Research Highlights

Merging Cover Crop Use with Continuous Soybeans

By Barb Baylor Anderson

There are two increasing trends in Ohio: use of cover crops to enhance soil health and plant performance in crop rotations and the number of acres being planted to soybeans continuously. The question is how to merge the two so farmers maintain a successful, profitable strategy.

“The effects of cover crop planting date and termination date have not been studied on a whole systems approach, including the effect on diseases and pathogens, insects and yield,” says Laura Lindsey, associate professor in soybean and small grain production at Ohio State University and principle investigator of the Ohio Soybean Council checkoff-funded project. “While continuous soybean production is not advised, current economics favor it in many areas.” 

As such, the Ohio Soybean Council sees merit in the work. “Checkoff dollars we invest in plant research help equip farmers with the practices, tools and technologies to defend against yield robbers, while improving the yield potential and quality of our soybeans,” says Todd Hesterman, Ohio Soybean Council Research Committee chair and Henry County soybean farmer.

The objective of Lindsey’s cover crop research was to evaluate the effect of four cover crop planting dates and two cover crop termination dates on disease and insect pressure and yield in a continuous soybean system. The study was conducted in 2018 and 2019 at two research stations using a split-plot randomized complete block design with four replications. The main plot factor was cover crop planting dates from September to October. The sub-plot factor was cover crop early and late termination dates in the spring. 

Measurements included soybean stand counts, slug pressure, leaf area affected by foliar disease and insect defoliation, soybean cyst nematode (SCN) population, insect identification, insect pod damage, seedling disease-causing pathogen collection and isolation and yield data. 

Lindsey says in general, cover crops work well after soybeans since the grain is usually harvested in mid to late September, leaving up to two months of growing potential for a cover crop planted after harvest. However, because maximizing the cover crop’s growing time is so important, it may be necessary to consider specific soybean varieties.

“The biggest takeaway is that cover crop results will vary with spring weather,” she says. “A rye–oat cover crop mix may provide some rotational benefit, and in continuous soybeans, we are mostly interested in a non-legume cover crop like rye or oats. Leguminous cover crops, such as clover, can be alternative hosts for SCN, which is not good in continuous soybeans.”

Lindsey notes the research found the impact of cover crops on insect and disease pressure was mostly non-significant, but soybean stand and yield were significantly impacted by cover crop termination date. And although results varied greatly based on weather, she says farmers should focus on planting cover crops early in the fall to maximize cover crop biomass. 

“Farmers should also use water-holding capacity history of the field to determine the optimal termination timing,” she says. “If a field generally lays wet, a farmer should terminate late. If a field is well-drained, then a farmer should terminate early to conserve soil moisture. Farmers may want to plant earlier relative maturity soybeans, too, to allow for enough time to plant the cover crop since spring termination of the cover crop on time, again, is a critical factor.”

Published: Jan 25, 2021