Recent heavy rainfall in some parts of the U.S. may lead to special concerns for hay producers who have been dealing with standing or flowing water and waterlogged soils, says Steve Barnhart, Iowa State University agronomist. He says it's important to avoid moving in to the hay fields or pastures too soon. Wet soils are susceptible to wheel traffic and compaction damage that can limit future productivity.

Barnhart recommends delaying harvest for a week to 10 days to allow the plants to recover. In addition, he says it's important to schedule a five- to six-week fall rest period for these stands.

Alfalfa, clovers and most forage grasses cannot live for very long under water. Most can tolerate a few days up to one week of flowing water. Standing water that "heats" in the sun and "cooks" the submerged forage plants is more of a concern and can kill or severely damage most plants within hours, according to Barnhart.

After the water recedes, an extended period of saturated soils continues to be reason for concern. Most forage plants can live for a week or two in saturated soils, but the lack of oxygen in the root zone will adversely affect their growth. These plants do not take up soil nutrients normally. Consequently, the root system deteriorates and legumes stop fixing nitrogen. They appear stunted and yellowish-green in color. If the soils drain quickly, plants begin to recover.

Barnhart urges producers to dig random plants in several areas and evaluate the condition of the root systems. The chances of survival are best for legume plants with a firm, creamy white taproot with no evidence of root rot. Green, healthy-looking crowns and crown buds are also positive signs. These plants need a week or more of sunshine and drying soils. Legume or grass plants with watery, mushy roots that appear yellowish or tannish in color, and those with no evidence of active crown buds, will be the least likely to survive.

Flooded forage may be silt-covered, which will add to plant disease potential, detract from the palatability of the harvested hay, and possibly affect silage fermentation. Pasture plants are affected much the same as alfalfa when under standing or flowing water and growing in water-logged soils. Grasses, however, are slightly more tolerant of these conditions than are legumes.

Source: Iowa State University.