Oilseed radish cover crops in sugarbeet rotations improves nematode control

When used in a sugarbeet rotation, oilseed radish can reduce sugarbeet cyst nematode populations, improve soil structure and improve yields.

Oilseed radish acreage has steadily increased in the beet producing area because of its value as a sugarbeet nematode trap crop and its ability to deeply root in the soil, improving soil drainage and aeration (Photo 1). Established in late summer it can exceed four tons of biomass per acre. It is an excellent scavenger of nitrogen from deeper soil layers after harvest of a cash crop. Upon decomposition, the nitrogen becomes available to the next crop.

Use only the oil seed radish varieties Adagio and Colonel because they are bred specifically to be used as a sugarbeet nematode trap crop. Oilseed radish releases exudates from its roots that stimulate cyst eggs to hatch. Nematodes then attach to the radish root, but are unable to adequately feed, and because of poor nutrition, either die or do not reproduce. This effectively reduces nematode populations and improves sugarbeet yield.

It is recommended that oilseed radish be used in conjunction with a nematode resistant variety (B-18RR4N or B19RR1N) as they work synergistically to improve beet yields (See Chart 1). Oilseed radish without the use of a nematode resistant variety will not maximize yield. Using radish will lower the risk of nematodes becoming resistant to the nematode resistant varieties.

Oilseed radish is effective planted anytime in a sugarbeet producer’s three- or four- year rotation. Most commonly radish is planted late summer following wheat harvest or very early-harvested dry beans at a 10 to 20 pound seeding rate. The heavier rate is more effective for nematode suppression. Ideal planting times are the first two weeks in August. When following wheat, best success has occurred after wheat stubble has been tilled. No-tilling into standing wheat stubble has not been very successful because growth is greatly impeded due to nitrogen being tied up. When planting behind wheat, a minimum of 50 to 60 lbs. of nitrogen should be applied. Radish should be tilled into the soil no later than green pod stage to prevent seed development.

Oilseed radish used as a cover crop has many benefits including improved soil quality, organic matter, nitrogen recycling, erosion control, reduced nematode populations, and improved soil structure and drainage.

Photo 1.
Photo 1.

Chart 1.
Chart 1 - Sugarbeet Yield following Oilseed Radish.