AUBURN UNIVERSITY, Ala.—North Alabama farmers are managing fields in different ways this spring. Excessive rainfall and subsequent floods are creating additional hurdles for spring field preparation and pasture quality.
Dr. Audrey Gamble, an Alabama Extension soil scientist, said erosion, sediment, deposition and crop residue accumulation can leave fields in need of significant physical repair after a flood.
“It is extremely important to let soils drain prior to working in fields, since operating equipment in saturated soils can cause severe soil compaction, which has a negative impact on soil water infiltration and crop growth,” Gamble said. “Large debris should also be removed from fields prior to reworking soil.”
Crop residues and sediment deposits can accumulate quickly. Different accumulation levels can be handled in a few different ways.
Accumulation less than four inches deep can be incorporated into the soil using conventional tillage methods. If sediments or residue accumulates four to eight inches, deep tillage to twice the accumulation depth with a moldboard or chisel plow may be necessary. Minor ditches and gullies as a result of erosion can also be corrected with tillage. Larger gullies and deep sediment may require extensive repair with earth-moving equipment.
Contact the local NRCS office to determine whether there are assistance programs to help restore damaged farmlands.
Allow soil to drain, then collect soil samples to determine fertilizer and lime requirements needed to restore crop productivity. Some soil microbial populations may be significantly reduced under flooding conditions, so it is important to inoculate legume crops, such as soybean, following a prolonged flood event. Cover crops can be used to prevent further erosion if cash crops are not going to be immediately planted.
Dr. Leanne Dillard, an Alabama Extension forage systems specialist, said pastures and hayfields should be surveyed for debris and large gullies.
“Light disking or dragging may be required to even soil surfaces, but conventional tillage is likely not necessary,” Dillard said. “Once the soil surface is smooth, cultipacking will firm the soil and allow for a better planting surface.”
Reseed fields using a grain drill, a no-till drill or broadcasting. Use a sprigging machine to sprig hybrid bermudagrass. Dillard said producers should take care to follow specific recommendations for each forage species on soil fertility, planting dates, seeding depth and seeding rates. Information and recommendations can be found online at www.aces.edu or by contacting the local Extension office.
Flooding Affects Plant-Available Nutrients
Flooding can result in loss of plant-available nutrients in several ways:
- Surface-soil erosion can result in loss of valuable plant-available nutrients and organic matter as runoff.
- Nutrients that are prone to leaching—like nitrate and potassium—can be lost to ground water.
- Gaseous losses of nitrogen can occur in water-saturated soils through denitrification.
Gamble said agronomic soil testing is recommended following flooding events to assess soil plant-available nutrient contents.
“After periods of prolonged flooding, phosphorous deficiencies can occur even if soil tests indicate an adequate plant-available phosphorous concentration, since flooding can reduce populations of soil microorganisms responsible for increasing the availability of phosphorus,” Gamble said.
Both public and commercial laboratories can test for plant-available nutrient content.
Contact the Auburn University Soil, Forage and Water Testing Laboratory for questions about sample collection.
Auburn University Soil, Forage and Water Testing Laboratory
961 S. Donahue Drive
Auburn University, AL 36849-5411
Phone: (334) 844-3958
Potential heavy metal contamination is dependent on proximity to polluted areas. Heavy metal contamination can be traced to industry wastes, mine tailings, wastewater treatment, pesticide applications, leaded paints and many other sources.
Gamble said Extension agents and county health departments can likely provide information on region-specific contaminants.
Soil samples for metal analysis can be collected and shipped in the same way as an agronomic soil test sample. Contact your preferred soil laboratory for specific instructions on sample collection and shipping.
Pesticide residue-contaminated soils is unlikely to pose a long-term threat in flooded fields, since most pesticides break down relatively quickly in soils. Gamble said there are cases where pesticide safety may be an issue, though.
If pesticide contamination is suspected, contact the state pesticide regulatory agency for further assistance.
For more flooding resources, visit www.aces.edu.