By Walt Fick, extension rangeland management specialist
Excessive rainfall in much of Kansas in 2019 has caused flooding. Vegetation response to flooding depends primarily on duration and frequency. Flooding impacts the amount of oxygen, carbon dioxide, temperature, and light available for photosynthesis. Impeded gas exchange results in a depletion of carbohydrate reserves, reduced energy available to the plant, disrupts cells, and impairs nutrient uptake, resulting in plant death. Loss of vegetation is also temperature dependent. It takes fewer days of submergence to cause stand loss as soil temperatures increase.
Most annual crops such as wheat, rye, oats, and barley tolerate only brief flooding i.e. 3-6 days. Cool-season perennial grasses such as smooth brome (24-28 days) and tall fescue (24-35 days) tolerate longer periods. Bermudagrass is tolerant of very long periods of flooding (45-90 days). Legumes that might be mixed with cool-season grasses including annual lespedeza (5-8 days), red clover (7-15 days), alfalfa (9-12 days), and white clover (10-20 days) are less tolerant to flooding.
Considerable variation exists among native grasses in their tolerance to inundation. Little bluestem tolerates only brief periods of flooding (3-6 days). Big bluestem and Indiangrass will tolerate only 7-14 days of flooding, whereas switchgrass tolerates 15-30 days. Eastern gamagrass will tolerate 10-22 days. Although buffalograsss is shorter than most species it will tolerate 45-90 days of inundation. A lowland species that is known to tolerate greater than 49 days of flooding is reed canarygrass.
Some invasive species such as yellow bluestem (3-6 days) and sericea lespedeza (10 days) have limited flood tolerance.
Flooding may indeed kill or damage many species, but certain species may survive. Sand deposition and lack of vegetative cover may require reseeding of flood-damaged areas. Consider planting species that are more tolerant of flooding, especially frequently flooded sites.
Reference: National Range and Pasture Handbook. 2003. Published by USDA-NRCS.
Photos below from southeast Kansas, courtesy of Jaymelynn Farney, beef systems specialist, Parsons.