Best cultural practices for microgreens: A quantitative and seasonal analysis

Summary

Microgreens production has gained popularity in recent years, but growers face challenges in production such as mold problems and maintaining high yields throughout the year. The goal of this project is to determine the minimum input requirements for high yielding microgreens growth in varying seasonal conditions in the Northeast by determining the microgreens varieties that are seasonally optimal for our greenhouse conditions, as well as determining how much additional heat is required for optimal microgreens growth.

Over the past several months we have been able to determine some of the most important factors leading to successful microgreens production by measuring yields of each tray. 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. Since November, Jamie O’Hern and Allan Gandelman have taken over growth and maintenance of the microgreens enterprise.  Our technical advisor Neil Mattson at Cornell University assisted in the original set up of our experiment as well as with budget-related calculations. He has also become more involved with Allan Gandelman on other projects on the farm.

Objectives/Performance Targets

Each week, 16 trays are filled with soil mix. The soil is moistened, and two each of eight varieties of microgreens are seeded and covered. One of each variety (8 trays) are placed on a heat pad set to approximately 75 degrees F, and the other eight are left unheated. The trays are uncovered once germinated (1-3 days), and then harvested 14-21 days later, depending on the season. We have recorded yield, time to harvest, and the amount of energy used by the heating pads for each treatment since March 2014, and will continue that protocol until the spring of 2015.

We chose our highest yielding tray for each variety in each month to use as a benchmark for determining effectiveness of the variety at certain times of the year. A table has been compiled of those highest yielding trays, resulting in some early observations (see attached pdf). Winter is an especially difficult season to maintain productive microgreens due to a lack of light, daytime heat, and ventilation in the greenhouse, so data will continue to be collected through this winter until springtime.

Besides continuing to share results on the facebook page, an event will be held (in Summer/Fall 2015) to demonstrate the farm’s microgreens set-up and to further share our findings.

Accomplishments/Milestones

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.

The other ongoing task throughout the season has been to adjust our conditions as the temperature, humidity, and amount of sun changes. One important adjustment 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. 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.

At the end of the year spent collecting data, we will be able to determine which varieties perform best in each month in order to provide information to growers so that they can create the most profitable mixes for market. Attached is a spreadsheet containing yields for each variety in each month so far.  Through our continued measuring of yields, we’ve been able to determine .25 lbs/tray as a minimum yield required in order for the tray to cover the costs of soil, trays, labor, and seeds when selling them at an average of $28/lb. We’ve also used the Interactive Greenhouse Crop Budget by  Dr. Robin G. Brumfield from Rutgers NJ Ag Experiment Station to approximate the profitability of microgreens at a 2-week growth cycle (using no heat pads), 2.5-week growth cycle (with some heat), and a 3-week growth cycle (with heat constantly on) to show the change in profitability between summer, spring/fall, and winter time with the information we have collected so far. 

Table 1. Cost per tray

Table 2. Profitability in summer versus winter (via http://aesop.rutgers.edu/~farmmgmt/green-house/greenhouseinteractiveform.html)

Our budget spreadsheet will continue to be developed and by summer made available online and shared with growers who attend our future workshop to use as a tool for planning their own microgreens enterprises.

• Highest yields in each month

Impacts and Contributions/Outcomes

A growing Facebook group was created (https://www.facebook.com/groups/497563250373763/) and currently hosts discussion for 108 members across the country.

Collaborators: