Using spring seeded cover crops in sugar beets is a familiar practice for farmers, but many are asking about other ways to use cover crops in their system to accomplish different goals other than protecting sugar beet seedlings. Some are flying on a cover crop like cereal rye or barley prior to topping the beets, seeding smaller pre-harvest areas to help reduce erosion or seeding cereal rye post-harvest if time allows. There has been mixed success. A North Dakota State University Associate Professor, Amit Chatterjee, and his graduate student, Sailesh Sigdel, have been researching interseeding cover crops into sugar beets for the past three years. The Sugarbeet Research and Education Board of North Dakota and Minnesota has funded the research, and they're working with farmer-collaborator Glen Brandt.
First, they are working with various single species of cover crops in their replicated plots like mustard, flax, Austrian winter peas, winter camelina, cereal rye and winter wheat. They select species based on goals, for example, flax was used because the upright, stiff residue post-harvest may help with snow catch to recharge soil moisture. A legume (Austrian winter peas) was used to fix nitrogen during the growing season for the crop the following year. Overwintering species, like winter camelina, cereal rye and winter wheat, were selected to gain both benefits of water and erosion management in the growing season, post-harvest and the following spring. As we know, the first step to using cover crops in any scenario is to identify a goal.
Next, you may ask, why did they use single species instead of a mix? With research, it’s easier to evaluate each species individually than it is as a mix, especially when looking at a new practice. Using a single species may also be how a farmer approaches a new practice in their fields as well to keep it simple. In using this approach, they learned that cereal rye put on a lot of biomass and also took up variable levels of nitrogen – creating a tricky dynamic in this system with regards to root sugar yield and also harvest logistics. This would have been tough to learn if cereal rye was mixed with other species.
They also looked at timing of seeding. They seeded each species at two different dates, typically mid-July, and the dates are around 15-20 days apart. This was to find out if you can go in too early and compete with the sugar beets or too late where the canopy closure limits the cover crop growth. They found that biomass on the later cover crop seeding dates was limited and suggest going in at the earlier date and also using a more upright variety of sugar beets to maximize the system.
During this study, they have then been evaluating cover crop biomass, cover crop biomass nitrogen accumulation, yield and sugar content of the sugar beets. They are taking note on logistics of harvest and then also economic return. Overall, they are finding no impacts on sugar beet root yield, sugar content or economic return by interseeding cover crops while getting the added benefits of achieving specific goals like reducing erosion or managing nitrogen. They make the point that cover crops are not interfering with harvest logistics. Interseeding mustard or winter camelina at the later seeding dates had the greatest potential to increase economic return. These generalizations should be customized to meet goals of each individual farm.
The next step is going to be modifying equipment to seed the cover crops on a larger scale. But, as we all know, farmers are building and changing equipment all the time and they’ll find a way to make this practice work.