by Thomas Moore, CFSA’s NC Food Systems Coordinator

cooler 

As the growing season comes to an end it is important for farmers to develop strategies that ensure sales for twelve months a year.  Even though North and South Carolina have long growing seasons, produce farmers who do not use season extending production methods will have a four-month production gap. In order to bridge this production gap and provide product to your customers year-round, proper storage practices are essential. By properly preparing your produce for storage and providing ideal storage conditions, farmers are able to store their products from one to twelve months, depending on the product.

 

Storage Requirements

When storing produce there are four important factors to consider: temperature; humidity; ventilation; and exposure to light. In the book, Sustainable Market Farming, Pam Dawling groups these storage requirements into five different groups based on the needs of particular produce. It is important to note that some crops produce higher amounts of ethylene gas while in storage. These crops include apples, cantaloupes, and ripening tomatoes. Some crops are very sensitive to ethylene gas and will deteriorate if exposed to high levels of the gas. Potatoes will sprout, carrots will become bitter, and fruit will over ripen. In contrast, greens won’t deteriorate when exposed to high levels of ethylene. Take this into consideration when storing various crops within close proximity to each other.

 

Below is a chart that lays out the five different sets of storage requirements:

Condition

Temp. Range (°F)

% Humidity

Crops

Cold and Very Moist

32-40

90-95

  • Roots
  • Greens
  • Leeks
Cold and Moist

32-40

80-90

  • Fruits
  • Greens
Cool and Moist

40-50

85-90

  • Potatoes
Cool and Dry

32-50

60-70

  • Garlic
  • Onions
Warm and Dry

50-60

60-70

  • Sweet Potatoes
  • Winter Squash

 

Preparation for Storage

Proper storage preparation begins with fundamental harvesting techniques. If possible, harvest your root crop produce when the soil is relatively dry.  Also, it is important to trim the leafy tops from your root crops to a short stem to prevent molding during storage. Produce that is damaged or of poor quality will not store well because it is more susceptible to disease and rot. Storing produce that is damaged or of poor quality will most likely affect all of the other stored produce within its vicinity, which could ultimately result in a total loss of product. For long-term storage, overly ripe produce will not store well.  Keep this in mind as you begin to harvest your crops.

 

In preparing produce for storage, think of the three C’s: Culling, Cleaning, and Curing. This essentially outlines the process for preparing produce for storage. First, cull all produce that appears damaged or of poor quality. It is important to continuously monitor your produce throughout the storage process and discard any produce that appears substandard. Next, properly clean your produce before you store it or in some cases before it begins the curing process. Produce that needs to cure should not be washed prior to the curing process. It is recommended to remove all excess soil with a dry brush. The final step before storage is curing.

 

Curing

Potatoes (regular and sweet), winter squash, onions, garlic, and peanuts all require some sort of curing process before they can be placed in long-term storage. During the curing process, the skin of the produce will harden and the starches will convert into sugars. At the end of the curing process you should be able to firmly push the outside skin of the produce without puncturing it.

 

Below is a chart outlining the specific curing conditions for the specific crops:

Crop

Temp. Range (°F)

% Humidity

Duration

(days)

Notes

Onions

85-90

70%

14-21

Well ventilated space
Garlic

85-90

70%

14-21

Well ventilated space
Shallots

85-90

70%

14-21

Well ventilated space
Potatoes

60-75

95%

14

Dark space
Sweet Potatoes

85-90

80%-95%

10

Winter Squash

80-85

75%-80%

5-10

Well-lit space with good airflow
Pie Pumpkins

80-85

75%-80%

5-10

Well-lit space with good airflow
Peanuts

70

40%-50%

14-21

Needs good airflow

 

Ways to Store Your Produce Without Refrigeration

A Coolbot at work Photo by http://berndtsplants.blogspot.com/

A Coolbot at work
Photo by http://berndtsplants.blogspot.com/

Produce can be stored in-ground and covered by some form of insulation (straw, wood chips, dry leaves) once the ground temperature drops to around 35°F.  Additional protection such as a low tunnel or a hooped row-cover can further protect the crop from less than ideal conditions while being stored in-ground. Other outdoor storage techniques are clamping, pit storage and trench storage.

 

For long-term storage it is ideal to store produce indoors. Find an underutilized room or building at your farm and transform it into a cold storage facility. This is possible without the use of refrigeration by using a CoolBot. This device allows you to run a standard window air condition unit at a much lower temperature.  As long as the room is well insulated, the CoolBot will be able to cool the room to the necessary temperature needed for long-term storage. All produce containers will need to be placed on pallets (preferably plastic) or shelving and not on the floor. The other materials that you will need include a thermometer, hygrometer, humidifier, fan, containers that allow for ventilation, and pallets/shelving.

 

As a reminder, CFSA has teamed up with the NC Growing Together project to develop an On-Farm Infrastructure Toolkit to provide small-scale, limited-resource fruit and vegetable producers with the information they need to build scale appropriate post-harvest handling facilities. This toolkit will include chapters on postharvest cooling and washing, curing, cold storage, and funding. The complete toolkit will be released in March

 

Additional Resources:

Growing for Market: Extending the Selling Season with Storage Crops: http://www.growingformarket.com/articles/Extend-the-Selling-Season-with-Storage-Crops

 

Sustainable Market Farming:

http://www.sustainablemarketfarming.com/

 

CoolBot Information:

https://www.storeitcold.com/