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Challenges of the 2012 growing season monitored in Extension Service alfalfa plots

Jan. 17, 2013 | 0 comments

The combination of a very early start to the growing season and some late rains led to some fairly good yields of alfalfa at the Extension Service plots during 2012, attendees learned at the annual Agronomy Update meeting here.

A presentation prepared by Forage Specialist Dan Undersander and delivered in his absence by Extension Service Weed Control Specialist Mark Renz indicated that the first cutting was taken at the Lancaster plot on April 29 and that a fifth cutting was taken for the first time ever there.

At Arlington, the first cutting was taken on May 1, setting up a regrowth and harvesting cycle that led to total dry matter yields for the year at close to two tons per acre above the long-term average at Lancaster and one ton more at Arlington. At Marshfield, where no fourth cutting was taken because of the lingering drought there, the year's yield was on par with the average.

As was evident in 2012, soil moisture is a crucial variable in alfalfa yields, the presentation noted. It indicated that rain is needed by two weeks after a cutting, that the ideal for water availability is .2- to .25-inch per day, that stress begins when the supply is below 50 percent of that amount, and that two to three inches of water is needed to produce every one ton of dry matter yield.


Undersander's presentation noted that, despite their deep roots, alfalfa plants will shut down during drought and the yield lost during that period will never be recovered.

Linked to a shortage of water will be a higher leaf to stem ratio and a reduction in the percentage of neutral detergent fiber (NDF) - though this percentage is raised by high temperatures, thereby cutting the digestibility of the forage, the presentation explained.

What's common is that the NDF digestibility, and the potential for milk production, is highest with the first cutting of alfalfa and lower for cuttings taken during the warmest parts of the growing season, Undersander's presentation noted.

With this effect from temperature, late-season fourth or fifth cuttings should then have more favorable NDFs, digestibility, and milk production.

Despite the good results on 2012's alfalfa yields, at least in the Extension Service plots, Undersander and other Extension Service agronomists and specialists are concerned about the combination of stresses to alfalfa from the drought and diseases.

This affects the winter survivality - a concern that was alleviated somewhat by the snow cover that persisted in much of the state nearly until mid-January.


The 2012 new seedings were particularly vulnerable to stress, Renz indicated in delivering Undersander's presentation. He said that the alfalfa which was planted very early in the 2012 growing season fared the best in establishing itself.

Based on data from the Arlington plots and plenty of evidence elsewhere, there are definitely long-term effects on alfalfa stands and yields from problems experienced in the establishment year, the report indicated.

At Arlington, for example, the yields were better in 2012 from the seedings made in 2009 (a good year for establishment) than from those in 2010 and 2011, the report stated.

Stresses occur from frequent cutting, diseases, insects, and inadequate soil fertility, Undersander's report observed. Because of how important it is to build up the starch reserves in the alfalfa plant roots and to encourage extra root growth, the Extension Service recommends waiting until the blooming stage to take one of the cuts during the season.

During periods of drought, Undersander suggests cutting once the plant height has reached 10 inches and not leaving any more stubble than normal. Unlike with grasses, that's because the alfalfa regrowth comes from the plant crown rather than the stems, he explains.

From his perspective, Renz noted that attempting to control weeds in new alfalfa seedings by frequent cutting would defeat part of the purpose by weakening the alfalfa stand. "Baby the new seedings" in order to obtain a good stand establishment, he advised.

Regarding the proper date for the year's last cutting of alfalfa, Undersander's report suggested getting rid of the traditional Sept. 1 deadline and replacing it with a new criterion.

It would be based on the likely amount of remaining growing degree days - over 500 would allow enough time for regrowth and replenishment of root reserves while less that 200 GDD would limit new growth so little reserve energy would be drawn from the roots heading into the winter.


When alfalfa breaks dormancy in about three months, be sure to check for the number of live plants and stems, the report stated. That number should still be close to the minimum standard of 20 plants and 55 stems per square foot for an adequate stand in the autumn.

The report stated that the Extension Service plots did not meet that requirement in the counts taken a couple of months ago.

For thin alfalfa stands in the spring of 2013, Undersander's list of remedies includes interseeding with red clover, tall fescue, or orchardgrass, replenishing with alfalfa because autoxicity should not yet be a concern on a new alfalfa seeding from 2012, or disking the remaining alfalfa stand and starting anew.

Renz noted that the options for weed control are wiped out if grasses are part of the forage stand mix.

Depending on what kind of forage they might need for their livestock, farmers who are in short supply by the start of the 2013 growing season should consider forage oats or ryegrass for a relatively early harvest, Undersander's report indicated.

Other options are Italian ryegrass (a one-year crop) or perennial ryegrass.


Extension Service agronomists are also concerned with the apparent lack of attention to soil fertility on the part of farmers who pasture livestock. Their surveys indicate that two-thirds of them are not obtaining a soil fertility analyses.

On the question of applying Headline fungicide to alfalfa at a cost of about $35 per acre to control diseases, the results from three Extension Service plots in Wisconsin and two in Minnesota are not conclusive.

Part of the reason for the tests is the indication of some benefits by applying the product to corn and other crops.

The results varied significantly according to site but the treated plots produced an average of about 400 pounds more dry matter per acre. But a mystery yet to be solved is why the relative feed quality was lower in the treated portion of the first cutting.

On the economics of hay value, a single fungicide treatment would be a breakeven on a per acre yield increase of about 350 pounds if the alfalfa hay is sold for about $200 per ton. Prices for dry alfalfa hay were running at an average of $235 per ton at mid-December in Wisconsin.

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