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Written by Mary Hathaway, OFRF’s Research and Education Program Manager, and based on eOrganic Webinar by Dr. Zhao on Adapting and Expanding High Tunnel Organic Vegetable Production for the Southeast

I am excited to share some new research findings on high tunnel production for organic vegetables in the Southeast region. But before we get into those findings, let’s answer a couple of FAQs: what exactly are high tunnels, and why are they important? High tunnels (HTs), sometimes referred to as protected culture systems, are commonly used for season extension and/or production of high-value crops. High tunnels are increasingly being utilized by organic growers for their many benefits, such as crop protection and improved crop quality. While HTs are generally regarded as a tool for production management, they can also aid farmers with risk management and act as a resource conservation practice. 

One reason why high tunnel use may be growing in popularity is the availability of funding from the USDA-NRCS EQIP High Tunnel System Initiative. This NRCS program has been pivotal in providing the funding and support needed to access this season-extension tool that can be a real game changer for farm operations. As someone who has gone through the process first-hand of receiving and building a high tunnel, I can attest that the program is worth any of the front-end paperwork, and helps growers improve their infrastructure while gaining many positive ecological benefits. High tunnels can provide many benefits, including protecting your crops from extreme fluctuations in weather. 

Unique Challenges in the Southeast

While high tunnels may provide positive benefits, growers in the Southeast face several challenges when implementing HT in their growing systems. These challenges are typically related to airflow and managing excessive heat stress, humidity, pests, and diseases. I have experienced some of these challenges first-hand at my small-scale vegetable production farm in Central Florida. It is no easy thing to deal with the excess humidity and fluctuating pest and disease pressures, so I was excited to see new research led by Dr. Xin Zhao focused on “Adapting and Expanding High Tunnel Organic Vegetable Production for the Southeast” (more specifically, Florida and Georgia). This body of work is thanks to a collaboration by researchers from the University of Florida, the University of Georgia, Florida A&M University, and the USDA-Agricultural Research Service.

Findings

Temperature

Anyone who has ever stepped inside a high tunnel knows that air temperatures are higher inside HTs than outside. One part of this research study entailed comparing different types of shade cloth to determine their effect on mean air temperature within HTs. Interestingly, when comparing silver cloth with black cloth, the mean air temperature was higher in HTs with silver shade cloth. In externally mounted shade cloths with the same shade factor, dry nets provide less cooling than wet nets.  

If it gets too hot, expect plants to die. High root zone temperature (RZT) can influence plant growth and function. Increased air temperature and RZT in the unshaded HTs likely increased plant mortality and reduced plant growth, particularly in plants grown with black mulch. 

Shade cloth brings down the temperature inside your high tunnel, but is still hotter in the day than average outdoor temperatures. HTs with shade cloth had similar soil temperature as outdoor soil temperatures, but shade cloth provided reduced soil temperatures during day and night when compared to non-shaded HTs. No air temperature difference was recorded in the night hours between the two types of HTs. During night hours, soil volumetric water content (VWC) was greater in the shaded tunnel than in the non-shaded tunnel. Soil VWC increased in the shaded tunnel between day and night. Shading did not affect average relative humidity (RH) levels during the day or night. However, relative humidity levels were lower outside during the night than in either of the high tunnels.

Insect pressure

Researchers also looked at the relationships between pests, temperature, and shade in high tunnels. They found that in pac choi trials, the major pest problems were whiteflies, thrips, aphids, and Southern armyworms. Though the number of thrips, whiteflies, aphids, leafhoppers, and predatory flies were similar among shade cloth treatments, they found that both black and silver shade cloths harbored more beneficial parasitoids than unshaded conditions in one study season. The high light conditions in the unshaded treatment may have negatively impacted the parasitoid wasps. Temperatures in HTs may not have an impact on insect pressure. Thrips were the only pest that decreased in number with increasing HT air temperatures. Other insect numbers were variable among shade treatments in increasing air temperatures. 

Researchers also found success in attracting beneficial insects by planting Sweet Alyssum, buckwheat, or marigold at the front and back of leafy green beds and corners of each high tunnel. The push-pull system, including companion planting and refuge planting, is worth further research in high tunnel systems.  

Image credit – ICIPE

The ‘push-pull’ strategy,  uses a combination of behavior-modifying stimuli to manipulate the distribution and abundance of insect pests and/or natural enemies. Pests are repelled or deterred away from the main crop (push) by placement of plants that mask the host or are repellent. The pests are simultaneously attracted (pull), using attractive plantings, to other areas such as traps or trap crops where they are concentrated, facilitating their control.

Shade and Light

Shade cloth reduced air temperature, root zone temperature (RZT), and photosynthetic photon flux density (PPFD). Tomato plants in HTs need to receive sufficient PPFD to maximize fruit yields, and under the shade cloth the PPFD was below the requirements for tomato leaf photosynthesis, decreasing the marketable tomato yield. To avoid this reduction in necessary PPFD, researchers recommend that externally mounted shade cloths are removed once high air temperatures are no longer a limiting factor, or when daylengths are short and irradiation is low. 

The plastic films that cover HTs do age, and with age the level of light transmittance can change, depending on the quality and plastic film composition. In this study, the HT plastic without any shade cloth reduced PPFD by 36%. It is recommended that the plastic film is washed to prevent excessive light reduction in your HT. 

Finally, when selecting your shade cloth, remember that the net shade factor provided by the manufacturer is based on the photosynthetically active radiation (PAR) transmissivity rather than the solar transmissivity. 

There is more to explore in these research papers, and I am looking forward to more findings and recommendations on the effects of a combined use of compost, cover crops and fertilization to improve long-term soil fertility while supporting the immediate nutrient availability needs of the current crop; more on effective and economical push-pull systems; and how shade and moisture can help expand our growing season. 

This blog used the following sources: 

Díaz-Pérez, Juan Carlos, Sudeep Bag, Timothy Coolong, Xuelin Luo, Amanda Hodges, Mamata Bashyal, Hayley Milner, Naga Charan Konakalla, and Adam Pitcher. “Plant Growth, Fruit Yield, and Tomato Leaf Curl Disease of High Tunnel Organic Tomato Affected by Shade Net and Plastic Mulch Color”. HortScience 59.3 (2024): 323-331. < https://doi.org/10.21273/HORTSCI17516-23>. Web. 5 Mar. 2024.

Laur S, da Silva ALBR, Díaz-Pérez JC, Coolong T. Impact of Shade and Fogging on High Tunnel Production and Mineral Content of Organically Grown Lettuce, Basil, and Arugula in Georgia. Agriculture. 2021; 11(7):625. https://doi.org/10.3390/agriculture11070625

Tian, Shufang, Jeffrey K. Brecht, Bala Rathinasabapathi, and Xin Zhao. “Influence of Soil and Nutrient Management Practices on Crop Productivity and Quality in High Tunnel Organic Leafy Green Production”. HortScience 58.12 (2023): 1610-1621. < https://doi.org/10.21273/HORTSCI17327-23>. Web. 5 Mar. 2024.

Written by Elizabeth Tobey

You may have heard the term “regenerative” a lot lately in agricultural circles or on food labels at the grocery store. The term has caught the attention of consumers interested in the impact of their food choices, and farmers and policymakers looking for ways to adapt to or mitigate climate change. We are at a unique moment to promote transformative farming practices, but it’s critical to understand what we’re rooting for.

Although the term ‘regenerative’ has gained widespread traction, definitions of the term vary widely. Unfortunately, in some cases, it is used to describe conventional agriculture that adopts a single conservation practice, such as no-till, and labels it regenerative. Changing one practice and calling it regenerative drastically misses the mark of what truly whole-system, regionally-adapted, thoughtfully-practiced organic and regenerative agriculture can be.

Organic farmers have been using regenerative organic practices since long before the terms “organic” or “regenerative” were coined. Yet, as a wave of climate-change awareness sweeps over decision-makers in food and agriculture policy, organic farming is often overlooked as a climate solution. 

Organic agriculture is grounded in principles that collaborate with nature, foster healthy soil, and contribute to clean water, biodiversity, and thriving farm communities; it encompasses the essence of holistic and regenerative farming. At OFRF, we recently embarked on a project to map the synergies between organic and regenerative agriculture practices and develop a messaging toolkit to help organic advocates explain how organic is regenerative. We found three key themes that come together to highlight the critical role that organic agriculture can play in creating a healthy future for people and the planet:

#1 Organic Agriculture Supports a Resilient Planet. It is…

Climate-Friendly:

Nearly 90% of organic farmers use cover crops, which protect soil, help sequester carbon, and prevent erosion. Organic growers also lead the way in crop rotation, intercropping, and green manures, all of which are research-backed methods to improve resilience and increase fertility. 

Healthy for Soils:

Maintaining and improving healthy soil is a core requirement of organic agriculture. The USDA National Organic Program mandates best conservation management practices, including diversified crop rotation, cover cropping, careful nutrient management, and other methods to protect or improve soil health. 

Protective of Biodiversity:

Organic farmers are required to preserve and protect biodiversity and natural resources to replenish or maintain ecological balance on farms. Research has found that organically managed lands have higher rates of both species richness and abundance when compared to conventional cropping systems. Organic farming significantly increases populations of beneficial insects, birds, soil-dwelling organisms, mammals, reptiles, and plants. 

Systems Focused:

Organic production emphasizes overall system health, including clean air, water and soil.  The interaction of management practices is the primary concern, rather than any individual technique. 

#2 Organic Agriculture Builds Healthy Communities. It is…

Good for the Economy:

Organic farms and businesses create jobs throughout the supply chain. In 2022, organic food sales in the United States broke through $60 billion for the first time. And in 2023, total organic sales (including organic non-food products) were a record $67.6 billion, according to the Organic Trade Association’s Organic Industry Survey. The organic sector is expected to remain stable or grow as generations who are conscious about health and the environment prioritize purchasing organic food for their families, especially their children.  

Safer for Farmworkers and Rural Residents:

Organic farms rely on natural inputs, like compost and natural pesticides. Certifiers review all inputs organic farmers plan to use and conduct random tests to ensure no prohibited pesticides are used. These regulations protect farmers, farm workers, neighbors, and nearby waterways from exposure to toxic chemicals. 

Better for People:

Pesticides are designed to be poisons. The properties that make them toxic to insects and weeds can also make them toxic to other forms of life, including people. Eating organic protects people from toxic pesticide and herbicide residue on food products.

Better for Animals:

The use of antibiotics and hormones is prohibited in organic production. Instead, organic producers must use holistic practices to maintain livestock health. Studies show that organic farms harbor fewer antibiotic-resistant microbes than their conventional counterparts, and organic meats are less likely to be contaminated with antibiotic-resistant bacteria than conventional meat products (another health benefit for consumers). 

#3 Organic Agriculture is Trustworthy. It is…

Third-Party Certified:

Organic farming has a legal definition, which makes it a solid tool for holding farmers and food producers accountable to sustainable practices and letting consumers know what they are supporting with their food purchases. To sell products labeled “organic,” farmers and food processors must undergo a rigorous certification process, which includes working with a USDA-accredited third-party certifier which ensures integrity and accountability.

Non-GMO:

Organic is THE choice for consumers wanting to avoid GMOs. Organic certification prohibits farmers from using genetically modified seed and requires practices that prevent contact of organic crops with GMOs.

Tried and True:

Organic farming is not new; many of the methods used in organic farming today have their roots in traditional ecological knowledge and Indigenous farming practices. The National Organic Program was created over 30 years ago, informed by decades of experience of farmers and ranchers, soil and plant scientists, food system workers, environmentalists, and consumers. 

Evolving and Improving:

The standards are designed to be responsive to changing needs and continue to evolve. Organic agriculture may not be perfect, but there are built-in pathways for improvement. 

In short, organic agriculture is a powerful tool to address climate change, build healthy communities, and foster a sustainable future that we can trust in. To achieve this future, we must continue to invest in organic agricultural research, products, and farmers. 

Bringing farmers & researchers together

At OFRF, celebrating and strengthening the relationship between the researcher and the farmer is one of our greatest joys. We see these roles coming together and overlapping at Field Days – educational events often held on a working farm or ranch or at an agricultural research site. These events usually include demonstrations of specific management practices and equipment or highlight research methods and results. They are an excellent way for farmers to learn about new research findings, researchers to gain insight into the most pressing issues for producers, and networks to grow between them to continue these exchanges. 

With our team spread across the country, we are eager to know more about field day events happening in various regions and to highlight more stories of these cross-pollination events. Do you host Field Days? What kind of events do you plan? Who attends them? And best of all – what are you researching? We want to see what you are up to!

Back in November, our Development Director, Leah Lawson, had the opportunity to attend a carrot trial field day at McHenry County College’s Center for Agrarian Learning in Crystal Lake, Illinois, the ancestral homelands of the Peoria, Bodwéwadmi (Potawatomi), Myaamia,  Očhéthi Šakówiŋ,  Hoocąk (Ho-Chunk), and Kiikaapoi (Kickapoo). Here’s what she had to say about the experience:

Carrot Trial Field Day

By Leah Lawson, Partnerships and Development Director OFRF

It was one of those beautiful fall days when the air was crisp and cool. As I drove out to the campus, the sky faded into a beautiful prairie sunset of purples, reds, and oranges – much like the colors of what was to be my favorite carrot of the night.

Our three hosts for the evening, Sheri Doyel, Micaela Colley, and Kim Sowinski, took us through the process and purpose of the project titled “Carrot Improvement for Organic Agriculture” (CIOA). We learned about domestication pathways and how culinary and cultural history blend together to create varieties throughout the world. We also learned about the process of carrot breeding. They only flower after the second year of growth, so harvesting the seeds is a long process. Each carrot variety has to be grown in a separate tent to keep them separate and prevent insects with unwanted pollen from getting into the mix.

Of course, the best part of the evening was tasting the carrots. We tried ten varieties grown on the MCC Student Farm, rating them each for taste, sweetness, texture, and color. Sheri and Kim collected all of this data to aggregate with the results from all the other farms participating in the study. Each variety will also receive ratings from the growers on soil health, disease resistance, and production rate. You can sign up on the Seed Linked website if you want to join a similar trial.

Unfortunately, my two favorite carrots were not great producers, so I don’t think I will find them at my local farmers’ market soon. However, I did get to take some of the leftover carrots. After returning home, I conducted another quick tasting with my kids, and we all marveled at their differences.

OFRF is working on building a database of Field Day opportunities around the country, so if you know of events like this, please get in touch! Let us know how you communicate or find out about research in your area. You can reach us at fieldday@ofrf.org 

If you’re interested in learning how to host a Field Day, check out this Farmer Field Day Toolkit from SARE.

New disease-resistant carrot and tomato varieties being developed in partnership with organic farmers

OFRF just released two new research summaries highlighting this carrot trial and a similar tomato study. These two important, long-term organic crop breeding projects both focus on the interaction between soil microbes, genetics, and disease management, and both involve participatory plant breeding efforts between organic farmers and researchers.

Carrot Improvement for Organic Agriculture (CIOA): Leveraging On-Farm and Below-Ground Networks

Carrots are an economically important crop for organic specialty crop farmers, with 12% of US carrot acreage under organic management bringing more than $120 million in farmgate sales. Since 2011, researchers leading the CIOA project have been looking to improve carrot varieties for organic production. A central idea behind this work is that carrot varieties associate effectively with soil microbes for enhanced resilience to biotic and abiotic stresses, which can reduce the need for off-farm inputs. By conducting on-farm research and participatory carrot breeding projects, scientists and farmers work together to better understand below-ground networks and develop new varieties.

Tomato Organic Management and Improvement Project (TOMI): Part II

A diverse and virulent complex of fungal, watermold, and bacterial pathogens threaten organic tomato production. The Tomato Organic Management and Improvement Project (TOMI): Part II, led by Dr. Lori Hoagland of Purdue University, builds on previous research (TOMI: Part I), which found that soil and root microbiomes play a substantial role in mediating crop disease resistance. In this second phase of TOMI, researchers want to better understand the role of tomato genetics in promoting specific rhizosphere microbes that mitigate disease issues. The three-pronged approach investigates, 1) The potential for microbial biocontrol agents to promote disease suppression, 2) How plant genetics and microbes interact, and 3) The development of varieties with stable disease resistance using a farmer-participatory approach.