WASECA, Minn. – The benefits of cover crops, preventing soil and nutrient retention are already known. Now the University of Minnesota is testing ways to successfully integrate cover crops into a corn-soybean rotation. There is no value in a cover crop if it cannot germinate and grow, there is also no value if that crop takes away yield from a cash crop.
At the University of Minnesota Winter Crop Days, the afternoon was devoted to cover crops. Extension agronomist, Scotty Wells, discussed research being done, inter-seeding cover crops at different growth stages of a standing cash crop and using different planting methods.
The different planting methods for the cover crop tested were a high clearance drill, broadcast with incorporation and direct broadcast.
“If the outcomes are similar to just directly broadcasting as the drill, then you probably do not need the drill and that was the way we set this study up,” said Wells. “We thought the drill would give us the best results, rather than just throwing some seed on the ground.”
The cover crop would need to establish sufficiently to survive the winter and come back the next spring for it to be successful. Different species of cover crop were tested.
“You don't have a huge set of plants to work with, cereal rye is the flagship, pennycress is pretty good too,” he said. “I would not want to stake my salary on red clover or hairy vetch to survive the winter.”
For this case, winter rye, hairy vetch, red clover and a fall mix were tested separately.
At V7, June-July, the cover crops were planted into standing corn using the three different planting methods. This was best management practice corn, Round-up Ready, kept weed free up to V7.
“Cover crops could be weeds, they use nutrients just like weed, the only reason they are not a weed is I put them there,” he said. “We asked the question, did we lose any yield, corn, of those cover crops we planted in there and the answer is no.”
Across all the site locations, the different types of cover crops and planting methods, there was no significant difference in yield when compared to each other and the control with no cover crops.
“All the site years, we never saw a yield reduction in corn,” said Wells.
Weed control does play a factor in maintaining yield. These were not weedy fields that were tested.
The next question of the study is whether or not the cover crops survived the winter and came back in the spring. They measured the biomass of each crop and planting method in mid-May, prior to termination and no-till planting soybeans.
“The reason we are after biomass is twofold,” he said. “If you are feeding it out, that's important for forage quality and it does have value for those that have animals that can feed it to. That's one and two, we are interested in nitrogen accumulation and protecting soil surface.”
For cereal rye, it did not matter how it was planted. With the average biomass across the different site locations, there was not a significant difference in spring growth when the rye was broadcast, broadcast and incorporated or planted with the high clearance drill.
“We did see, as you get in some of the smaller seed crops like hairy vetch and red clover, we did see an impact of incorporation, seed to soil contact,” he said. “They tended to do a bit better in that environment.”
Cereal rye also had the most biomass in the spring of all the cover crops tested. It averaged, across the planting methods, about 900 to 1,000 pounds of dry matter per acre.
Soil tests were taken in the spring at one-meter depth. The fields with the cereal rye cover crop showed a 50 percent reduction in available nitrate levels when compared to the control, best management practices and no cover crop.
“That is half that would be susceptible to loss or leeching,” said Wells. “That is soil that we would have stabilized as well.”
The soybeans that were no-till planted into those cover crops after they were burned down showed no significant difference in yield from the control, except for a slight yield loss where hairy vetch was planted. In the other cover crops, there was no yield gain or loss.