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Extension > Agriculture > Dairy Extension > Grazing systems > Drought, winter-kill, drought, heavy rains: What's next for your pastures?

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Drought, winter-kill, drought, heavy rains: What's next for your pastures?

Vince Crary

Published in Dairy Star September 8, 2007

The weather these past two years has created many challenges for the grazing dairy farmer. Looking back, there was a serious drought for much of the state that curtailed forage growth from July to September in 2006, rains that brought recovery in the fall, winter kill of legumes, and another midsummer drought this year. Now there has been relief in much of the state but a deluge in the southeast. What can we do in the way of fall and winter management to restore pastures to good pasture production next year?

First, we need to avoid over-grazing of the new growth of grasses that came out of dormancy when rains came. The spring-like flush will soon slow down with the cool temperatures and reduced hours of daylight as we enter autumn. The forages will need to develop root reserves to enter winter in good health. There is a temptation to open all the paddocks and let the herd pick up what it can. Resist that temptation and continue to provide long rest periods between grazing events.

Next, we need to begin to assess the damage to pastures from two years of drought and a hard winter. If bare spots have been created, we can count on weeds, especially thistle, to move in. There may be a need to spray thistles this fall in preparation for pasture renovation next spring. It is now approaching a month late for planting grasses that will emerge and develop an adequate root system, although some people have had reasonable success planting so late that the seeds don't germinate until spring. Late seeding is very much like frost seeding, it is risky because you don't know what weather is ahead.

Fertility can be improved by applications of manure or fertilizer. Some people use pasture that needs fertility for a wintering area. As feeding areas are moved around to control the manure deposition by wintering cattle, considerable fertility may be added. Judicious management of winter grazing or feeding can be a tool for improving pastures.

Recent research from Great Britain has shown benefits in developing very diverse pasture species mixes. A diverse stand with multiple species of grasses and legumes is a well-adapted stand with benefits for the plants and animals. Plan for renovation next spring if the pasture stand has deteriorated and/or lacks desirable species mixtures.

Research at the West Central Research and Outreach Center in Morris assessed the benefits of early spring renovation of older bluegrass pastures. To prepare for spring renovation, the pasture was grazed hard the previous autumn and allowed to grow to about 6" height in the spring. A half dose of glyphosate was applied to set back, but not kill, the existing grasses. Determining the exact dose for setback is challenging as the amount of die-back is influenced by weather conditions that aren't known when the herbicide is applied. A week after spraying, the pasture was seeded with a no-till drill. Hard grazing immediately before renovating is an alternative, but less reliable, method of setting back old grass so new seedlings can become established.

Four forage species pastures were created:

  1. a pasture with no added seed,
  2. a grazing alfalfa with low-set crowns to improve durability of the stand,
  3. a mixture of red clover and birdsfoot trefoil, and
  4. a "graziers mix" that included alfalfa, birdsfoot trefoil, red clover, smooth bromegrass, orchardgrass, timothy, alsike clover and ladino clover.

The new seedings were grazed lightly the first year, then rotationally grazed 5 to 7 times each of the next three years. Each rotation consisted of one day of grazing at 50 cows per acre followed by 20 to 35 days for regrowth, depending on growing conditions. Approximately 4" of residue remained after each grazing. Rainfall ranged from 12 to 16" during the grazing seasons of the study.

All renovated pastures out-yielded the unimproved pasture. Pastures renovated with alfalfa were 58 to 68% more productive than unimproved pastures over three years. Renovations with red clover/trefoil were also more productive each year, although less persistent species in the mixes were declining by the third year. Over time, the pastures evolved so that alfalfa, orchardgrass and bromegrass were the most persistent species. Prorating the cost of renovation, $48 to $56 per acre over three years; the cost for each additional ton of forage produced was $8.07 for the alfalfa renovation treatment, $12.81 for the clover/trefoil treatment, and $9.95 for the graziers mix. The $8.07 per additional ton of forage cost associated with the alfalfa pasture renovation treatment is only about 10% of the cost of purchasing that extra forage as hay. Clearly renovation paid off handsomely.

Forage yield of three renovated pastures as a percent of the unrenovated control
Pasture renovation treatment 1 2 3
Control yield (tons/acre) 3.1 5.0 3.4
------ % of Control -------
Alfalfa 168 158 159
Red clover/trefoil 142 128 126
Grazier's mix 183 128 144

Finally, consider some of the new varieties that are coming available for pastures. A one-stop source of forage information is the University of Minnesota Forage web site.

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