News : Advice for farmers who are facing flood-damaged crops

What was looking like a promising crop in 2010 has become a total loss for some farmers in eastern Iowa after the July deluge that resulted in record levels on the Wapsipinicon and Maquoketa Rivers, as well as other area rivers and streams. For corn and soybean fields that were totally submerged, it is doubtful that there will be much of a crop to harvest, so the focus should be on preparing for future year’s crops. Partially submerged crops may survive, but debris will need to be removed from the field to avoid damage to harvest equipment in the fall. Pastures that were submerged for a few days will likely survive, but mud and debris will need to be removed before the pastures can be utilized.

By the time corn and soybean fields dry out enough to walk in them it will be more apparent how much of the crop will survive. One of the first things that should be done is to check out the insurance options on the crop. Even if the crop is totally destroyed, there are things that should be done this summer and fall to restore the productivity of the soil. After removing debris, any sand and gravel deposits of more than 4” will need to be removed from the fields. Silt deposits can usually be worked in to the original topsoil. Since there is now new soil in the field, the soil fertility level has likely changed so the soil should be tested for fertility before planting the next crop.

To prevent soil compaction problems, avoid running trucks and heavy equipment over the wet soils. Most soils are not dry enough for traffic until the top 5-6 inches crumble, rather than slick over or pack. A cover crop such as oats or rye can help to keep weeds under control the rest of the season and can help to dry out waterlogged soils. New weeds may have been introduced to the field in the flood, so these will need to be managed in future years. There may also have been herbicides, such as atrazine, introduced with the soil. An oat cover crop this fall would also help to identify any potential future problems with herbicides in the introduced soil. The main concern with herbicide contamination would be for fields where a late summer seeding of forages will be attempted this August. Late summer forage seedings should be done by August 10-20. For more information on reseeding flood damaged forage crops in the late summer see Steve Barnhart’s article in the ISU Extension Integrated Crop Management News at http://www.extension.iastate.edu/CropNews/2008/0710barnharts2.htm.

Forage grasses and legumes can withstand a few days to a week underwater, but will not perform well if the soil remains saturated for several weeks after the water recedes. Any flood debris that will harm livestock or equipment should be removed as soon as possible. If flooded areas are recovering slowly and there are concerns about the viability of the stand, dig random plants in several areas and evaluate the condition of the root systems. Legume plants with a firm taproot, creamy white in color with no evidence of root rot, and that have green and visually healthy crowns and crown buds have the greatest likelihood for survival. These plants need a week or more of sunshine and drying soils. Legume or grass plants with watery, mushy, textured roots, yellowish or tannish in color, and those with no evidence of active crown buds will be the least likely to survive, even with good growing conditions during the next few weeks. For other information on dealing with the aftermath of the flood see ISU Extension’s Flood Cleanup website at http://www.extension.iastate.edu/disasterrecovery/flood.htm.