Rotate Crops Properly to Reduce Root Diseases, Boost Grain Yields

Proper crop rotations can boost wheat yields in western ND by an average of 40% by controlling root diseases, according to research at the North Dakota State University Dickinson Research Extension Center.

Producers who grow wheat in continuous rotations of wheat, barley, and durum lose about 40% of their grain yield to root pathogens, according to Roger Ashley, NDSU extension agronomist at the Center. Quality (test weight and protein) can also decline.

Data collected during the past four growing seasons in western ND show root disease is often difficult to diagnose. “Most pest problems are visible because they attack plant foliage or strike suddenly in confined areas, but root pathogens begin nibbling away at the root system even before the plant emerges,” Ashley says. “Symptoms develop gradually so the field appears ‘normal.’ It’s only when unfavorable weather for crop growth occurs that the damage from these pathogens becomes readily apparent.”

Research on the number of infectious spores per unit of soil have indicated that as the amount of time increases between wheat crops, there are fewer fungal spores to infect the crop. Crop rotations where wheat, barley or durum is grown once every three or four years allows naturally occurring microbes to break down disease-causing fungal spores. Spring wheat, barley, and durum are all host to the same complex of root diseases.

Ashley says that seed treatments can provide limited fungal root disease protection, but an integrated approach that includes crop rotation and seed treatments is much better.

He said broadleaf crops that work well in rotations with spring wheat, durum, and barley are canola, sunflower, safflower, pea, lentil, garbanzo beans, flax, and alfalfa. Ashley advises, however, that these crops must be put together in the right sequence, if other disease and management problems are to be avoided.

Corn, oat, millet, or sorghum should be included to reduce the risk of broadleaf crop diseases and diseases which impact wheat, barley or durum, says Ashley. Results suggest wheat followed by corn and then a broadleaf crop before rotating back to wheat is a good combination. Long-term rotations can include alfalfa, but producers should eliminate grassy weeds to obtain the maximum benefit in the control of root pathogens, says Ashley, as some grassy weeds are hosts for the same pathogens that attack spring wheat, barley, and durum.