Make sure fields are ready after continuous corn

Farm Forum

INDIANAPOLIS — Thinking about putting soybeans back into your rotation next season? If you’ve been following a corn-on-corn cropping strategy in recent years, plan ahead to make sure your fields are ready for the switch to soybeans.

Andrew Ferrel, Mycogen Seeds agronomist, recommends four steps for successfully rotating to soybeans.

Start with a clean field. Corn crop residue can take a significant amount of time to break down, creating a barrier for young soybean seedlings, especially in reduced-till or no-till situations. These conditions tend to keep springtime soils cool and wet longer, creating a favorable environment for early season fungal pathogens.

“Soybean yields can be highly affected by poor emergence and early vigor,” Ferrel says. “It is important to get soybeans off to a good start with an even and well-established stand. In some cases, light tillage of heavy corn residue may be needed to create a clean seedbed for good seed-to-soil contact.”

Head off emergence issues. Many factors can compromise seedling emergence, including insect pressure and seedling diseases. Under these conditions, Ferrel recommends a seed treatment to help promote a strong stand, and thus, earlier canopy closure and improved yield potential.

There are several seed treatments in the marketplace, many containing fungicides and insecticides in one product, Ferrel notes. “The combination products are often worth the minimal added expense to provide extra protection for soybean seedlings, especially when planting in less-than-ideal conditions,” he says. Consult with your local agronomist or seed supplier for seed treatments appropriate for your area.

Consider soil inoculants. Years of corn-after-corn production can reduce populations of Bradyrhizobium japonicum, the soil bacteria that fix nitrogen (N) for soybeans. Fields that have been out of soybean rotation four or more years could benefit from an inoculant to ensure proper nodulation and prevent the need for supplemental N applications.

“Inoculants generally are very inexpensive relative to other crop inputs, and they are worth the investment in such cases,” Ferrel says.

Watch nutrient levels. Corn is responsible for significant removal of key soil nutrients, particularly N, phosphorus (P) and potassium (K). Corn’s high affinity for N means that growers must apply high rates of fertilizer each year to achieve desired yield. These N applications can result in rapid changes in soil pH. Before planting soybeans into these fields, take soil tests, paying special attention to P and K and soil pH levels, and adjust for soybean needs.

“As you plan for 2015, assess your fields and determine which are best-suited for soybean production,” Ferrel says. “Your trusted agronomic adviser can help you select varieties with the greatest yield potential after continuous corn. Additional agronomic resources are available on”