As the weather through most of April and May has continued to look more like March and some additional rains are in the forecast, some producers are contemplating switching to soybeans. Soybeans are planted on a greater proportion of the production acreage each year in Ohio – close to 4.5 million acres each season. This means that approximately 1/3 of the acres have had soybeans continuously, which presents some problems. Here are some additional factors to consider while trying to assess what to do next.
For fields that have been continuous corn – target these first!! The year of soybeans will be great to help give a break to those pathogens that are residue borne. It will give that corn residue a chance to break down before adding to it. This is especially important if there has been gray leaf spot, anthracnose or northern corn leaf spot in the field.
For fields that were in soybeans in 2009-2010: Continuous soybeans lead to a build-up of both soil-borne and residue-borne plant pathogens. The worst culprits are soybean cyst nematode (SCN) and frogeye leaf spot. In Ohio, both of these pathogens have contributed to significant yield losses when susceptible varieties were planted in the same field year after year. SCN is best managed with crop rotation – primarily a non-host crop such as wheat or corn. Frogeye leaf spot is managed with resistant varieties – and avoiding planting soybeans in fields that had frogeye the year before. For those fields where you had been planting soybeans and were switching to corn – avoid switching fields where SCN has reached high numbers. It is important to keep the rotation scheme in place.
Check the resistance of the variety. The primary concern here is for Phytophthora root and stem rot. Not all varieties sold have high levels of partial resistance (tolerance) and unfortunately, these wet saturated soil condition have the pathogen “primed” for when soybeans are in the ground. For Ohio, varieties with Rps1c, Rps1k, Rps3 or Rps6 PLUS high levels of partial resistance are required for optimum stand throughout the growing season.
Treat the seed. Soybeans planted into soils that have been saturated need a seed treatment. There are a plethora of seedling pathogens in Ohio’s poorly drained fields and they need a seed treatment. Target products that will manage both the true fungi and the water molds.
From a soil fertility standpoint, switching to soybeans does not represent much of a change in your fertility program. Anything you did last fall in preparation for this year’s corn will be to the benefit of your soybeans. If you are breaking a continuous corn system with soybeans (while this may seem a bit early), plan on taking a nitrogen (N) credit next year when you come back to corn. For those who did apply anhydrous ammonia earlier this spring, soybeans will be N scavengers in an N-rich environment, so those applications will not adversely impact your soybeans this summer.
This year is starting out to be just as challenging as last year and the seed treatments will make a difference on final stand counts and potentially yields.