Evaluating soil media for vertical hydroponic strawberry production

Final report for FNC20-1222

Project Type: Farmer/Rancher
Funds awarded in 2020: $6,521.00
Projected End Date: 01/31/2022
Grant Recipient: Roscommon Berry Farm
Region: North Central
State: Iowa
Project Coordinator:
Joseph Hannan
Roscommon Berry Farm
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Project Information

Description of operation:

Roscommon Berry farm grows hydroponic strawberries in vertical towers. We are set up for about 16,000 strawberry plants. The farm started in 2019 and is managed by my wife and I. We also grow raspberries and a few vegetables in high tunnels. We have used sustainable practices both on this farm and previous places we have farmed. Practices include using integrated pest management strategies, cover cropping, conservation planting, and insect barrier netting.

Summary:

Vertical hydroponic production is a novel method of producing day neutral strawberries that increases productivity and allows workers to harvest fruit without bending over.  Unfortunately, coir peat + perlite, the media commonly used in this system, does not dry out uniformly.  Farmers end up over or under watering the pots causing nutrient deficiencies (iron and boron) that greatly reduce yield and fruit quality.  Coir peat also comes in hard, dry bricks that must be rehydrated and broken apart before it can be put into pots for planting, which is a very labor-intensive process.  Our project will evaluate three different types of media for ease of filling pots (reduced labor), uniformity of moisture management (better quality), earliness, and total yield (increased income).  Each of these media are partially or completely sourced from renewable sources unlike many types of media used in hydroponic systems.  Our goals are to increase profitability by reducing input labor, identify simpler methods to grow strawberries, make it easier to harvest strawberries, deliver a premium product to market, and demonstrate our methods to other farmers. 

Project Objectives:
  1. Evaluate three different types of media mixes for strawberries grown in vertical hydroponic towers.
  2. Identify the pros and cons of each type of media mix.
  3. Share results with other farmers through a field day, social media, and at the Iowa Specialty Crops Conference.

Research

Materials and methods:

We will grow day neutral strawberries, cultivar Albion, in vertical hydroponic towers and compare the traditionally recommended mix for hydroponic strawberries (coir peat + perlite or 100% coir peat) with alternative mixes as outlined below.  Each mix type will be replicated three times via strip plot.  Plots are 20 towers each (each tower holds 5 stacked pots, 4 plants per pot, for a total of 20 plants per tower or 400 plants per plot).  Strip plots are required for this project as each media type will have different water use requirements and the irrigation system would be unmanageable using a randomized complete block design.  Cultivar Albion was selected since it is the primary cultivar we grow and commonly grown in hydroponic systems.

Towers are fertigated via a single emitter at the top pot.  Each mix will receive the same fertility concentration applied during irrigation cycles.  Fertility concentration will be set at the low recommended range (0.8 to 0.9 EC) adjusted for crop growth stage, using base water of 400 ppm with pH adjusted to 5.8-6.0.

The following mixes will be used:

  • Coir peat + perlite (control)
  • Coir peat + coir chips
  • Berger BM7 Bark pre-mix
    • Update.  This product did not do well during winter testing.  So, we updated the product using a homemade coir fiber + high concentration coir peat mix.
    • We attempted to substitute this product with a homemade mix of corn stover and peat.
  • Coir fiber + coir peat pre-mix
    • Update.  This product is no longer commercially available.  So, we created our own by grinding coir chips using a Predator 6.5 hp chipper shredder. 

Plants will be managed according to industry best practices.  Flowers will be removed until 5 true leaves are present.  Runners will be removed as needed throughout the season.  Insects and diseases will be managed according to best IPM practices as found in the Midwest Fruit Pest Management Guide.  Damaged leaves, small fruit, and old flower stems will be removed as needed.

Fruit will be harvested at red ripe maturity with number ones field packed into clamshells.  Seconds will be bulk boxed.

We will collect data as found in the activity log.

Strawberry Towers
Strawberry towers using plastic clover-shape containers.
Research results and discussion:

Research results are described in our Small Farm Sustainability Podcast and YouTube Final Project Report video.

shared March 2021.

https://www.youtube.com/watch?v=frH4pNBQujQ&t

Plots were established in strips with 3 replications per treatment.  A randomized complete block was not feasible due to the complexity of the irrigation system.

We recorded material cost and planting labor to determine installation cost of each media by tracking labor and material usage.  We used a labor cost of $15 per hour. 

Labor Cost per row (60 towers)

Treatment

Mix

Fill

Plant

Total (hrs)

chips+peat

6

2

3

11

ground chips+peat

7

2

3

12

peat+perlite

8.5

2

2

12.5

ground chips and fiber

4

2

2

8

 

Material Cost per Tower

Treatment

Cost per tower

chips+peat

$4.48

ground chips+peat

$4.58

peat+perlite

$2.72

ground chips and fiber

$4.67

 

Total Establishment cost per tower

Treatment

Material

Labor

Total

chips+peat

$4.48

$2.75

$7.23

ground chips+peat

$4.58

$3.00

$7.58

peat+perlite

$2.72

$3.13

$5.85

ground chips and fiber

$4.67

$2.00

$6.67

 

Mid-April through mid-May was very wet and we lost a large percentage of our plant population. We estimated plant death per tower. Plants that showed any sign of being alive were considered alive.  We counted in June and then again in August after we used runners to fill out the missing holes.  What we didn’t measure was vigor and I think we would have seen some differences if we had. Some planting media had more healthy, vigorous plants in the June measurement than others.  In the August measurement, most plants were healthy and productive.  In June, all media had an average of 3 plants per tower dead.  In August, all media had 1 plant per tower dead.

 

We measured yield for just a week as we were trying to normalize plants after being beaten up from the wet spring.  However, then the Iowa Derecho came and destroyed plants on August 10th followed by our well going dry after 17 weeks with essentially no rain.  Marketable product was packed into pint containers for sale.  Number of pints per plot were recorded.  Pints weigh about 0.6 pounds.  Seconds were placed into bowls and weighed by plot.  Some judgement was used when sizing seconds.  We don’t sell smalls as #1 product.  Other reasons for #2 grading included insect damage, disease, wind damage, and nutrient deficiency. Insect, wind, and disease damage were uniform across treatments. Ground chips and fiber had quite a bit of nutrient deficiency due to the difficulty of maintaining water in the pots and difficulty keeping them hydrated due to poor lateral water distribution. 

Yield

Treatment

#1 pints

Seconds (lbs)

chips+peat

35

10.19

ground chips+peat

42.75

7.56

peat+perlite

53.5

10.25

ground chips and fiber

36.5

5.03

 

 

Participation Summary
2 Farmers participating in research

Educational & Outreach Activities

7 Consultations
1 Online trainings
1 Webinars / talks / presentations
1 Workshop field days
3 Facebook live video events highlighting the project process through the season. 2,304 video engagements.

Participation Summary

5500 Farmers
1 Ag professionals participated
Education/outreach description:

We presented our project progress during the season through use of Facebook live events.  We had 2,304 engagements with each of the videos.  We shared additional information as the season went on via photo posts.  In June, we recorded a video field day in partnership with the Iowa SARE team.  It has been viewed 4,100 times.  This winter we shared results via podcast on the Small Farm Sustainability podcast as well as recording a video that was posted on YouTube.  The Small Farm Sustainability podcast typically has about 800+ listeners per episode.  The results video was just posted with just 18 views in the first few days.  In addition, we had conversations with farmers from around the world.  Of note, we meet virtually with a farmer in MO who is considering strawberry towers as well as a farmer in Russia who is in the process of building out a similar system as ours.

Strawberry Soil Media

https://www.facebook.com/RoscommonBerry

Small Farm Sustainability Podcast feature, March 2021

Exploring Strawberry Growing Media with Roscommon Farm

Evaluating soil media for vertical hydroponic strawberry production – You Tube Video February 2021

Learning Outcomes

2 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Lessons Learned:

Merrilee and I learned a great deal from this project.  See the Small Farm Sustainability project podcast or our YouTube final project report video.  Each media selected in the trial, and several not included, had pros and cons but a couple stood out from the rest.

  • The coir peat and perlite media is still the gold standard for vertical hydroponic strawberry production.  It produced well and good to excellent water distribution vertically and laterally throughout the towers.  It is laborious to mix and prepare but the material cost of the perlite is so cheap that it makes it very cost effective as a media compared to the other options.  Two major negatives to this media is that perlite is not something I want in my compost pile at the end of the season and the media blows away quickly once it dries out.  This is a huge challenge the first few weeks after planting.
  • The ground coir chips and fiber had been our go-to media in in 2018 and 2019.  It is very well drained and plants traditionally did very well for us in that media.  However, 2018 and 2019 were wet years.  2020 was extremely dry and thus plants suffered tremendously.  We were not able to get good lateral movement with this media.  This media should not be used in a greenhouse or high tunnel.  However, it was very easy to prepare.  In fact the easiest of all of the media.  We also found we could create this media cheaper than we could purchase by running chips and fiber through a wood chipper.  This media does not blow away after planting.
  • The coir peat plus chips and fiber at a 1:3 performed well.  It was fairly easy to prepare, handle, and plant into.  It can be handled with equipment so labor could be reduced.  Water distribution vertically and laterally was good but not quite as good as the coir peat and perlite.  It will dry out and blow away but not nearly as bad as the peat and perlite.  We used 1 block coir peat to 3 blocks of chips and fiber.  While this ratio worked in test trials in 2019, the coir peat used in 2019 was a finer grain than what we used for this trial  We believe a mix of 1 to 1 would have resulted in superior water movement and plant production.  In August we set up a small trial in our high tunnel to compare this 1 to 1 mix with coir peat and perlite and the 1 to 1 mix was vastly outperforming the coir peat and perlite in water distribution and plant growth.  So, the proper ratio appears to vary a bit depending on your coir peat grain size.
  • The final media was the coir peat plus chips and fiber at a 1:3 mix but run through the wood chipper. This material was too poorly drained and provided no benefit over the non chipped version. 
  • We had hoped to use a combination of coir peat with ground corn stalks.  However, we did not have the appropriate tools to grind the corn stalks.  Corn stalks can be used as a hydroponic growing media but they do require extra nitrogen to be applied to the crop.  However, they are so cheap that even a little extra nitrogen would not greatly increase the cost.

Moving forward coir peat and perlite will continue to be in the planting mix.  We will also use the coir peat and chips and fiber mix but at a 1 to 1 ratio.  We were hoping to definitively determine what media to use in our strawberry towers and we certainly know which ones we will use again.

The challenges to implementing this project were largely learning how to prepare and handle the media for planting as well as each of the media types have little quirks while minimizing the impact on your crop yield.  Switching to a different growing media requires you to quickly learn how to manage it and then managing many different types of media in one planting required a lot of extra attention. 

Based on what we learned in this trial, coir peat and perlite are still the gold standard for vertical strawberry production.  However, a 1 to 1 mix of coir peat plus chips and fiber could be an excellent alternative for a media that can be fully composted at the end of the season.  The cost of the coir peat plus chips and fiber may inhibit wide adoption.

Project Outcomes

2 Farmers changed or adopted a practice
Success stories:

We were hoping we would reach an audience outside of Iowa due to the nature of the project being quite unique.  However, it was still interesting to have a farm from Missouri and a farm in Russia reach out to us for more information.  Talking to someone across the world who is doing the same thing as you and learning from our project went beyond expectations. 

Recommendations:

The coir peat plus chips and fiber is expensive.  While fully biodegradable and could be excellent applied to fields after the season, the cost likely will deter adoption.  After really looking at the cost of the media, we really think ground corn stalks should be evaluated.  The corn stalk bales we purchased with intent to use as a media for this project were 1/3 the cost of perlite.  Depending on the actual mix ration of coir peat to ground corn stalks, the cost could be less than coir peat and perlite, be fully biodegradable, and partially locally sourced.  However, determining the best mix ration for this media could be a whole project itself.

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.