Cover crop interseeding

By Clint Nester, Nester Ag, LLC

We have seen a recent uptick in interest for interseeding cover crops. In NW Ohio we typically struggle to diversify from cereal rye due to late corn and soybean harvest dates. Growers often tell us that airplane applications are too unpredictable and crops come off too late in the fall to utilize a drill. Interseeding  opens the door for earlier planting dates as well as additional cover crop species. However, there are multiple things to think about ahead of time before jumping in feet first.

Timing

Most of our growers that are interseeding into corn with a ground rig are seeding around the V5-V6 time frame in order to get the cover crop germinated prior to crop canopy. There are numerous companies now building interseeders: Fennig Equipment, Hiniker and Dawn Equipment have all developed variations of row unit type seeders. Additionally there are numerous broadcast options mounted on toolbars available. Loose soil following sidedress applications does seem to improve stand and help get the stand established. If a grower intends to broadcast into standing corn, adequate moisture and soil contact is critical.

For soybeans, we have not had many growers plant an early season cover crop. We have found the best timing to be when the bean leaves begin to turn yellow or just slightly before. Our takeaway from several years of observation is to go earlier rather than later. Take advantage of September fog days and heavy morning dews to help get the cover crop established. With either crop, seed to soil contact and moisture is key to a successful stand.

Species

Seeding into standing corn in June creates many possibilities of mixes that can be tailored to a growers individual goals. Growers have had good success with annual rye, crimson clover, hairy vetch, rape seed, buckwheat and cowpeas. In soybeans, a mix of cereal rye, barley and rape seed has performed well for several growers.  

Herbicides

Modifying a growers herbicide program is critical to successful interseeding. In many instances this seems to be the make or break item for interseeding. A program with no residual herbicide will provide the best option for cover crop success. Some growers have managed using an early pre with a post app of glyphosate or glufosinate prior to cover crop seeding. There is numerous university research on herbicide carryover and planting restrictions. Penn State has published an excellent resource on herbicide half life and gives some general cover crop recommendations: Common corn and soybean herbicides, estimated half-lives, cash crop restrictions and their potential to injure fall cover crops.

Rates

Seeding rates will need to be adjusted as seeding method is determined. Certainly, aerial applied covers need to be seeded at higher rates. However, some growers have found that more isn’t always better when looking at the final stand and managing cover crop growth. Growers may also need to adjust seeding rates based on cost, large seeded varieties seeded at high rates can add up in a hurry.

As with all things in agriculture, you need to have a plan. When deciding cover crop species and/or mixes, think through your ultimate goals for the cover crop. Are you trying to hold soil in place? Or maybe you want to use legumes to produce some nitrogen. The future crop rotation needs to be thought out in order to manage residue the following year. As mentioned before, your herbicide program needs to be well thought out ahead of time for your cover crop to have a fighting chance. Think through your seed purchasing and handling. We see many growers that decide to make last minute decisions on seed, and in todays world shortages and low availability are commonplace. Also think about how you plan to terminate your cover crop the following year. Will it be planted green or terminated before planting? Will you crimp it or use a chemical burndown? We have seen some great success stories with interseeded covers, just be sure you think ahead and plan for the unexpected.

Nester can be reached at clintnester@nesterag.com.