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Alfalfa, pastures suffer from heavy rainfall, saturated soils

Purdue University News Service Published on 09 June 2011

Consistently saturated soils from heavy spring rainfall have taken their toll on some of Indiana's forage crops – especially alfalfa grown on soils that are less than moderately well drained.

Alfalfa samples that Purdue Extension forage specialist Keith Johnson has seen have suffered from too much moisture. "Alfalfa is the most prone to problems," Johnson said. "The plants are yellowing or showing a pea green color, which means soils have been too water-saturated for nitrogen fixation to occur."

The stress and moisture also can make alfalfa plants more prone to common diseases, such as spring black stem, rhizoctonia or phytopthora. While samples containing these diseases have not yet made their way to Purdue's Plant and Pest Diagnostic Laboratory, they have been common alfalfa diseases in past years.

As weather improves, Johnson urged producers to harvest their alfalfa crop when the crop is in late bud to very early flower.

"The best alfalfa growers can do at this point is hope for drier days and get out there and harvest the first cutting," he said. "They should evaluate which fields can be driven upon without damage to cut legume crowns or grass stem bases."

But even if producers are able to harvest the crop soon, the first cutting may not be a "grade A" feed crop, Johnson said.

"The stress means the protein content is down and that the energy content could be in question," he said. "As livestock producers balance livestock rations they should certainly analyze stressed crops before feeding them to their animals."

Livestock producers also may notice problems with damaged pastures, depending on soil types and the types of grasses present. Luckily, however, because temperatures have been cool during the recent floods and heavy rains, with the exception of a couple of days, stand loss shouldn't be as much of an issue as it would be in mid-summer.

"Heat during floods is much worse for pastures than the recent cool temperatures," Johnson said. "We have pretty resilient pastures, especially in southern Indiana where tall fescue is dominant, so livestock producers just need to think about soil types and let animals graze in areas less prone to damage."

If pastures show signs of damage caused by hoof action or water saturated soil, Johnson urges producers to continue to scout damaged areas and determine if reseeding is necessary, he said.

For cool-season grasses and legumes, like those common in Indiana pastures, the next ideal seeding time is August and very early September. Livestock producers also can wait to overseed in late winter months.

"Farmers can work now to get pasture fertility in line, control broadleaf weeds and then overseed in late winter," Johnson said.  FG

—Excerpts from Purdue University News Service