Want to plant back to soybeans after the last soybean crop? Start with selecting the right variety.
With everyone looking for ways to trim costs going into 2016 there have been more questions about planting soybeans two years in a row. Economic studies show that even in times of low commodity prices yield is still the primary driver of profitability. Cutting costs at the expense of yield will not always improve profitability. That being said, input costs for soybeans are significantly less than for corn. Many producers in central Illinois will argue that corn is more profitable, but there is no denying a soybean crop requires a much smaller upfront investment.
In my career I have known a few producers who have planted soybeans after soybeans. Usually this has been to change a rotation or get a divided field put back together into one piece. Or maybe in a very wet spring when it gets too late to plant corn, some acres would switch to beans and end up being second-year soybeans. Generally speaking, these fields turned out just fine and growers were satisfied with the outcome. This does not mean they were their best beans or their most profitable acres, but a good crop was produced.
Soybeans are known to respond very well to longer rotations—meaning planting soybeans less frequently than every other year as you would in a standard 50/50 corn and soybean rotation. Fields that produce prize-winning soybean yields probably were planted to corn for 3 to 5 years or longer. With this trend it’s logical to assume that planting beans two years in a row would reduce soybean yields the second year. Without the right changes in management second-year soybeans probably yield less, but usually the yield loss is small enough it can be hard to prove.
If continuous soybeans do yield less it is most likely due to higher SCN and disease pressure. If you are considering some second-year soybeans next year careful variety selection and planning disease management practices help reduce the risk of incurring disappointing results.
Field selection also plays a major role. If you have fields that you know have a history of more soybean disease pressure or SCN problems you might be better off selecting different fields for your second-year soybean acres. Regardless of field history, select products that have strong resistance to SCN, SDS, BSR, white mold and Phytophthora. Any pathogen that overwinters in soil or residue is more likely to be a problem in second-year soybeans. When possible I would avoid planting the exact same cultivar two years in a row in the same field.
Are you using the right seed treatments to protect against seedling blight pathogens? If so, are you using ILeVO® to minimize the impact of SDS? And are you willing to treat with fungicide at R3 or even earlier if significant foliar disease pressure develops?
Personally, I don’t think second year or even longer continuous soybeans is something growers will make a habit of in Illinois … although it is already a common practice in some parts of the U.S. and in South America. But I do think it can be done successfully on a limited basis if you pay close attention to variety selection, field selection, right management practices and set realistic yield goals. Just remember that crop rotation is a good thing with proven benefits and with any crop moving away from rotation increases our production risk and requires a higher level of management to be successful.
Lance Tarochione is a technical agronomist with Asgrow/DEKALB in west central Illinois. His work has focused on crop production, research and product development, and through his role at Monsanto he currently supports the Asgrow and DEKALB brands in seven counties in western Illinois.