An alternative organic strawberry production system grown vertically in high tunnels

Final Report for OS12-064

Project Type: On-Farm Research
Funds awarded in 2012: $15,000.00
Projected End Date: 12/31/2014
Region: Southern
State: Arkansas
Principal Investigator:
Dr. M. Elena Garcia
University of Arkansas Division of Agriculture
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Project Information

Abstract:

This project was designed to address two issues facing sustainable fruit production in the South:

1) Season extension of strawberries with cultivar selection and management practices.

2) Methods to increase the production area of a high tunnel (HT) by testing strawberry production in an elevated system over in-ground beds.

High tunnels offer protection from frosts and rain resulting in minimal disease pressure and improved fruit quality and quantity.  Additionally, HT extend the cropping season with little or no added heating energy.  HT production is still relatively new technology in the U.S. and many producers struggle to utilize these structures to their full capacity.  One area of optimization exists in improving the use of the vertical space above the growing beds, which is often not used at all.

Strawberries are an ideal crop to investigate the potential of an elevated production system in a HT.  Strawberries are compact, can be managed to produce fruit in the off-season and HT are believed to have a positive effect on yield (Demchack, 2009).  In addition, strawberries can be grown in an elevated, HT system without the high inputs required in a typical commercial system such a sfumigation and plastic.  Also typical of commercial production, the fruit is marketed on a relatively short time frame, from 4 to 6 weeks, in April through May, in Arkansas.  This concentration of production creates a sub-optimal situation where strawberries show up simultaneously in the marketplace, therefore limiting prices and profits.  With cultivar selection and high tunnel management practices, it is possible to extend production into the off-season.

The two primary means of strawberry season adjustment are high tunnels and genotype selection.  Day-neutral strawberry varieties do not require specific day-lengths to initiate flowers and set fruit as long as temperatures allow (Ballington et al., 2008).  Growers in many parts of the United States use day-neutral strawberries to produce high-value fall crops.

The grower-collaborator (Gros, Foundation Farm) of this proposed project toured small sustainable farms in France and learned of their production system.  This system involves growing strawberries, year-round, in an elevated system in high tunnels.  The production system for this project relates to this design.  Gros’s high tunnel is a standard 30’x96′ design with approximately five 4-ft wide beds and four 3-ft wide paths.  A strawberry support system was used over the beds with easy reach from the path.  Wood-frames were constructed over the length of the beds with suspended cradles made of metal tubing/rod.  Two lines side by side will be suspended over the three middle beds for a total of six lines.  “FiltrexxSoxx” soil-tubes were laid inside the metal cradles, and filled with compost.  Strawberries were planted inside the tubes along 2 parallel lines at 1 foot interval, for a total of about 192 plants per tube and roughly 1200 plants in total for the high tunnel.  Soil tubes were equipped with drip irrigation for an even distribution of the water through the tube.  The water was already at the site with enough pressure to satisfy the elevated tubes.

Plants were grown in-ground in the high tunnel as a control production system.  Two day-neutral cultivars ‘Radiance’ and ‘Festival’ were tested using three planting dates: late July, late Aug and late September.  The cultivars ‘Radiance’ and ‘Festival’ were selected because they have performed well in previous high tunnel research at the UA.  Because the best planting dates to maximize season extension are unknown, three planting dates were used (8/22/12, 9/12/12, 10/3/12).  Project plans were to compare results to a similar project underway at the UA.  This project involves growing in-ground, day neutral strawberries under high tunnels, with multiple planting dates and conventional fertilization.

This proposed system addresses both issues stated above facing sustainable fruit production in the South through season extension o fstrawberries and optimizing high tunnel production space.

Introduction

The impetus for this proposal came from a certified organic grower in Northwest Arkansas (Patrice Gros, Foundation Farm, Carroll County, AR). Gros received a HT NRCS EQIP grant and was seeking information on growing strawberries above his in-ground production beds to maximize the space under protected cultivation. After researching this issue, it became clear that this production system has not been fully researched in the U.S., especially in the mid-South region and no other growers in AR were identified growing elevated strawberries in a HT.

An increasing number of producers in the U.S. are expanding their operation with HT structures. HT’s offer protection from frosts and rain, resulting in decreased disease pressure and improved fruit quality and quantity. Additionally, HT extend the cropping season with little or no added heating energy. HT production is still relatively new technology in the U.S. and many producers struggle to utilize these structures to their full capacity. One area of optimization exists in improving the use of the vertical space above the growing beds, which is often not used at all.

The University of Arkansas (UA) began research on off-season, day-neutral, in-ground strawberry production in HT in autumn,

2010. This research demonstrated the feasibility of off-season strawberry production. Fruit was produced from late November until early January when production was shut down (to allow plants to survive deep winter temperatures). Fruit production resumed in April. Information obtained in this study (cultivar selection, planting date, etc.) can be adapted for other production systems such as elevated strawberry production in HT. Research in the SARE database revealed a similar project, SW07-035 “High Value Crop Rotations for Utah Tunnels”, growing strawberries vertically in HT. A significant challenge faced in this study was injury to the strawberry plant roots in the harsh Utah winters (Rowley,

2010). This should be less of an issue in the mild winters of Arkansas, however, protective measures will be taken in the event of damaging cold temperatures.

Strawberries are an ideal crop to investigate the potential of an elevated production system in a HT. Strawberries are compact, can be managed to produce fruit in the off-season and HT are believed to have a positive effect on yield (Demchack, 2009). In addition, strawberries can be grown in an elevated, HT system without the high inputs required in a typical commercial system such as fumigation and plastic. Also typical of commercial production, the fruit is marketed on a relatively short time frame, from 4 to 6 weeks, in April through May, in Arkansas. This concentration of production creates a sub-optimal situation where strawberries show up simultaneously in the marketplace, therefore limiting prices and profits. With cultivar selection and high tunnel management practices, it is possible to extend production into the off-season.

Project Objectives:

Extend the production season of strawberries by managing with cultivar selection and planting dates.  Two day-neutral cultivars, ‘Albion’ and ‘Festival’ were selected because they have performed well on preliminary UA research of off-season high tunnel strawberry production.

Determine the effectiveness of increasing the production area under a high tunnel by comparing strawberry production in an elevated system to in-ground beds, all under a high tunnel.

Cooperators

Click linked name(s) to expand
  • Patrice Gros

Research

Materials and methods:

A randomized complete block design will be established with two high tunnel production systems, elevated and in-ground; two cultivars ‘Radiance’ and ‘Festival’; three planting dates, July, August and September; and three replications. Yield and yield quality will be recorded from each experimental unit beginning approximately six to eight weeks after planting for the first two plantings and then the following spring for all three planting dates. This data will be collected twice weekly until plants cease to produce. Weeks in harvest will be calculated and starting and ending harvest dates will be recorded. Plants will be allowed to produce a second year beginning in the fall of 2013 and the spring of 2014.

Because conventional strawberry plant nutrition is a highly researched area, it is known that potential yield can be assessed with foliar nutritional analysis. Even though this project will be an organic strawberry production system, foliar N content can still serve as indicator of potential yield. The UACES package of 6 analyses will be used for each treatment. Nutritional status of the plants will be monitored with foliar analysis; a service provided to strawberry growers in the state.

Research results and discussion:

This study was not brought to completion due to the fact that the tunnel was destroyed by a tornado in summer 2013.  Some observations were made before the study was destroyed.  Observations showed several problems that would have to have been addressed to improve the set-up of this elevated strawberry planting system.  Significant problems with Botrytis on the strawberries and on the strawberry plants were encountered during the study.  Overall, early indications were that several serious issues would have to be worked through before an effective and sustainable elevated system could be developed.

The following report submitted by the collaborative farmer, Patrice Gros, provides his observations and insights. This report was submitted by Patrice Gros in March 2014:

High tunnels are very efficient at creating a micro climate where crops can grow beyond their normal outdoor time-             frame, and be protected from various outside weather related impacts, as well as from some predators, including insects. In most cases, crops yield and quality are higher leading to higher profitability.   However, high tunnels are expansive to build.

So, one primary objective at our farm is to maximize the use of that prime space created inside the high tunnel. Most high tunnels are used as a 2 dimensional surface, although some crops (tomatoes) can be trellised for some 3 dimensional gains.

In our 30 foot wide high tunnel, the spacing goes: 3 foot bed, 2.5 foot path, 4.5 foot bed, 2.5 foot path, 4,5 foot bed, 2.5 foot path, 4.5 foot bed, 2.5 foot path, 3 foot bed (That’s 29.5 foot, I know). This results in a surface utilization ratio of 65%.

Building a shelves system carrying plants 6 feet up in the air, has increased that ratio to 95%.

SYSTEM DETAILS:

  • Our hoop-house is a standard 30 by 96 design, sold as a kit by Morgan County, Mo. It comes with 6’ bow spacing, 2 3/8 galvanized tubing and 6mil 4 year poly film, 5’ side walls with drop curtains. It was built in the winter of 2011 as part of an NRCS Equip grant.
  • Bed set-up inside is 4 foot wide beds with 3 foot wide paths. The house contains 5 beds and 4 paths in succession as in: bed/path/bed/path/bed/path/bed/path/bed.       Beds already existed and had been cultivated successfully over the last 6 years.
  • Strawberry support system was built over the 3 central beds for easy reach from the paths. Cedar-post frames span over the beds with attached “carrying tracks” supporting the “soil-tubes”. Carrying tracks are made of 1” electrical metal conduit (EMT tubing). It takes 2 lengths of EMT tubing to create a “track” able to carry a tube-line. There is a total of 3 tube-lines per bed, i.e. 9 tube-lines in total, each 90’ long.
  • material is already used for strawberries and other applications in some areas but operators have used it mostly on the ground. Other systems are in place in European countries where extended strawberries seasons are carried out inside high tunnels using suspended shelves with specially formulated soil bags. 
  • Soil tubes will be equipped with drip irrigation (drip tape) laid atop the tubes allowing for an even distribution of the water through the tube. The water is already at the site with enough pressure to satisfy the elevated tubes.

BENEFITS/ISSUES (As of 01/2014):

The gain of space was a genuine as the shelves did not affect the plants below, in term of light access and general ability to grow below the shelves. Access to the plants from a farmer standpoint was adequate. The shelves did not interfere with the work done below them. However, the height of the shelves creates a somewhat impractical situation for the work done on the shelve plants, such as visual check or clean-up, or transplanting. Most of that work required moving small ladders which not always time-efficient and can lead to falls. I recommend setting the shelves at around eye-level, around 5.5 feet, so that some of the work can be done without ladders. 

The use of Filtrexx bags was not optimal. It was labor intensive to fill up and it did not create an optimal place to grow the plants. Advantages included ease of setting up on the shelves, ease of opening holes and transplanting and ease of irrigation set up. One problem was uneven irrigation as water tended to fall straight down from the irrigation tape through the bags. Another problem is the weakening of the bag material, most likely from UV degradation, after only 2 full years. Given the high cost of the Filtrexx material, I recommend looking for alternative soil containers, possibly in plastic or burlap form, especially formulated for the crop type. Those bags would be ready to use and changed as often as needed. 

The drip irrigation was anchored onto the bags with metal staples, which was fine as long as the stapling was done at least on every other bag in the line.

Another major issue proper to the material and the situation was the quick drying of the medium in hot conditions. The watering had to be very carefully monitored and a lapse in that watch would be fatal to some plants.

Maintaining adequate nutrient levels seemed to be a problem from the start. Using an average “garden soil” from the start to fill up the bags needed to be quickly supplemented by liquid nutrients in the form of fish emulsion and other liquid plant supplements. A better solution seems to be the use of replaceable bags formulated to last for a specific time. 

Yet another, more minor issue has been the build up of moss on the north side of the tubes, possibly robbing some of the moisture and nutrients from the plants. Occasionally, weeds have also come through the netting or trough the plant holes. We recommend that the soil mix used be either sterile or at least low in weed seeds.

           Crops Results: Three crops have been used so far inside the tubes:

  • Strawberries: originally, all tubes were planted in strawberries. The position high in the air did not prevent the berries from rot. Also the strawberries were very sensitive to both moisture levels and nutrient levels, with leaves yellowing and plants stunting. Nutrients were added in the form of liquid fish emulsion. In all, the strawberry yields were less than half of those achieved in plain soil at the farm. Harvesting the fruits required the use of ladders and was not particularly made easier by the shelves. Weeds were effectively suppressed by the netting material.

  • Cucumbers: a crop of pickling cucumbers was seeded directly in the bags. The results were satisfactory with plants falling off the tubes and the fruits hanging down, allowing for an easy harvest. The yields were low, reflecting a weakening of the nutrient levels in the bags.

  • Parsley: parsley was by far the best experiment with yields per square foot ($1/squ. foot/month) at the top of the farm crops ranking. Parsley is compact, and seems to tolerate the variation in moisture and nutrient levels.

In general, the results seem to point at a correction of the system where the soil medium is changed on a regular basis (every 2 years). Disposable bags (plastic, burlap) might be sourced that will be easily loaded and unloaded.

Crops with high tolerance to moisture level variations will do better in that environment. More crops need to be experimented with to find a good set of profitable options.

Participation Summary

Project Outcomes

Project outcomes:

A valuable outcome of this project is the knowledge of problems and issues that were evident from the start as discussed in the Results and Discussion/Milestones section of this report.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.