Looking to get more growth out of your cover crop? Try interseeding
One of the biggest hurdles when it comes to cover crops that we’ve found is finding the correct time to plant. There are a lot of factors that growers need to overcome for fall seeded covers to be successful. Late harvests, manpower, and weather among other things are very common factors that are out of our control that can impact cover crop success. One way to eliminate many of these issues is by interseeding.
Interseeding corn:
There are two time-frames for interseeding into corn; V4-V7 stages (before canopy) and at maturity.
Interseeding before canopy
Interseeding into corn between V4-V7 stages will give you the ability to establish a cover crop before canopy closure. This timing allows the cover crop to grow between rows of corn while the corn itself can mature enough that it can easily outcompete the young cover. This early establishment will promote increased nutrient retention, better erosion control, and weed suppression. It will also allow for an early start on biomass production for fall grazing.
Factors to consider:
- Equipment
Early interseeding has the most success when the cover crop is drilled. Companies such as Hiniker® produce interseeding toolbars that allow for twin cover crop rows in between 30" spaced corn. You might also consider Montag®'s 2208 bin system which allows you to apply fertilizer and cover crops at the same time.
Spreading is also possible but is much more dependent on surface moisture for germination. Modified high-clearance sprayers, such as a Hagie™, will allow you to drop cover crops directly between rows, eliminating pattern distortion from plant interference. Other high-clearance machines that are meant for spreading dry fertilizer can also be used but are limited by height.
- Cover crops
One of the best options for early interseeding into corn is broadleaf crops. Clovers and brassicas thrive with early establishment and can handle the decreased daylight as the corn canopies. Clovers especially are great for early establishment as they increase winter hardiness and spring growth while also increasing the amount of nitrogen you can credit. Annual ryegrass is another option especially if you are planting cover for fall grazing.
- Herbicide carryover
When early planting cover crops, note that corn pre-emerge herbicide carryover can be an issue with emergence. Most herbicide labels do not have specifications for cover crops to date, but much research is being done at the university level. Make sure to check your herbicide label for questions regarding control and planting restrictions. If you're intending to graze your cover, refer to the label for any grazing restrictions. For more information about herbicide considerations here is a great article from the University of Minnesota.
Interseeding at maturity
One option for early integration of more traditional winter cover crops includes interseeding around corn maturity. While this timeframe is limited to mostly broadcast application methods, it does give cover crops the chance to establish before harvest. It also allows the crop to have great seed-to-soil contact ahead of harvest residue. The ideal time for late interseeding is around the time when the black layer seals the kernel. This allows the cover crop seed to establish while in the cooler crop canopy. It can then take off more successfully as the corn matures and allows sunlight onto the soil surface. When it comes to this method, moisture is the key to success. Application may need to be timed around rainfall events to improve your chances of success.
Most growers that implement late interseeding use aerial methods or high-clearance sprayers to apply the seed. Numerous cover crop varieties can be implemented at maturity, but it is important to consider application rate, especially with aerial application. Cover crop species is another important consideration if using aerial application as smaller seeded cover crops typically do best with aerial application.
Note: more growers are experimenting with both airplanes and drones for aerial application with mixed success. Technology is advancing and we will continue to see improvements in this area.
Interseeding soybeans
When it comes to soybeans, timing for cover crop application around soybean senescence (beginning of soybean yellowing) tends to give the best results. This will allow your cover crop to establish without growing too tall and causing problems at harvest. Similar to interseeding in corn, most interseeded soybean cover crops are applied with aerial methods or with high-clearance sprayers adapted to apply seed. While research is currently underway around the ability to interseed early into soybeans, many risks play into this practice, especially when it comes to harvest. As this is a developing field, methods may easily adapt in coming years.
Other interseeding resources:
https://fwwa.org/2022/12/28/drones-cover-crops/https://efotg.sc.egov.usda.gov/references/public/IL/AgronomyTechNote21.pdf
https://agcrops.osu.edu/newsletter/corn-newsletter/2017-30/cover-crop-seeding-standing-soybeans
