Extending the Market Season with High Tunnel Technology for Organic Fruit Production

Extending the Market Season with High Tunnel Technology for Organic Fruit Production

Summary

A series of two primary studies using high tunnel technologies, and modifications to tunnels were conducted to determine how the technologies may fit into sustainable and organic fruit production systems in the south.  The two studies were using high tunnels (HT) for 1) advancing summer ripening blackberries, and 2) extending the harvest season of autumn ripening blackberries and raspberries.  Preliminary studies have indicated the potential for both.  Tunnels were modified to include A) low-tunnels within tunnels (tunnel-in-tunnel) around the fruiting plants, B) covering plants with 30% shade to reduce heat and light load to delay flowering and fruiting and improve fruiting, and C) to screen the tunnels to exclude deleterious insect pests.  The goal is to develop a tunnel production system that would compliment a field production system by extending the harvest seasons, expanding cropping, and improving fruit quality, and would be especially adaptable to sustainable and organic production systems.  

In the second year of the study, data indicate that high tunnels have the opportunity to increase overall harvest and improve marketable yield.  Spring deployed high tunnels may advance the harvest approximately 2 weeks and tunnel-in-tunnel systems can advance the crop an additional 10 to 14 days.  The high tunnels can minimize crop loss due to frosts if supplemental heat is added to the tunnel. Tunnels-in-tunnels are able to provide additional protection from frost damage through increased solar heating and longer heat retention.  A problem with autumn-bearing primocane blackberries and raspberries grown in the South is flowering and fruiting in the heat of the summer season (July and August) resulting in poor cropping and fruit quality.  It was hypothesized, based on preliminary observations and other production systems, that shading may delay flowering and fruiting and avoid peak temperatures during the summer.  However, in the first year only minimal changes in flowering and fruiting were observed.  Because of large variation and small plot size, the effects require an additional year(s) of study.   Screening the high tunnel to exclude deleterious insect pests proved to be an effective pest prevention strategy, especially when combined with trapping and applications of pesticides. The population of spotted-wing drosophila observed inside screened areas of the high tunnel was negligible, indicating that insect screen can be an effective means of exclusion.

As there is significant annual variation meteorologically, environmentally, and with plant performance, results will be corroborated with additional, following years of this study.  

Objectives/Performance Targets

The purpose of this project is to extend the sustainable production of summer berries using HT technology to achieve earlier spring harvest of blueberries and blackberries, and to allow for an extended autumn production of new primocane blackberries and raspberries. The goal of the project is to develop an environmentally and economically sustainable organic fruit production systems combining HT production with traditional FD production and providing for further expansion of organic crop production in the southern region. 

The specific project objectives were:

1. To develop High Tunnel (HT) production systems for season extension of organic high value fruit crops for the southern region.
2. To develop and test pest management strategies for organic HT crop production systems adapted to the southern region.
3. To estimate economic models and to create decision support tools that help producers to manage production systems for profitability considerations
4. To extend the knowledge acquired through the production, pest management, and economic analyses into a multi-dimensional educational, outreach, and extension program.

Accomplishments/Milestones

The 2013 production season was the first year of full production of the two studies and various experiments within this project.  Each study is presented separately.

Study 1.  Advancing cropping of summer floricane blackberries with High Tunnels (HT) and Tunnel-in-Tunnel (TNT) employment.

Blackberries in the HT produced significantly more total fruit and marketable yield, with peak harvest approximately two weeks earlier, than similar plants under field conditions.  Fruit were approximately 10% larger but had lower soluble solids.  Yields in the TNT were lower than in the HT due to insufficient pollination under the TNT, although the percentage of marketable yield was similar to HT and higher than in the field.  Peak harvest in the TNT was approximately 1 week earlier than the HT.  Data indicate that the TNT results in increased daytime and nighttime temperatures, greater nighttime heat conservation, and some additional advancement of crop development and bloom. 

Problems encountered in the HT and TNT continue to be frost control and pollination.  Additional work and experimentation will continue in 2014 and 2015 to maximize heat accumulation and retention in HT and TNT during early bloom and frost circumstances.  Additional pollination with domesticated, boxed bumble bees will be used in future iterations of the study.

Study 2.  Extending the harvest season of autumn primocane blackberries with HT, TNT, and shade treatments.

Primocane blackberries in the HT produced approximately 50% more total fruit and 67% more marketable yield than blackberries in the field.  Harvest in the HT continued approximately 3 weeks after field crop was lost due to October frosts.  The yield of plants in the TNT was similar to those of the HT and 48% greater than in the field.  Harvest in the TNT continued approximately 2 weeks after harvest in the HT when fruit were lost to frost.  Frost protection was significantly greater in the TNT than in the HT.  The percentage of marketable fruit was greatest in the TNT and significantly better than field produced fruit.  

Autumn primocane raspberries produced 38% more total fruit in the HT than in the field with a significantly high percentage of marketable fruit.   Raspberry cultivars varied in performance but there were no cultivar by treatment (HT and field) interactions. ‘Autumn Bliss’ had the greatest yield, ‘Josephine’ had the greatest percentage of marketable fruit, while ‘Nantahala’ had the lowest yields, medium size fruit, but highest fruit soluble solids content.   Shading to reduce heat load on raspberries did not significantly affect cropping, marketable yield, berry size, or soluble solids content.  However, raspberries produced under 30% shade increased yield by 38% across both the HT and field treatments.  Using TNT for autumn raspberries had no effect on cropping compared to the HT alone.  Shade had only a small, marginal effect on delay in flowering for primocane blackberries and raspberries. 

Spotted wing drosophila (SWD) was first observed in 2011 in Arkansas and developed into more of a problem in 2012 and 2013.  In 2013, a portion of the HT was screened to exclude SWD from the production system.  While fruit in the field for fall blackberries and raspberries ranged from 80-100% berry infestation with organic pesticides being applied, the use of screening, trapping within the screened area, and use of organic pesticides reduced SWD damage to the 7-10% range within the screened HT. 

The challenge for fall produced organic primocane blackberries will be SWD control, delaying bloom, providing adequate pollination in the HT and TNT, and protecting against early frosts during an extended harvest season.   Additionally, preliminary indications are that screening HT to protect against SWD may result in excessive daytime heat accumulation.  

Impacts and Contributions/Outcomes

The first year of major harvest of both summer floricane blackberries and autumn primocane blackberries and raspberries continue to support the assertion that HT may be used to advance the harvest in the spring (by approximately 2 weeks), extend the harvest in the autumn (by 2-4 weeks), and result in greater total harvests and marketable yields.  In 2013, the greatest loss of summer crop was due to rain and pests which were both mitigated within the HT.  The preliminary evidence is that TNT technologies are very useful in both increasing HT temperatures during cold periods, and retaining night time temperatures.  Adding supplemental heat was most successful under the TNT compared to the HT alone.  However, pollination within the TNT has been a problem and will be better evaluated in future studies.  Developing a TNT that can be opened partially to allow bee flight, and/or introducing bees directly under the TNT are planned solutions.  The preliminary evidence that shading may delay flowering and fruiting in primocane blackberries and may be useful to raspberry production in HT is encouraging and warrants additional study.  Screening to exclude SWD within a HT combined with trapping appears to be effective means of control. This is especially relevant for organic berry production where the efficacy of materials available to control SWD are limited. We achieved insufficient control of SWD in the field using organic pesticides (a rotation of Entrust and Pyganic).

Although this is the mid-point of the study and data are in early stages, the information from these studies can guide growers in decision making and provide tools for implementation of high tunnel systems for organic berry production.

The data developed from these studies is being used in the development of our economic decision tool for growers.  As the tool is being modified with more experience, it is also giving the research team the opportunity to assess the economic basis for treatments such as TNT, shading, and screening.  Those economic analyses have not been conducted as of this date as the model is being revised.  

Information from this study is being presented at local, regional, and national grower workshops/conferences, and at national scientific and extension meetings.  Information gained in the study is contributing to the development of a Sustainable Blackberry and Raspberry Self-Assessment Workbook for growers.  

• Natchez canes
• Shade structures
• Tunnel in Tunnel structure
• fall berry fd
• HT blackberries
• insect screen
• raspberry harvest
• spring berry fd
• spring berry ht
• fall berry ht inside
• fall berry ht

Collaborators: