What is in this article?:
- Including soybeans in crop rotation provides advantages
- Rotate crops and tillage
- Conditions that favor soybeans
In addition to increasing corn yields and cutting nitrogen expense, keeping soybeans in the rotation lowers next year’s corn rootworm management costs, says Ken Ostlie, University of Minnesota Extension entomologist. “Rotation resets the population of corn rootworms in a field, so you can get by with fewer rootworm inputs the next year. You can eliminate insecticide use, or plant all non-Bt corn that first year.”
Keith Schrader, farmer from Nerstrand, Minn., has learned he must rotate to soybeans for long-term rootworm control, since he’s had resistant rootworms on continuous-corn acres.
Rotate crops and tillage
Another advantage of keeping soybeans in the rotation is less need for tillage, Schrader says. On his erodible ground, he no-tills beans into standing cornstalks every third year. That’s followed by minimum tillage for first-year corn to incorporate nutrients. Even in the northern Corn Belt, Conley says, “no-till soybeans yield the same as tilled.” Likewise, there’s no yield benefit for tillage on first year corn after soybeans, adds Joe Lauer, University of Wisconsin corn agronomist.
To make the most of a corn-soybean rotation, though, “You need to treat soybeans as a first class citizen, rather than as a ‘rotation’ crop,” Conley says.
That can be a challenge for time-strapped farmers, Mueller points out. “Soybeans may get less attention because they respond less than corn to intensive management.” Still, Schreurs says: “Don’t treat soybeans as an off-year crop. Give it the same care you do your corn crop.” You should:
Select the best genetics. “Spend the time to select superior soybean genetics,” just as you do for corn, Conley says.
Plant narrow rows. Schreurs switched to 10-inch soybean rows for soybeans after University of Minnesota research showed a significant yield advantage. Research from around the country has affirmed that. For example, the multi-state, high-input USB-sponsored soybean trials, known as the “Kitchen Sink” study, found that narrow rows boosted yields by 3% to 5%, compared to 30-inch rows, Conley says.
Fertilize. Growers often neglect soybean fertility, Conley says, expecting soybeans “to scavenge whatever nutrients are left from the corn crop.” Schreurs does grid soil sampling yearly and applies phosphorus and potassium separately for both corn and soybeans. “Higher commodity prices allow us to run an additional pass with the fertilizer spreader.” What about foliar fertilizers? “You get more bang for your buck with soil-applied than foliar feeding phosphorus and potassium,” Conley says.
Apply preemergence herbicides. In the era of herbicide-resistant weeds, a total postemergence weed-control program is no longer prudent, Conley says. “There is a lot of data to show the economic value of preemergence herbicides” for soybeans, Conley says, “even if you don’t have resistant weeds.”
Invest in seed treatments. In Wisconsin trials from 2008 to 2011, seed treatments increased average yields from 0.6 - 2.3 bushels per acre. However, the probability of a profitable response depends on seed-treatment cost and crop value, Conley says. “Our experience has been that when spring conditions are cool and wet, and when planting date is in late April to early May, seed-treatment fungicides are an effective tool, especially given the current value of seed.”
Control volunteer corn early. Volunteer corn is very competitive with soybeans and also weakens the rotation’s value for managing corn rootworm, Ostlie says. These plants are “like a bridge from one corn crop to the next.”