield and disease/pest damage.
The main pests that we were concerned with were stink bugs, leaf footed bugs, and tomato horn worms.
We documented pest occurrence by noting any damage to the tomato plants. Fruit yield was recorded by weighing the tomatoes we harvested from both locations ( open field and high tunnel).
Results and Discussion
The results of our study on cherry tomatoes illustrated that high tunnels had certain benefits, namely decreased pest and disease pressure. We saw a 15% decrease in the occurrence of bacterial spotting and a 20% decrease in the occurrence of pest damage to plants, compared to open field growing.
From the 240 tomato plants in the open field and high tunnel trial, tomato production was right around 50lbs per week for both open field and high tunnel, from November-April. After April, production dramatically decreases to 15lbs week.
We did not see the growing season extended by the use of high tunnels or an increase in fruit yield.
Due to the high temperatures in the summer months, flower production from the tomato plants decreased (compared to December-April). Decreased flower production led to decreased fruit production during the later summer months.
Overall, cherry tomato fruit production in the summer did not increase using high tunnels, but high tunnel use during the normal growing season (September –April) is a great option.
Another option is to possibly use dark shade cloth and fans to decease the temperate in the high tunnels so that the tomatoes can produce during the hottest months of the year. One would have to consider what percentage of shade (i.e 20% vs 55%) would be suitable to allow the tomatoes to grow while also limiting the heat that enters the high tunnel.
Educational & Outreach Activities
We partnered with Florida International University and their Veterans Farmer program. On at least five occasions we had veteran farmers come to the farm and observe and compare the growing methods of open field vs high tunnel cherry tomato production.
Furthermore, participants actively took part in harvesting tomatoes, which further illustrated any differences or similarities.
It was easy to see that participants were less affected by heat and weather when they worked under the high tunnel.
Our project may have presented an eye-opening look into how high tunnels can decrease pesticide, fungicide, and bactericide use on organic farms. Just due to the decreased pest and disease pressure, we were able to inform participants of how manageable tomatoes become during the height of the season.
Normally tomatoes are some of the most pest-ridden crops on organic farms. The pests and diseases they contract spread to a number of other crops such as eggplant, okra, and peppers.
Just by the use of high tunnels, participants witnessed how a normal pest-attractant like tomatoes, can be turned into a more reasonable crop to grow and also allow for other crops to be grown without the added pressure of further pests and diseases.
One specific example of a farm that adopted the use of high tunnels after visiting our test site is Semillas Co-op. Diana Perez (of Semillas Co-op) liked the way they allowed tomatoes to be picked in the rain and how they decreased pest pressure.