Pasture renovation: refreshing a tired pasture
There are a variety of reasons to renovate a pasture. Long-term, continuous grazing encourages short growing forages like bluegrass and native white clovers that tolerate frequent defoliation to take over. If the turf is sparse, thistles may also flourish. Over-grazed pastures usually become little more than an exercise area after midsummer. Renovation may also fit into a crop rotation plan where a pasture is renovated, utilized for hay/silage for a time, and then returned to grazing. This article will address renovation for the purpose of improving the productivity of the long-term pastures.
Successful renovation will increase pasture production, as was shown in a three-year research project at the West Central Research and Outreach Center, Morris. The experiment was conducted on a pasture that had been grazed by beef cattle from May through September for at least 30 years. At the initiation of the experiment, the pasture consisted of primarily Kentucky bluegrass, smooth bromegrass, and quackgrass. 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.
Four forage species pastures were created:
- a pasture with no added seed
- a grazing alfalfa with low-set crowns to improve durability of the stand
- a mixture of red clover and birdsfoot trefoil, and
- 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, and rotationally grazed 5-7 times each of the next three years. Each rotation consisted of one day of grazing at 50 cows/acre followed by 20-35 days for regrowth, depending on growing conditions. Approximately 4" of residue remained after each grazing. Rainfall ranged from 12-16" during the grazing seasons of the study.
All renovated pastures out-yielded the unimproved pasture. Pastures renovated with alfalfa were 58-68% 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-$56/acre over 3 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.
The objective of another study was to identify forage species and nitrogen (N) fertilization combinations for pastures to feed grazing dairy cows. Forage species-fertilizer combinations were studied for three years. Combinations were Bromegrass with no N, Bromegrass with 50 lb/acre N in spring + 50 lb/acre N in summer, Bromegrass with 100 lb/acre N in spring, Bromegrass with 100 lb/acre N in summer and Bromegrass-Legume mixture but no nitrogen fertilization. Spring fertilization was before the first grazing of the year and summer fertilization was after the second grazing. Pastures were initially prepared by a glyphosate spray for weed control, fall moldboard plowing, spring disking and planting into a prepared seedbed. Pastures were grazed by lactating dairy cows 4-5 times per year for a 24-hr grazing period at a density of approximately 60 cows per acre. Intake was determined by difference of quantity of forage by clipping before and after grazing.
Forage species and fertilization effect on intake of grazing cows.
The impact of legume due to yield and nitrogen contribution on the intake by milking cows was impressive. No combination of N fertilization up to 100 lb/acre supported more than 40% as much forage intake as the bromegrass/legume combination pasture.
Presently alfalfa, orchardgrass and bromegrass mixtures consistently provide hardy productive pastures in western Minnesota. Local differences in soils and rainfall may favor a different set of species in other locations. Impressive stands of new varieties of fescue and ryegrass/white clover mixtures have been achieved on several farms, although long-term persistency is yet to be proven.
Data source: FINBIN
Published in Dairy Star April 8, 2006