Flood Recovery for Pastures

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First Step in Recovering Flooded Pastures and Hay Ground

Flood waters are receding, but the challenges in recovery for farmers and livestock producers are just beginning. Beth Doran, Iowa State University Extension and Outreach beef specialist, recommends producers get out in their fields as soon as possible.

“Beef producers should assess the damage to pastures and hay ground, then check out possible disaster assistance,” she said.

Doran advised cattlemen to look for three things in their assessment – debris, silt on the forage, and thinned or dead forage plants.

Cornstalks in fence row“Debris includes wire, metal and trash that may be injurious to animal health and is usually found along fence lines and in the corners of fields,” Doran said.

According to Brian Lang, extension field agronomist, silt on forage is a big issue because it is unpalatable and could carry microbes affecting animal health.

“Ironically, we need rain to wash off the silt. This early in the season, it is likely more rain will come," he said. "Otherwise, if the forage was tall enough, chop silted forage back onto the field to encourage clean regrowth. By the time farmers are able to run equipment on a pasture or hay field, visual assessment of forage species survival can be conducted and should be rather obvious.”

Whether the forage plants survived depends on three factors – plant species, time under water and how much of the plant was submerged. Some species, such as Smooth bromegrass, orchardgrass, fescue and ryegrass, should grow through a moderate silt deposit (less than 2 inches) and can withstand several days of flooding without injury. Reed canarygrass can stand longer submersion than other perennial grasses; whereas, Meadow bromegrass cannot tolerate any flooding.

Time under water affects the amount of oxygen available to the plant and is related to temperature, Lang said. Fortunately, during spring flooding, cooler temperatures allow plants to survive longer under water. Flash flooding – as opposed to standing water – increases survivability because the plants experience less oxygen depletion in moving water than still water conditions. Also, plants with more leaves above water are more likely to survive.

The USDA Farm Service Agency administers the Emergency Conservation Program, which provides funding and technical assistance for farmers to rehabilitate farmland damaged by natural disasters. Pastureland and hay ground are considered eligible land under ECP. Eligible practices pertaining to pastures and hay fields include debris removal (cleanup of woody material, sand, rock and trash on pastureland and hay fields) and restoring fences (livestock cross fences, boundary fences, and livestock gates.)

Producers with pasture damage or hay field damage are encouraged to contact their local Farm Service Agency Office to report the damage and determine if they are eligible for assistance. If the requirements are met, a formal application will need to be completed.

Step Two in Flood Recovery of Pastures Is Renovation

As flood waters are receding the renovation of flooded pastures is just beginning. Beth Doran, beef specialist, and Joel DeJong, field agronomist, both with Iowa State University Extension and Outreach, recommend producers check pasture plants for survival. They remind producers that forage production is a function of the plant species, and their density and growth. DeJong suggests evaluating live plants (plant vigor), plant density, and desirable species versus weeds.

Mahdi Al-Kaisi, extension agronomist and professor in agronomy, said flooding can flush nutrients necessary for plant growth out of the soil. With Al-Kaisi’s comment in mind, DeJong makes the following recommendation.

“If there is an adequate percent ground cover of desirable species, I’d recommend boosting production with the application of 50 to 80 pounds of Nitrogen per acre,” DeJong said. “Grasses usually respond the most to nitrogen fertilization, but soil sampling will reveal if other nutrients were flushed from the soil andPasture silt layer need to be replaced.”

Daren Redfearn, extension forage specialist with the University of Nebraska Lincoln, said the major flooding impact on grass pastures may also be due to excessive sediment deposits. Most perennial forages can produce new shoots and tillers if sediment deposits are less than 2 inches. In this case, crusting may occur, and light tillage will level sediment and enhance recovery. With deeper sediment, plants can suffocate and result in substantial stand loss. In these areas, mechanical removal is preferred to reduce plant loss and reduce the need for reseeding.  

“With thinner stands, interseeding with a no-till drill may be the best approach,” said DeJong. “If the stand is too thin, then complete renovation or reseeding may be needed.”  

If interseeding, consider what kinds of improved species to include in the seed mixture. For example, those more tolerant of wetter or drier conditions, close grazing or in rotation, or more tolerant of summer slump might be appropriate choices.

ISU Extension and Outreach publication “Selecting Forage Species” (https://store.extension.iastate.edu/Product/5367) could help with this decision. Also, the publication "Steps to Establish and Maintain Legume-Grass Pastures" (https://store.extension.iastate.edu/product/4332) might be of interest to those considering establishing and maintaining legume-grass pastures. Both publications can be downloaded at no charge from the online store or made available by the ISU Extension and Outreach county office.

Brian Lang, ISU Extension and Outreach field agronomist, recommends that producers treat new pasture like a newly established hayfield.

“In my opinion, the best way to start a new pasture is to treat it like a hay stand in the establishment year, if the terrain allows for a hay harvest,” Lang said. “Two hay cuttings provide time to establish strong root systems, and then include the area into your normal grazing system.”

With rougher terrain, interseed improved species and occasionally use a mower or a light flash grazing to reduce competition from weeds and established forage plants. Do your best to give the new seedlings a chance to root-down before incorporating the pasture into your normal grazing system.

Weeds also can be a problem in flooded pastures. Broadleaf herbicides can be applied to grass pastures; however, some of these herbicides have restrictions regarding new seedlings. In those cases, periodic mowing may be the best weed control option in interseeded stands until the new seedlings are established.

Doran reminds producers that evidence suggests these considerations: use of a sacrifice pasture while new stands are being established, the use of summer annuals, and/or fall grazing of cover crops. Iowa State University Extension and Outreach beef specialists and field agronomists are ready to help with questions and concerns on renovating pastures and establishing grazing systems.


Beth Doran
Extension Beef specialist

Joel DeJong
Extension Field Agronomist

Brian Lang
Extension field agronomist


Date of Publication: 
May, 2019