Do pastures under management-intensive rotational grazing (MIRG) differ from grasslands under other management in terms of forage quality and quantity, carbon sequestration and biological soil activity? Not everyone believes the answers are yes, so researchers at the University of Wisconsin-Madison decided to run some trials to find out, comparing management-intensive rotational grazing to continuous grazing, hay harvesting, and unmanaged grassland. Their results point to managed grazing as a tool for improving forage production and quality on pasture.
Setting Up the Experiment
Gary Oates and Randy Jackson from the UW-Madison Agronomy Department conducted this research project at the UW-owned Franbrook Farm near New Glarus during the 2006 and 2007 growing seasons. The grazing season started in May and continued through October, providing six 30-day grazing cycles. Kentucky bluegrass and orchardgrass were the predominant grasses in all of the pastures. White clover was the dominant legume in the grazed plots, while birdsfoot trefoil was the dominant legume in the non-grazed plots. The researchers applied granular ammonium phosphate (11-44-0) fertilizer at the UW Extension recommended rate (50 lbs. N/acre) in early June of 2005, 2006 and 2007 to all plots except those under no agronomic management.
In this treatment, 25 cow-calf pairs grazed 20 acres for 28 days of every 30-day cycle. For two days of each 30-day cycle, the cattle were shifted to the MIRG plots.
Management intensive rotational grazing (MIRG)
The 25 cow-calf pairs from the continuous grazing treatment grazed a 1.5-acre paddock for two days in the MIRG plots, followed by a 28-day rest period. Typically, a six-inch residual was left after grazing. Cattle were returned to the paddocks on a 28-day schedule, rather than according to forage height and maturity, in order to hold the stocking rate constant between the continuous and MIRG grazing treatments.
Each cow-calf pair constituted 1.3 animal units (AU, or unit of 1,000 pounds of weight); each acre of rotationally grazed pasture had a stocking rate of 43.7 AU per month and each acre of the continuously grazed pasture had a comparable stocking rate of 45.3 AU per month. Over the course of the growing season, but mainly during the forage slump of summer, the livestock received feed supplements equivalent to 2.7 lb. hay DM (dry matter)/AU/day and 1 lb. cracked corn/AU/day in 2006, and 4.4 lb. hay DM/AU/day and 1.7 lb. cracked corn/AU/day in 2007.
Harvested and unmanaged forage systems
The remaining two treatments were managed without any livestock to mimic pastures enrolled in the Conservation Reserve Program (CRP). One of these forage systems consisted of plots of 0.75 acres each in which the plants were mechanically harvested to a stubble height of 2.5 inches in May, and again when the plants were 12 to 14 inches high. Because of dry conditions in 2006 and 2007, researchers made only two cuttings of hay. Average annual precipitation in this location is 35 inches; in 2006 the annual precipitation was 27 inches, and in 2007 it was 23 inches. The final control treatment consisted of 0.75-acre plots with no agronomic management, similar to land in the Conservation Reserve Program (CRP).
Monthly measurements showed that the potential utilizable forage from the MIRG plots was significantly higher than the other treatments. The plots with no management (CRP-like) had the lowest forage availability in both years. Looking at season-by-season data, the MIRG plots had significantly higher forage availability than all other treatments in spring and summer of 2006, while in 2007 this occurred in spring and fall. There was only one significant change in the makeup of the plant communities in the plots, and that was an increase in cool season grass cover in the harvested treatment.
The Relative Forage Quality (RFQ) of all treatments in the spring and summer of 2006 was less than 137. This is medium quality, providing the necessary nutrition for growing cattle to gain 1.3 pounds per head per day and lactating cows to produce 22 pounds of milk per day. RFQ in MIRG plots was significantly higher than the other treatments in the fall of that year and in summer and fall of 2007. The plots with no management had the lowest forage quality in both years.
Researchers Oates and Jackson were also interested in whether grazing practices that improve pasture productivity forage quality may also increase storage of atmospheric carbon in the soil, also called carbon sequestration. Carbon that is sequestered offsets carbon that is released to the atmosphere through the burning of fossil fuels, agricultural practices such as tillage, and land clearing activities such as deforestation. These kinds of measurements are difficult to take, and to quantify. What they did learn is that the MIRG treatment lost significantly less carbon in 2006 as compared to all other treatments. None of the treatments sequestered carbon that year. In 2007, the MIRG treatment was the only one that sequestered carbon. Oates says, “Perennial pastures have the potential for sequestering carbon, but the import and export of all forms of carbon across the farm boundary need to be considered in order to truly understand the farm’s carbon balance.”
Oates and Jackson also wanted to see if the higher level of plant production in the MIRG treatment was due grazing impacts on plant developmental stage and plant community composition, or was due to an increase in nutrients available to plants because of manure, litter and microbial activity. After analyzing microbial populations in the top six inches of soil in the four treatments, the researchers found the different treatments had no effect on total microbial biomass.
They concluded that higher production levels in the MIRG treatment were not due to soil microbial activity. Instead, greater production was a result of grazing resetting plant development and maintaining a preferred plant community composition because livestock are grazing down all plants in a brief interval as compared to continuous grazing, when they selectively and repeatedly graze down preferred plants.
So What Does This Mean?
If you think you’re seeing more and better forage thanks to your Management-intensive grazing, you’re right! If you haven’t started management-intensive grazing, you might consider how doing so might change and improve your operation and increase profitability.
MIRG may improve plant species diversity and even soil carbon but grassland wildlife habitat is not much better then severe continuous grazing.
That’s not necessarily true, Steve. Troy Bishopp’s farm is just one of many examples I know of, where the grazier manages rotational grazing for the benefit of the wildlife on and around his/her operation.
I know and respect you, Kathy, and have really enjoyed you studies, article and presentations, so treasure the dialogue. MIRG probably has more value to wildlife in drier environments (below 25″ annual precip.) where stock density is not over 1 animal/ac. but in higher rainfall regimes, it doesn’t bode so well for nesting and brood cover. There may be some individuals who see more wildlife (I’m not talking deer and turkeys that can survive in shrubs around a mall parking lot) but studies I’ve read show bobwhite quail, prairie grouse, upland sandpipers, and waterfowl decline or abandon MIRG pastures compared to continuous, moderate rotation, deferred rotation, and patch-burn grazing.
Good information, Steve. I would love to read the studies you’ve found. I think better understanding might help folks think of ways to modify management to meet wildlife goals as well. Perhaps after reading I can think of ways to help. Thanks for the dialogue and info!
Steve and Kathy,
Thanks to both for this dialogue. I need to check on my cattle, so references later and a few thoughts, perhaps not well connected:
—We’ve had a State Biologist (bird habitat specialist) and foresters on my land recently, considering how to manage our S. Appalachian farm for certain birds. I’ve decided for most of my land, increasing quail and some other bird habitat would necessitate keeping portions of my land in a state of transition between forest and pasture. With 40 inches of rain per year, this is an open invitation of severe problems with multiflora rose, autumn olive, ailanthus, and other invasives taking over, reducing/eliminating productive grazing ground, and delaying/preventing natural forest regen with it’s own soft and hard mast for wildlife.
—MiG, with selected 1-2x/yr clipping & hand cutting of above invasives has improved the carrying capacity of my land, greatly reduced my hay bill and feeding aggravation in our winter ‘wonderland’ of snow-mud-ice-mud where our ground never freezes.
—Having a dense, multi-species sod that cattle can feed themselves from with minimal soil & nutrient loss all winter, this is very poor quail habitat, but in balance it seems for me the best stewardship of non-forested, sloping ground with substantial, hard rains occurring any month of the year. On flat ground or more gentle slopes where all can be driven to, bunchgrasses may be more easily established and maintained, and invasive seedlings on the bare ground in-between more easily controlled.
—Not to overdo this, but certain species of birds depend on transitional forest edges; something that soils of any depth in my area do not stay in long without a lot of management; for soils, climate and rainfall here favor fast forest regrowth. European colonist methods of land clearing and farming have vastly increased productive spaces for certain native birds, but I want to keep in mind that these were developed by clearing the native forest that our 25+ inches of rain allows. Continual grazing can delay this forest transition, if the cows are hungry enough we can force them to feed as goats. Or we can commit ourselves to spraying and/or clipping on a regular basis to control these woody plants. What was the density of quail and some other native birds, before Europeans cleared these Eastern forests? I am ignorant on this…help appreciated.
—UT-Knoxville has some good research on using Native Bunchgrasses, for both grazing and bird habitat. Will post some of these references here soon. We do limit MiG access to pastures when we know birds are nesting there; primarily wild turkeys.
—I do notice on some of my steeper land, native bunchgrasses are returning. MiG and feeding late-cut hay there is replacing and building minerals and organic matter. Depleted from years of grazing with a single water source and shaded areas far away. Smaller paddocks through internal fencing, more water sources and nuturing a limited # of shade trees, nutrients eaten on these pastures are staying there. Thanks to Kathy, Jim Gerrish and others for helping me understand what we should be doing and why.
—So Steve, seems on my land that bunchgrasses are returning in the marginal areas of my land (fenced areas including some spots of shallow and steeper soils with some exposed rock). These are less marginal now (more cattle days per year), at least in part because all manure and urine stays on these areas while grazing. As opposed to the way those areas had been grazed by previous owner. And perhaps for most of the last 200 yrs??? We heard quail on two of these slopes recently, first time in the 9 years we’ve been here. They’ve been documented on a nearby property.
—Heading out now to work in a half-acre area above a pond. Native grass seedbank revealing itself after invasive brush mentioned above was cleared with a bulldozer last summer. But the transition now is messy, am paying a group of three guys to help this summer to clear this and other areas to try to get ahead of invasive shrubs and thorns.
In summary, seems that practices more toward either forest canopy or dense-mutispecies sod (with some scattered natives trees & shrubs) are working best now for fewer inputs and labor. MiG has delivered the high-nutritive quality sod; all we feed year-round is forage and hay. Still trying to learn how to manage that forest edge with minimal inputs and labor. Goats help!!
Thanks so much for sharing all this. It’s great information. I would love to read and hear more and share things with readers about how they can adjust their management to better protect wildlife. Anything you have would be much appreciated!
Kathy and Steve,
Here are a couple of references on managing forages for both beef cattle and wildlife; they do not directly compare MiG vs. other grazing methods, but do note timing of haying or grazing, and also residual heights after these practices necessary to promote wildlife use. Note these are based at U-Tenn, and the focus is demonstrating the value of native grasses as a forage, and also noting the wildlife benefits. The species composition of the forages has a big effect on wildlife use, and on my farm MiG has significantly increased diversity of plants in our pastures. Note also the use of buffers, to create wildlife habitat. As Steve noted, WHICH wildlife species you are hoping to attract affects management strategies.
Wildlife Considerations When Haying or Grazing Native Warm-Season Grasses SP 731-H
This one is longer; see Chapter 2 titled ‘Using Native Warm Season Grasses to Enhance Wildlife Habitat’. Sections in that chapter include wildlife as a primary objective vs. wildlife as a secondary objective.
U. Tenn. is the current leader in NWSG research. I know Keyser and Harper well and have been an editor on some of their literature.
BWQ need some low woody cover, between 5 and 25%, preferably not over 12′ tall (taller is more a predator perch than quality hardcore cover). Nwsg, moderately grazed season long, moderate rotation, or, better, patch-burn grazed produces the best nesting/brood cover and helps control invasive species. I still have to constantly basal treat woody invasives and, of course, sericea lespedeza is a never ending battle. Pasturegard works best but need to spot treat to protect important forbs. Grazing ensures travel lanes where rainfall is above 25″. Native warm-season grasses often return with any rotation but better the longer the rest but a very light stocking a few to several weeks after stock removal helps restore or ensure brood travel avenues.
There is a great deal of research needed on grazing and wildlife but, alas, very little has ever been done especially east of the plains states where it is needed most.
Recent techniques have vastly improved analysis of soil microbial communities. Would be interesting to know of more recent research, or that coming out soon, asking if and how MiG alters soil microbial diversity and health. Bigger soil critters as well…
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