Post-Harvest Handling Decision Tool > Crop Groups > Bulk Roots and Tubers

The removal of soil from bulk roots and tubers provides one of the primary means of quality differentiation for this group of crops. Crops are topped prior to storage, and washed using a combination of scrubbing action and pressurized water.

The cleaning methods used by Upper Midwest market farmers resemble those used on very large, commercial operations in their methods, if not their scale. Barrel washers and brush washers, similar to those used by market farmers, predominate on large operations.

On market farms that have not made the investment in mechanization, root washing takes place in a variety of innovative ways, either through pressurized water or agitation in a tank of water.

Manual Root Washing

At a very small scale, most market farmers choose to use a tray and a hose to wash roots. By attaching an inexpensive shut-off valve to the hose, a pressurized spray can be achieved by closing it part way, similar to putting one’s thumb over the end of the hose.

A logical next step might be to substitute an electric pressure washer for the hose and shutoff. Variable pressure is important to adjust for different roots; carrots and beets can withstand higher pressure for faster cleaning than can crops such as daikon radish. By shortening the wand, and twist-tying the trigger into the open position, the wand can be placed over the shoulder rather than supported in the style of a gun; this also increases the distance between the nozzle of the gun and the crop being washed. Using this technique, one hundred to three hundred pounds of roots may be washed per labor hour; beets and turnips wash up easily twice as fast as carrots and celeriac. Rock Spring Farm uses a 2000 PSI, 1.5 GPM model with adjustable pressure.

A less expensive, and less skill-dependent, method involves the use of a mesh bag to vigorously agitate roots in a 100-gallon Rubbermaid-style tub filled with water. Workers hold one top corner of the bag in each hand, submerge the produce, and shake and swish the bag in the water to scrub the vegetables against each other. The entire bag is then removed and dumped onto a sorting table or drying screen. Hog’s Back Farm reports rates of about 140 pounds per labor hour using this method.

Brush Washer

A brush washer makes a versatile addition to a packing operation for root crops, since it will gently wash beets, turnips, and winter radishes. Carrots and daikon radish tend to “skate” through without getting rolled around by the brushes; celeriac does not get adequate soaking and agitation to clean the convoluted roots.

Extra soiling on root crops, as compared to the tender fruit crops discussed previously, may make pre-soaking desirable in certain circumstances. Hosing down bins or totes of produce can improve the performance of the brush washer. In especially muddy conditions, an in-feed belt makes an additional rinsing step easier.

For root crops, a brush washer will clean about 300 pounds of roots per labor hour.

Barrel Washer

When it comes to washing roots, the barrel washer is the king of packing equipment. Made of wood or metal, a motor-driven barrel rotates to agitate roots in a bath or shower of water. Roots work their way through the barrel through the addition of dirty roots at one end, and a tendency of the roots to spread out in the barrel.

Two basic barrel designs are found on Upper Midwest market farms. In the one most common at the smaller end of the scale, a copper pipe with small holes in it runs lengthwise through a thirty-inch wide, eight-foot long wooden barrel. Water running through this pipe is pressurized through the holes, while the rotation of barrel causes up to 250 pounds of roots to slide up the walls of the barrel and back down again, creating a scrubbing action between individual roots. The barrel is supported by a frame with casters that support the hoops on the barrel; a small electric motor drives the rotation of the barrel by means of a sprocket and chain.

At a slightly larger scale, a second type of barrel seems to be more common. Rather than using pressurized water from a pipe, the barrel sits in a tank of water. Paddles running the length of the barrel lift the roots up and drop them back down into the water. While both types of barrel washer can bruise tender roots such as turnips and winter radishes, the paddle-style washer does much more damage.

Speed of operation is determined by the capacity of the washer. The smaller, smooth-walled barrel washer holds up to about 250 pound of roots, while the paddle-style barrels can hold much more. The rate at which roots go through, and how clean they get, is determined by how fast roots are added at the in-feed end. With both styles of washer, a gate on the out-feed end keeps a batch of roots tumbling in the washer until they are clean. At Rock Spring Farm, the author uses a smooth-walled barrel washer to clean five hundred pounds of roots per labor hour.

Some growers use an additional manually-controlled application of pressurized water at the out-feed to further polish the product.

With both a brush washer and a barrel washer, Linda Halley notes that in her previous experience, carrots, rutabagas, beets, and celeriac were handled with the barrel washer, while turnips and winter radishes were best handled with a brush washer.

This information is part of a Post-harvest Handling Decision Tool developed by Chris Blanchard of Rock Spring Farm in Decorah, Iowa. The tool is a project of the Fruit and Vegetable Working Group affiliated with the Value Chain Partnerships program. This project was funded by the Iowa State University Extension Value Added Agriculture program and the Leopold Center for Sustainable Agriculture. Blanchard conducted case studies of three vegetable operations to gather information for this decision tool. Products referred to in this tool are not an endorsement by Iowa State University.