Best cultural practices for microgreens: A quantitative and seasonal analysis

Final Report for FNE14-800

Project Type: Farmer
Funds awarded in 2014: $7,710.00
Projected End Date: 12/31/2015
Region: Northeast
State: New York
Project Leader:
Allan Gandelman
Main Street Farms, LLC
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Project Information

Summary:

The aim of this project was to determine the best varieties of microgreens during each month of the year in central New York State. Growing them in a minimally-heated greenhouse means year-round growing is possible; but is it always profitable? We seeded 8-9 different varieties of microgreens (including Red Russian Kale, Kohlrabi, Scarlet Frills Mustard, Mizuna, Red Cabbage, Garnet Giant, Tatsoi, Southern Giant Mustard, and Amaranth) each week for a year, and weighed the yield obtained from each tray. We proved that this enterprise is profitable in spring, summer, and fall, and that with additional heat, can even be profitable in winter. Mizuna, red russian kale, red cabbage, and kohlrabi offered the most consistent yields even in cooler temperatures. Mustard varieties do especially well in warmer months. With a yield of at least .25 lbs per tray, producers can expect to make a profit of $150-$300 by seeding 40 trays each week. During a farm field day in September 2015, attendees were able to learn about all aspects of growing, washing, packaging, and marketing microgreens successfully.

Introduction:

Microgreens growing is an increasingly popular enterprise both on small diversified farms as well as in people’s homes, as a way to grow high quality greens year-round. Throughout this project we have been able to determine some of the most important factors leading to successful microgreens production by measuring yields of each tray of several common varieties. Liz Burrichter seeded and harvested the microgreens each week while Isaac Arginteanu monitored and maintained the various environmental controls--heating pads, grow tables, ventilation, etc. For the final months of the experiment, starting November 2014, Jamie O’Hern took over growth and maintenance of the microgreens enterprise.  Allan Gandelman, owner of Main Street Farms oversaw all aspects of the operation. Our technical advisor Neil Mattson at Cornell University assisted in the original set-up of our experiment as well as with budget-related calculations.

Our motivation for growing microgreens came from the various market opportunities it provided to Main Street Farms. Microgreens are a unique and high value product that not only had a loyal customer base among restaurant and farmers market customers at the Syracuse Regional Market, but also were able to be grown in otherwise underutilized greenhouse space and over a longer season than other crops. Microgreens not only were a source of revenue during winter and early spring months when there was little else to sell, they also allowed the farm to maintain connections with wholesale accounts and market customers throughout the whole year.

Project Objectives:

The goal of this experiment was to test the efficacy of growing microgreens in a soil-less media in trays using various greenhouse conditions. The experiment followed a randomized complete block design. The three main treatment blocks (germinating/growing environments) were:

  • Germinated and grown on heating pads at 80F
  • Germinated at 80F, grown at ambient greenhouse temperatures
  • Germinated and grown at ambient greenhouse temperatures

Over winter, the second treatment listed above was dropped from the experiment. Besides difficulty using the heating pads at all, moving each tray from a spot on the heating pad to a spot off of the heating pad proved cumbersome and difficult to time, and the benefits difficult to quantify. For those reasons, only two treatments, on and off heating pads, have been considered.

Cooperators

Click linked name(s) to expand
  • Isaac Arginteanu
  • Elizabeth Burrichter
  • Neil Mattson
  • Jamie OHern

Research

Materials and methods:

All treatment blocks were seeded in the same way: 1020 20 row seedling flats were filled with soil mix, pre-moistened, and then seed was evenly sown across the surface of the flat. Flats were covered with a light blocking material for the first two days of growth to aid in germination, and then the cover was removed for the rest of the growth period.

For the purpose of these treatments, “ambient greenhouse temperature” means that the temperature of the trays will fluctuate based on the air temperature of the greenhouse. A

thermostat connected to a soil temperature probe controls the heating pads. The greenhouse that housed the experiment is partially heated, but the air inside can drop below 50F during the winter, especially at night. The soil temperature of the heating pad treatment was intended to be be maintained at a minimum of 80F, however the soil temperature of the unheated treatments will fluctuate based on greenhouse conditions, and during the colder months of the year will drop significantly.

Yields were recorded for 24 trays (3 of each variety), with one tray of each variety on a heat pad, and the other two subject to ambient greenhouse temperatures. After augmenting the treatments after winter, the two treatments became on- or off-heating pads.

The experiment was repeated every week for an entire year. Data collected included:  the time it takes for the microgreens to reach harvest maturity (first set of true leaves) and the weight of harvestable microgreens produced by each tray. In addition, environmental data (air/soil temperature, light, humidity) was recorded by a data logger and correlated with the harvest data.

Research results and discussion:

At first, conditions were difficult to control because of inconsistency in the soil mix we had available. Despite our efforts to control conditions within each treatment, low quality soil mix in June especially lowered all yields during a time when they could have been very high. Our first important observation is that consistent availability of affordable, high quality soil mix is imperative. We now have settled on using GreenTree’s AgBlend from Ithaca, NY which is a peat-light blend with coco, earthworm castings, and organic nutrients like greensand, bone char, sulfate of potash, vegetable protein such as peanut meal, and animal protein such as feather meal. Rapid nitrogen availability is important for high yielding microgreens. The nitrogen in many organic soil mixes is often not immediately available during the short 2 week growing period of microgreens, causing yellowing or low yields. We found bottom watering with our aquaponic water or other hydroponic solutions with more available nitrogen was very helpful.

The heating pads sometimes proved a barrier to success. While they certainly seemed to help boost early growth in the first few days after seeding, the benefit of the heat pads was difficult to quantify. The thermostat that came with the heat pads was unreliable, and the way it inserted it into one of the trays for monitoring did not work well. The knob for adjusting the heat was easily knocked by daily working activities. Often, heat pads would over-heat the microgreens soil trays and young germinated plants would dry out, overriding the benefit of the heating pads.

The other ongoing task throughout the season has been to adjust greenhouse conditions as the temperature, humidity, and amount of sun changes outside. Greenhouse doors are open or shut as humidity fluctuates. No extra lighting was used on the microgreen trays, so amount of the amount of light they received varied greatly.

One important adjustment that we made was the irrigation system. Watering by hand became extremely time-consuming once the greenhouse starting getting very warm all day in May, so we set up a hydroponic table that bottom-waters the trays, speeding up the irrigation process and keeping leaves dry (water on leaves encourages mold growth). Ventilation by fans is another very important component in the winter time when greenhouse doors are closed. Because of the aquaponics system especially, the air is very moist,the high humidity encouraged mold and caused crop failures in many trays. Another ongoing project on the farm this year will help facilitate installation of a biochar furnace in the greenhouse, making the air much dryer and potentially affecting microgreens production over the winter when it is running.

In order to correct for some of the variability in our experiment, including growth media quality, heat pad blunders, changing greenhouse conditions, and human error in growing all of these varieties successfully, we chose our highest recorded yield per tray of each variety in each month of the year. These ‘highest yields’ were used to analyze the success of each variety when grown correctly. Starting at the end of November, greenhouse ambient temperatures did not rise above 60F until March. This represents the time period when the colder hardy varieties play a larger role in the microgreens mix..

Our greatest takeaway from this experiment is that microgreens growing can be profitable in 3 seasons with minimal investment. Winter growing is certainly possible, but may require investment in more sophisticated infrastructure (such as heating pads), limiting the mix to only cold-hardy varieties, and the maintenance of reliable markets. In certain years and latitudes more sophisticated greenhouse structures and even supplemental lighting may be necessary to make microgreens a true four-season crop.

The following tables are a breakdown of fixed costs per tray and a summary of our greenhouse air temperature, crop yields, harvest periods, and profitability on a per tray basis. More detail regarding these numbers can be found in the attached data sheet (Microgreens Financial Data Summary) that goes into further detail with this information regarding each variety we tested.

 

# of Trays

40

             

Labor

 

Soil

 

Seed

 

Plastic Trays

   

$/hr

15

$/yd

180

$/lb

40

$/Tray

0.5

 

Labor Hours

6

trays/yd

240

lbs/tray

0.007

Uses/Tray

10

Fixed Cost/Tray

 

$2.25/tray

 

$0.02

 

$0.01

 

$0.05

$2.33

 

Summary

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

Temp F

45

45

60

62

65

72

75

75

70

63

57

49

Yield/Tray (lbs)

0.19

0.40

0.42

0.53

0.30

0.32

0.50

0.40

0.36

0.19

0.26

0.29

Days To Harvest

32.00

15.00

14.78

13.78

14.11

13.67

14.00

14.00

17.00

16.63

23.00

25.50

Profit/Tray

$0.29

$5.14

$6.13

$8.33

$3.76

$4.05

$7.79

$5.82

$5.01

$2.25

$4.05

$7.44

Profit/40 Trays

$11.52

$205.78

$245.23

$333.13

$150.27

$161.83

$311.80

$232.77

$200.45

$89.99

$162.19

$297.43

 

We’ve determined .25 lbs/tray as a yield target indicative of an effective growing system. Higher yields are certainly possible and desired, although excessive weights per tray may indicate greens that are closer to “baby” than to “micro”. Below .25lb/tray micros are still profitable according to our model, however lower yields than this can indicate some issue in the growing environment or quality issue with the greens that should be corrected. Our profitability model is also based upon successful growing. Microgreens can be quite profitable if the grown consistently, however crop failures can happen easily as the seedlings are very delicate and prone to mold and drying out. Low yields in May, noted in the above table, were most likely due to inadequate irrigation--difficult to maintain during constant suny conditions. Successive crop failures can make what might seem profitable a money losing venture. On the bright side, because of the rapid cycle time compared to other crops, the grower can learn quickly and experiment and refine and improve their growing system and technique quickly over the course of a season.

Although some crop failures hindered our microgreens operation in our first year during this experiment, the process allowed us to refine our system, and now our yields are more consistent and the farm is successfully growing and marketing 15-20lbs of microgreens a week through retail and wholesale outlets at $28/lb on average. This is mainly through the Syracuse Regional Farmers Market and to restaurant and small supermarket customers in Central NY.

Our profitability model of microgreens represents an enterprise that uses existing greenhouse or high tunnel space on the farm that is unfilled or under-utilized during certain times of the year. We found that in terms of operating expenses, a tray of microgreens, if yields are fairly consistent, and marketing channels are stable, will provide a good return during the main season, and with the right varieties, break-even in the colder months. Our model does not represent an enterprise that takes into account the capital expenses of a dedicated greenhouse for microgreens. Microgreens can justify such an investment for growers wishing to scale up production; but those costs would likely lead to a smaller profit margin than what is indicated in our model.

 

Variety selection:

Varieties should be chosen and grown based either on their high yielding quality, for their distinguishable taste (like a spicy mustard), or for the aesthetic value they add to the harvested microgreens mix (like amaranth).

Mizuna, red russian kale, red cabbage, and kohlrabi offered the most consistent yields even in cooler temperatures. Under proper management these varieties seem to have the potential to consistently yield a quarter pound per tray throughout most of the year with some supplemental heat in winter. These varieties are recommended to form the core of a microgreens mix and have the most potential for being a viable four-season crop. Three of these four, Red Russian Kale, Red Cabbage, and Kohlrabi, did not fare as well in June and can be replaced with warm season mustard varieties.

Mustard varieties (Scarlet Frills, Garnet Giant, Southern Giant) are effective during warmer months, but not recommended for cooler season or winter growing. These varieties can be high yielding in warmer months but were not consistent in cooler months in our system. They however add a delicious spicy flavor and are visually appealing. Some season extension is possible but pushing them through the winter is not recommended based on our experiment. They were a welcome addition to the mix during the main growing season from March - October due to their unique flavors.

Amaranth had an even shorter season, March-September. Deep magenta coloring and unique leaf shape made it an important accent to the mix, but it has the most expensive seeds and was not consistent when average Greenhouse temperatures dropped below 65F-70F. It is not recommended for growing from October through February.

Our trays growing without any supplemental heat ceased to be effective when greenhouse air temperature consistently dropped below 60F, mid Nov-February. When it is too cold, harvests either failed or took 3-4 weeks. While profitability is lower, winter growing can still be viable if charging a winter premium at market, sales are still consistent, or maintaining market connections is very important.

Starting at the end of November, greenhouse ambient temperatures did not rise above 60F until March. This represents the time period when only cold hardy varieties should be grown.

Research conclusions:

One other farmer that we know of began a microgreens enterprise during the time of this grant, and had several conversations with Allan about getting started.  At our educational event several other farmers said they would start growing microgreens in the spring once we gave them the financials and instructions for the process.  

We sought out Neil Mattson from Cornell University as an advisor for this project. After working with us, Neil made Main Street Farms a collaborator on another project concerning heating high tunnels with a biochar furnace, and then using the by-product as a soil amendment. This project is ongoing.

Participation Summary

Education & Outreach Activities and Participation Summary

Participation Summary:

Education/outreach description:

A growing Facebook group was created called Microgreens; (https://www.facebook.com/groups/497563250373763/) and currently hosts discussion for 656 members from all over the world. Active members on the group include both home growers for personal consumptions as well as those starting small businesses. Users post questions and pictures daily on the site, looking for and receiving advice on how to troubleshoot problems relating to the growing medium, watering schedules, mold problems, seed and supply sourcing, and infrastructure. As Admins of the group, we occasionally post new pictures of our set up, or pose questions for discussion.


In September of 2015 we partnered with Groundswell Center for Local Food and Farming to host an on farm high tunnel workshop with the focus of growing microgreens.  The event was only open to farmers who were currently using or building high tunnels.  18 participants showed up to the workshop which lasted for 2 hours.  During this time we gave a hands on training to all the participants that involved filling trays, seeding trays, watering trays, washing, packaging, and then everyone had a chance to harvest a tray of microgreens using methods that we trialed over the course of the year.  After the hands on portion of the workshop we went over seed sourcing, variety selection, and our financial data from the project.  Several of the farmers in attendance said they were going to experiment growing microgreens for their retail and wholesale customers.  

Project Outcomes

Assessment of Project Approach and Areas of Further Study:

Potential Contributions

This technique for growing microgreens in high tunnels certainly is worthy of more inquiry and farmer adoption. Whether or not to grow them over winter is a common question, and our results shine light on this topic. Our experiment shows that in terms of operating expenses a microgreens operation can be break-even or even slightly profitable during winter-months. And this can be especially worthwhile if it supports maintaining or increasing marketing opportunities for main season crops.

Future Recommendations

We answered most of the question that was set out to study, but not all of them. More reliable yield numbers could be recorded during winter months, when success is most variable. The addition of supplemental light over winter could also be studied. This would allow for a higher quality (i.e. bright colors) and more diverse mix during cold months of the year.

One potential avenue of further exploration for seasonal potential of microgreens varieties has to do with the Brassica species of the varieties. The cool season varieties of our selection were B. oleracea and B. rapa and the warm season mustards were B. juncea. Of course there are many different varieties available within these species, and we do not have enough data to generalize across those species as a whole, but it is a point worth noting for those who wish to do more experimentation and exploration of different microgreen varieties.

Microgreens have become an even larger part of Main Street Farm’s business since applying for this grant. Even though success was achieved growing microgreens in trays containing soilless media, the operation at the farm was migrated to occupy our aquaponics system. This method requires less labor time and yields an even greater harvest, possibly due to the aquaponic water’s high temperature and high nitrogen content.

While all kinds of greenhouse operations could benefit from this information about growing microgreens, it is most appropriate for small farms that are looking to supplement the range of crops that they can grow in high tunnels.

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.