NDSU Extension Service, Published April 30 2012
Flooding poses soil management problemsFARGO - Widespread flooding, which made the 2011 growing season challenging for many North Dakota producers, continues to pose problems this spring.
One issue is managing these flooded soils now that the water has receded. Soil compaction and nutrient management are two major concerns, according to Chris Augustin, area Extension soil health specialist at North Dakota State University's North Central Research Extension Center near Minot.
Wet soils are more prone to compaction. Compacted soils lack pore space and restrict root growth and air and water in the soil. Augustin recommends allowing the soil to dry before starting field work to prevent compaction.
As floodwaters recede, they can deposit sediment, which can affect soil nutrient levels. Soil testing after soils have dried will inform a producer of a field's nutrient status. However, many of these areas were flooded for more than a month or two. This causes a lack of oxygen and drowns plants and beneficial soil microbes.
Arbuscular mycorrhizae are fungi that attach to plant roots and help plants attain nutrients such as phosphorus from the soil. They require live plant roots to grow. Therefore, fields lacking growing plants tend to have low amounts of arbuscular mycorrhizae. Crops grown in these areas tend to have phosphorus deficiencies, even in areas where soil phosphorus tests are adequate.
Research indicates that banding 60 pounds of phosphorus oxide (P2O5) per acre can improve corn yields in flooded fields. Soybeans and sorghum are fairly tolerant to this as well.
Augustin also recommends planting mixtures of cover crops if producers need forage. The mixture of different plant roots can help colonize the soil with a variety of different microbes. Generally, the shorter and coarser the roots, the more dependent the plant is on mycorrhizae.
Applying manure or compost at agronomic rates also can help bring flooded soils back into productivity. Manure and compost have beneficial microbes, fertility and organic matter. Adding these can speed up the process of restoring the soil biology.
"The most important thing to do is get something growing," Augustin says. "It will prevent erosion and help bring the soil biology back into the soil."