FROM THE FARM REPORT: LESSONS FROM TWO YEARS OF DRONE COVER CROP SEEDING

Cover cropping is something we would like to do more of at Miner Institute. There are excellent incentive programs available for this practice, and the long-term benefits to yield, soil health, and edge of field losses have been well documented. The challenge is often just getting the seed out there at a time when bunks need to be covered, manure needs to be spread, and 5th cut is ready to come off. The low cover crop adoption rates should come as no surprise given that the optimal cover crop seeding window is also the optimal window for doing a whole host of other field work. In other words, the opportunity cost for the cover crop seeding window is too high.

It's also a time when field crews are desperately in need of a break. Custom applicators can be a valuable asset here… but they are also experiencing one of the most demanding times of year for their businesses.

When push comes to shove, and something doesn’t get done — the cover cropping takes the hit. But what if we could get the cover crop seed out before we started chopping corn? That’s the idea behind drone cover cropping. Broadcast the seed over the standing corn so that it can germinate whenever soil moisture allows and either grow underneath the corn or germinate soon after harvest.

Not only does this reduce traffic on the field, but the early timing allows for the use of some species that we normally wouldn’t be able to grow in a later planting situation. Furthermore, it moves the labor demand into a time when there is much less to do from a field crops perspective. Thus, the opportunity cost for cover cropping becomes much lower.

We have tried this method of cover crop establishment at Miner Institute for two consecutive years, with highly variable results. Last year, timely rains allowed the seed to germinate quickly after it was spread. This resulted in an excellent stand of annual ryegrass with similar fall growth to a single pass of annual ryegrass that was interseeded several months earlier as a check strip.

This year has been a different story. The anomalously dry soil conditions caused the seed to sit on the soil surface for weeks after it was applied. It was only after a few decent shots of rain and a broadcast manure application that the seed has finally sprouted. The improved seed-to-soil contact from drilling the cover crop would certainly have helped it emerge quicker, but I’m not necessarily sure that would have been a good thing. The young plants may have just sprouted and then withered due to the lack of moisture. All that being said, I’ve been quite impressed with the drone seeding results under the circumstances.

The DJI drones that were tested use a single broadcast spinner that covers a maximum broadcast width of 16-20 feet. We found that seed density makes a big difference in how well it spreads out, with denser seeds like winter rye spreading out wider than the lighter and smaller annual ryegrass seed. Even though it doesn’t broadcast quite as well, the small-seeded annual ryegrass at 25 lbs./acre took approximately half the time to apply as cereal rye at 100 lbs./acre.

While the jury is still out on the long-term utility of drones for cover cropping, the initial results suggest that drone cover cropping could soon be “taking off.”

— Allen Wilder

wilder@whminer.com