If you were one of the many Iowa farmers who were hit with Sudden Death Syndrome (SDS) disease in your soybean fields this year, doing tillage on that soil and trying to bury the crop residue is not a good long-term solution. In fact, tillage can actually lead to poor soil drainage and cause soil compaction -- two conditions that promote the occurrence of SDS.
SDS is caused by a fungus present in many Iowa soils that infects soybean roots and produces a toxin that moves up the plant and kills the leaves. The weather in 2010 was ideal for the development of the SDS disease – temperatures below 60°F at planting, followed by moderate temperatures during the growing season, and constant wet conditions.
According to Iowa State University plant pathologists, there are a number of things farmers can do to prevent SDS from occurring.
- Plant resistant soybean varieties. Consult with seed companies and agronomists for information about varieties that are resistant to SDS.
- Grow SDS resistant soybeans in fields that have the greatest history of SDS problems.
- Take measures to avoid soil compaction or to reduce soil compaction.
- Plant later in the spring in those fields that have a history of SDS. You don't want to be planting beans in late May or early June—that will definitely lower your yield potential. But in fields where SDS has been a problem in years past, you may want to plant those fields last. In other words, try to get those fields planted in early May or by May 10 or so—as opposed to planting such fields in mid-to-late April.
- Consider improving soil drainage, if possible, in fields that have recurring problems with SDS.
Tillage can make drainage and soil compaction problems worse
Barb Stewart, state agronomist with the USDA-Natural Resources Conservation Service (NRCS) office in Des Moines, says conventional tillage will make drainage and soil compaction problems worse over time. In fact, Stewart says tillage reduces soil quality. "Tillage damages soil structure, reduces organic matter in the soil, and increases the risk of erosion," she points out.
Stewart says soil quality is directly related to soil performance. "Healthy, quality soil will do a better job of resisting erosion, cycling crop nutrients, supporting root growth, infiltrating water and sequestering carbon," she adds.
Reducing tillage also saves you money. "It means fewer trips across the field and less wear and tear on equipment," says Stewart. "Unless you just like wasting fuel, I ask that you do something else this fall and leave that crop residue alone which will protect the soil quality characteristics you've built over the last year."
For more information about Soybean SDS and how to manage this disease, call the Iowa State University department of plant pathology at 515-294-1741. Also, NRCS agronomic information is available at www.ia.nrcs.usda.gov/technical/.