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2010-2011 Storage Carrot Trials

We used carrots as a model crop to study varieties, handling and storage options for long-term storage. Below are some findings from our study of six different varieties of storage carrots.

Methods

For the 2010-2011 season, we selected six storage carrot varieties (Bastia, Berlanda, Bolero, Canada, Carson, Sugarsnax) with varying maturity dates. Carrots (untreated, not pelleted) were seeded on June 28, using a Clean Seeder, in double rows 18 inches apart, hand weeded, and thinned to 1 inch on July 28 . Trickle irrigation was surface-applied along each row as needed.  We harvested carrots on four dates (September 29, October 12, October 27, November 10).  At harvest, carrots were sorted into marketable and unmarketable, based on the USDA United States Standards for Grades of Topped Carrots U.S. No.1 and U.S. No.2.  Unmarketable carrots included those that were too small, had insect damage, had splits or forking, were misshapen, or were hairy (excessive root growth).  We measured wholesale marketable weights, and counted marketable carrots and culls.  Standards for farmstands, farmers markets and CSA’s are more lenient including some forks, misshapen and smaller sizes and we also calculated direct market marketability. We evaluated flavor by measuring sugar content using the Brix test. 

All carrots were washed by hand in buckets and placed into storage at 32 degrees F and RH>95% in perforated plastic bags immediately after harvest. From December through March, we continued to sample Brix values and water loss of stored carrots.

Results

At Harvest (click to view image of graph)

Weight of marketable carrots appeared to increase across harvest dates for most varieties, indicating that carrots continued to grow late into the season without compromising quality from insects, disease, or other factors. Quality of Berlanda and Bastia, however, may have started to decline at the end of the harvest period. Brix score (sweetness) varied across harvest dates, and the date of highest sugar content varied with variety.  See the variety descriptions below for more information on marketable weights, culls, and reason for culling.

Storage (click to view image of graph)

Overall, Brix score (sweetness) appeared to increase during storage for the first several months and then decline rapidly. In our carrots, Brix score peaked at the beginning of February, after 3-4 months of storage. Water loss continued at low levels throughout the storage period, and averaged 5-11% between harvest and March 1.

Variety Trials

In 2010-11 trials, Bastia had the highest number of marketable carrots, followed by Bolero and Carson. Sugarsnax had the highest number of culls, particularly forked and misshapen carrots.  The following numbers are the average for all harvest dates. Marketable is for USDA wholesale standards.

BERLANDA (85 days) Dark orange, cylindrical, 9" Berlikum with good tops.  Source: Bejo.
Brix score: 7.27 Marketable weight: 50% Misshapen: 19%
Forked: 18% Insect damage: 8% Too small: 13%

BOLERO (75 days) Medium-long, 7-8" roots are uniform, thick, slightly tapered, and blunt, with a medium core and average internal color. This Nantes has good taste fresh, and after long-term storage. Resistant to Alternaria and Cercospora blight. Heavy, tall tops. Source:  Johnny’s.

Brix score: 7.89 Marketable weight: 42% Misshapen: 13%
Forked: 27% Insect damage: 8% Too small: 2010-4%, 2011-43%

CARSON (90 days) Early Chantenay, 7 1/2" deep orange, conical roots, with broad shoulder, blunt tip, and strong, tall tops. Source:  Bejo.
Brix score: 8.03 Marketable weight: 53%  Misshapen: 7%
Forked:  10% Insect damage:  13% Too small: 23%

BASTIA (85 days)  Smooth jumbo Flakee with deep orange color, 9" roots. Strong tops, stores well. Source: Bejo.
Brix score: 7.27 Marketable weight:  54% Misshapen: 13%
Forked: 18% Insect damage:  4% Too small: 8%

CANADA (95 days)  Dark orange, conical, 9" Chantenay with broad shoulder, strong tops, and long blunt tip. Source: Bejo.
Brix score: 7.62 Marketable weight: 53% Misshapen: 12%
Forked:  11% Insect damage: 6% Too small: 24%

SUGARSNAX (68 days) Smooth, deep orange Imperator has 9" tapered roots with strong, medium-tall tops resistant to Alternaria, Cercospora, and Pythium diseases. Tender and sweet. Source: Johnny’s.
Brix score: 7.65 Marketable weight: 28% Misshapen: 17%
Forked:  31% Insect damage:  16% Too small:  5%