Nov 14, 2008
UK Asparagus Grower Extends His Season

Extending the season for fresh asparagus production in the United States would be of great benefit to the industry, from efficiencies of scale all the way to marketing. A United Kingdom grower has been experimenting with some innovative growing techniques that would allow him to harvest asparagus 37 weeks a year.

Cobrey Farms in Herefordshire, England, west of London, started planting asparagus in 2003, with a goal of having 1,000 acres by 2010 – with 600 of the acres under low tunnels, according to owner John Chinn. The farm currently has 734 acres in the ground, with 35 acres grown organically. Cobrey Farms also has small plantings of white and purple asparagus.

They quickly extended the harvest season to 17 weeks after the initial planting. They have steadily brought in new ways of extending the season and currently harvest the crop for the fresh market from late March to October.

The farm’s location in the Wye Valley, with its light, sandy soil, is perfect for asparagus production, with the south-facing slopes producing very early asparagus from late March and the north-facing slopes continuing harvest into July, Chinn said.

“Our goal is to be able to have supermarkets carry all-English asparagus from February until October,” he said.

To keep asparagus production going this long, Cobrey Farms starts by forcing the plants early with mini-tunnels over each row and a high tunnel with two layers of poly – what they call a “triple cover.”

After early production from the triple covers is finished, they move to fields with just the mini-tunnels and then to open-field production.

Cobrey Farms has tried many varieties, but has run up against winters that are too warm and wet for many of them. They tried Jersey Giant, but the plants never stopped growing in their climate. That variety will keep growing at 45˚ F and above. They have gone to mainly Dutch varieties because they don’t start growing until temperatures hit 50˚ F. One promising new cultivar from the United States is NJ 953, and Chinn said it looks like it might work.

Reverse season

For the summer and fall months, Cobrey Farms has developed a growing technique called “reverse season” that mimics Peru’s production season. They let the ferns grow up in the spring and early summer to help the root ball build up energy. They turn off the irrigation in early July, and by the third week of that month they can mow down the ferns and start harvesting a new crop of spears. Once production drops off with the cool, late-fall temperatures, the polythene covers are removed and all growth ceases for the winter. This late crop is harvested from July until the first weeks of October.

Yields vary greatly on the farm depending on the growing technique used. The open-field production yields 10,000 pounds per acre, the mini-tunnels 18,000 pounds per acre and the triple cover system 30,000 pounds per acre.

The asparagus is mostly grown in single rows 60 inches apart. Plant populations range from 10,000 plants per acre to 60,000 plants per acre according to variety and planned market. The new growing systems that Cobrey Farms has developed have resulted in higher plant populations than previously, with 13,500 plants per acre being the norm.

Packing line

To pack all of this asparagus, Cobrey Farms has invested in two optical sorting lines, like those used for apples, at $450,000 each.

The spears are brought from the field in the early morning and run through a washer and hydrocooler. The asparagus is then put on the beginning of the sorting line on a horizontal conveyor, with cups that hold one spear each. They go under the optical lens at a rate of 12 cups per second. The optical lens is hooked up to a computer that measures size, color, curvature and tightness of the head. The asparagus then goes down the line and the spears are dropped into vertical scoops. The computer decides which scoop to drop the spear into based on customer needs. When the scoop is filled, it opens up and a worker bundles the asparagus with an elastic band.

The system allows the perfect spear to be chosen to make the most optimal weight bundle. From the optical sorter, the bundles average 3 percent to 4 percent over weight, but the asparagus then passes down an average-weight packing line, which drops this give-away down to 0.3 percent over weight. This 3 percent savings has a big dollar impact when attached to the amount of asparagus that goes through Cobrey Farms. The operation has two of these lines, one with 50 chutes and the other with 80. It takes 600 workers in peak asparagus season to harvest and sort the crop.

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