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Radish cover crops control weeks in wild seed production

Wild grass and flower seed growers can better control weeds by planting radishes as a cover crop prior to seeding, results of a trial at the Aberdeen Plant Materials Center show.

By John O’Connell

Capital Press

Published on September 10, 2013 2:37PM

ABERDEEN, Idaho — A researcher with the Aberdeen Plant Materials Center believes commercial wild grass and flower seed producers can better control weeds by planting certain species as cover crops.

Cover crops are planted primarily to improve soil health. Loren St. John, the center’s manager, explained managing weeds is a major problem in the commercial conservation seed industry because herbicides used to control broadleaf invaders also kill most flowers and grasses.

St. John has found that planting radishes as a cover crop reduces soil compaction through the deep taproots. Furthermore, radishes give off a chemical that delays the growth of weeds, giving grasses and flowers an opportunity to take hold without competition. A field of Appar blue flax he planted this season has provided St. John the first glimpse of the benefits to wildflowers grown following radishes.

“It was a beautiful field. It was the best field I’ve seen here in 20 years,” St. John said. “That’s something (commercial seed growers) may want to consider down the road is using a cover crop before they establish a seed field.”

St. John said radishes used as a cover crop also take up excess soil nitrates and spare growers the expense of having to mechanically prepare seed beds through cultivation. He said mustard and turnips also seem to stymie weed growth. Though St. John used radishes alone in his trial, he advises planting a mixture of cover crop species to maximize the soil benefit.

Delbert Winterfield, who raises grass and flower seed on dry land in eastern Idaho’s Swan Valley, planted a small acreage of radishes this season for his own cover crop experiment.

“We still have got to find something to control weeds in those wildflowers. I don’t have anything I can control weeds with other than mechanical cultivation or the old hand hoe,” Winterfield said.

Winterfield believes radishes will also help control soil nematodes. Winterfield has enjoyed strong sales lately of cover crop seeds to commodity crop growers. If his area receives enough snowpack to provide ample soil moisture this winter, he intends to plant radishes, turnips and other cover crops in order to both harvest the seeds to sell to customers and reap his own soil benefits in a subsequent flower crop.


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