Cover crops are an important part of how Nick Wenning and his father, Roger, build up soil health and boost yields on their rolling, tight soils near Greensburg in southeast Indiana. Clover is one of Nick’s favorite choices to grow nitrogen and increase earthworm and microbe activity.

Sometimes they grow clover after wheat and then plant into it the next spring, Nick notes. His choice is to let the clover grow until planting, and then no-till directly into it before terminating it. Letting clover grow longer in the spring means more nitrogen is produced, which can be used by corn.

“We also sometimes include clovers in fall cover crop mixes after soybeans,” he says. “As long as they germinate and get up a bit before a freeze, they typically do well in the spring.”

While this timing is not as effective as establishing a clover crop earlier, like after wheat, it still provides diversity in the mix and brings along some benefits, he says. His father has experimented with all types of cover crops over the years, including brassicas, annual ryegrass, cereal rye, pearl millet and many more. One key is knowing what seeding dates and rates are optimum for various cover crop species.

Seeding date, species matter

In neighboring Illinois, Nathan Johanning, Talon Becker and Dennis Bowman, all with the University of Illinois Extension, set up trials comparing planting dates for two clover varieties commonly used in cover crop situations. Their results indicate that if you are after maximum benefit, sometimes measured in terms of biomass produced in the spring, it pays to know how various clover species respond to different relative planting dates.

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The Illinois researchers have looked at balansa and crimson clovers specifically. Their data at various sites in Illinois indicates a clear advantage for seeding clover in October vs. November. In fact, crimson clover seeded Nov. 22 at the Belleville location didn’t survive, yielding zero dry matter. Balansa clover survived, but biomass was greatly reduced versus earlier planting.

At Belleville in 2024, balansa clover seeded Oct. 19 yielded 4,281 pounds of dry biomass per acre, compared to 3,596 pounds when seeded Nov. 6. Waiting two more weeks affected stand, and biomass production dropped to 801 pounds per acre. For crimson clover, yields were much less, with 527, 244 and zero pounds per acre of dry biomass harvested from the three planting dates, respectively.

“Effect of planting date on survival and biomass production is definitely more pronounced in clovers than in commonly used grass cover crops,” Becker says. “There also appears to be a difference related to clover species.

“We saw an interaction with growing conditions at a given location, with balansa clover generally outperforming crimson clover at Belleville, but not necessarily at U of I’s Orr Research Center at Perry.”