The future of grazing research (2015)

Madeline Fisher With all the talk about maize, wheat, and rice production around the globe, it's easy to forget that the world's largest agricultural land use by far is grassland grazed by livestock. Grazinglands occupy some four billion hectares of the planet today, with 316 million hectares in the United States alone and another 200 million in Brazil—today's second-largest producer of beef behind the United States. Pasture-based dairying is also on the rise: New Zealand's dairy herd, for example, has doubled in the last two decades to 6.5 million animals, nearly all of which graze forage year-round. And the trend isn't likely to slow anytime soon, as consumption of meat and dairy products keeps climbing and consumers clamor for grass-fed beef. While the world's managed grasslands remain vast, however, the pool of scientists who study them is dwindling. In a 2009 paper that assessed the state of affairs in the southern United States, the authors reported a nearly 50% reduction in forage and animal scientists at land grant universities from 1984 to 2004, along with similar cuts to teaching and extension positions. And the situation hasn't gotten better since. “There are fewer numbers of grazing researchers now than anytime in last 50 years,” says ASA and CSSA member Twain Butler, a grazing systems scientist with The Samuel Roberts Noble Foundation in Oklahoma. One challenge is that forages are not considered a major commodity like corn or soybeans with “producer boards and check-off dollars to help fund needed research,” Butler says. Meanwhile, the funding sources that grassland researchers do rely on to answer producers’ questions have “dried up,” adds University of Florida professor and ASA and CSSA Fellow, Lynn Sollenberger. These realities explain both the attrition of grassland scientists and why those who are left must compete so hard for funds. But the community is hardly giving up. At the 2014 ASA, CSSA, and SSSA Annual Meeting in Long Beach, CA, Butler organized a symposium1 on the future of grazing research and its continued relevance as a science. That symposium has now become a special section of papers scheduled for the November–December 2015 issue of Crop Science, and alongside the obstacles are some definite opportunities. One of the biggest is grasslands’ unparalleled capacity among agroecosystems to provide ecosystem services. Beyond producing food, managed grazinglands can help improve water quality and soil health, promote biodiversity, increase wildlife habitat, mitigate greenhouse gas emissions…the list goes on and on. Twain Butler reviews tall fescue test plots. Photo courtesy of the Samuel Roberts Noble Foundation. Yet, we know relatively little about this potential today, Sollenberger says. “So, there's a need to broaden our traditional, production-oriented research themes and our research teams—which are heavy on forage agronomists and animal scientists—to address new categories of responses to grassland management practices.” He cautions, however, that while these areas do offer new avenues for research support, their investigation must be balanced with the continuing need of producers for applied information. And grazing research is full of other challenges, as well. Vast tracts of land and many years of data collection are required for experiments to achieve any semblance of the real world. Plus, research plots stocked with animals generally demand 24/7 attention. To those involved, though, the possible rewards are well worth the effort. “Just think how much more we could do for conservation if we could figure out a way for agricultural producers, the dominant landowners in North America, to do practices that would benefit conservation and not hurt production—or maybe even help production,” says Sam Fuhlendorf, a grasslands ecologist at Oklahoma State University. What follows are some examples of projects that are attempting to forge that future. USDA Photo by Lance Cheung. Tanner Ehmke Imagine bison roaming the Great Plains, grazing in dense herds and constantly on the move. Imitating that natural grazing pattern with modern livestock could make today's ranches more sustainable and productive. Mob grazing—also known as mob stocking—is under the microscope with researchers like ASA, CSSA, and SSSA member Ben Tracy, a grassland ecologist at Virginia Tech, comparing it to other forms of grazing like rotational and continuous grazing in a large-scale study on 150 acres in Virginia's humid grassland environment. After three years of conducting a study with funding from a USDA-NRCS Conservation Innovation Grant, Tracy and a team of researchers are analyzing the preliminary data for the potential benefits and drawbacks of mob grazing. The difference between mob grazing and other approaches to livestock and pasture management, he says, is livestock density and the amount of time grazing and resting the pasture. “Mob stocking is a form of extreme rotational grazing where you get a fairly high density of animals and you move them through paddocks much more rapidly than you normally would in a rotational grazing system,” Tracy explains. “The idea is that the animals will graze more evenly and maybe distribute manure and urine more evenly, but not graze everything to the ground.” The other key feature to very high stocking rates is allowing plenty of time for the land to recover. In a traditional rotational grazing program, a paddock might be grazed every three to four weeks. But in mob grazing, the pasture would be grazed once or twice a year. In continuous grazing, meanwhile, there is no rest period from grazing. Photo courtesy of Ben Tracy. Thanks in part of Allan Savory's TED talk on mob grazing, the practice has received a lot of attention in the popular press, Tracy says. Tracy hopes this study will help quantify the production and ecological benefits of mob stocking, including soil health, forage quality and species composition in Virginia. “We're trying to get some data to see whether mob stocking—at least here in our humid grasslands—is good, bad, or neither compared with other grazing systems.” While the data at this point is preliminary, Tracy points out that the observations gathered so far show that mob grazing does have ecological benefits. Higher soil organic matter is one benefit from mob grazing, Tracy notes. In the long run, improved soil health translates into a myriad of benefits like better water-holding capacity, climate resiliency, and overall productivity of the grassland. That's a significant benefit for grasslands facing drought conditions, he says. “In the fall, when we started to get some pretty good rainfall, we found that the grasses under mob stocking actually recovered faster,” Tracy says. “Once they got some rain, they recovered faster and actually had higher protein content compared with the other systems. So we think maybe that might be an indication of a more resilient system that can weather the drought a little better.” Tracy hypothesizes that the longer rest periods between grazing gives the grass a longer time to recover and perhaps put more energy into root growth, thereby increasing resiliency of the system. The higher amounts of residual grass trampled on the ground, he adds, may also help conserve water. The preliminary data also suggest that mob grazing also increases the amount of bioavailable or labile-type carbon in the soil, which Tracy says could be an indicator of carbon sequestration. With grazinglands covering about one-third of the earth's surface, there could be potential for reducing CO2 levels and having some effect on climate change. Mob grazing, however, has its challenges. Because of the high density stocking rates, Tracy figures about 30% of the forage is trampled to the ground and not consumed by the animals. ASA and CSSA member John Guretzky, a University of Nebraska–Lincoln grassland ecologist who is also working with a team studying mob grazing with funding from USDA-NRCS, agrees that the amount of forage consumption declines, which in turn, hurts average daily gains for the animals. “One of the challenges of mob grazing is when you're stocked at those higher densities, the animals are right next to each other and you can potentially limit their intake or their consumption of forage,” Guretzky explains. “If you're going to limit their intake, you're going to hurt animal performance and bring down animal gains and total production.” Tracy points out that with the frequent movement of animals from one paddock to the next, labor requirements are also significantly higher for the operator. Those drawbacks, though, may have a larger payoff. “It's important because grazinglands are such a huge part of the world,” Tracy notes. “So, how to manage them better is really something we need to know a little bit more about, but I think we still have room to learn.” John Morgan The idea is a wonderfully integrated one: To use fire to manage rangeland, improve forage quality, and enhance a host of ecosystem services. While the idea of using prescribed burning to benefit agriculture extends back thousands of years, however, a research-based approach to this type of land management is relatively new. Today, a main focus of this research is on “patch burning.” The practice entails conducting prescribed burns on sections of rangeland—patches—allowing livestock to graze these areas and then subsequently burning other patches to encourage livestock to shift their grazing pressure to new areas over time. This is then repeated continuously, creating a patchwork of rangeland habitat. This tool for managing grasslands helps rotate animals around grazinglands and provides them with better forage while also increasing vegetation diversity and improving wildlife habitat, among other ecosystem services. But the effects of patch burning on soil ecosystem services are not fully understood, and a recently published paper in the Journal of Environmental Quality1 explains the effects of this practice on water erosion and soil properties. “While patch burning may have beneficial effects on forage production and system spatial heterogeneity, it is also important to consider its implications on soil and the environment. The interactive effects of patch burning and grazing on soil properties have not been widely discussed,” say the paper's authors. The objective of their study was to examine the impacts of recently and older burned patches on water erosion, soil properties, and vegetation cover in eastern Nebraska. The study's lead author, ASA and SSSA member Humberto Blanco, associate professor at the University of Nebraska–Lincoln, explains that very little work has focused on the effects of fire on soil ecosystem services, so the team's study was an attempt to better understand those questions. What it demonstrated in the short term was an increase in erosion and runoff in burned areas. However, these areas recovered fairly quickly, with 60% of the ground having good cover after four months and returning to pre-burn conditions after 16 months. Photo by Brent Woods, USDA NRCS. “My overall impression—and the summary of this project—would be that the impacts on water erosion and other impacts are small compared with other management impacts we have seen in the past,” Blanco concludes. It is important to understand the implications for soil because the impacts on other ecosystem services and forage quality are notably beneficial. Indeed, John Guretzky, a grassland systems ecologist at University of Nebraska and co-author on the study, stresses that fire is an effective tool in rangelands for reducing invasive grasses and woody species while improving the quality of forage. “The big thing is heterogeneity. There is an increase in heterogeneity in vegetation structure with patch burning,” Guretzky points out. He explains that height and mass differences in vegetation are significant between areas that have been burned versus those that haven't and that grazing animals are in turn not only attracted to the shorter, new growth, but the quality of this forage is higher as well. Photo courtesy of Wikimedia Commons/Famartin What's more, grassland bird, invertebrate, and small mammal communities have been purported to benefit greatly from this heterogeneity, Guretzky adds. For their part, Blanco and his colleagues hope to study further the effects of burning in interaction with grazing both on topsoil and subsoil properties, particularly in the long term after multiple burning and grazing events. This is critical information to know, especially since what's happening above-ground with patch burning is not only encouraging, but also important for the bottom line. “In the southern Great Plains, you're out of business if you're in agriculture on rangelands and you don't have fire because of woody plant encroachment,” stresses Sam Fuhlendorf, a grassland ecologist and an expert in fire ecology at Oklahoma State University. But Fuhlendorf champions the use of fire for many other reasons, as well, including better forage, fewer insect pests like ticks on cattle, and enhanced ecosystem services like improved bird habitat, calling it all “a wonderfully interesting question of, how do you have all of those things?” Indeed, there is new energy with this integrated work to combine the needs and goals of agriculture with the stewardship principles and ideals of ecology. And these researchers agree that the field is welcoming this opportunity. “It's a really very exciting time when it comes to looking at these interactions among soils, grassland management, and livestock management,” Blanco says. Researchers are asking questions not only about how patch burning will affect livestock, but also soil ecosystem services including water erosion, water quality, wind erosion, soil structural quality, soil fertility, carbon sequestration, greenhouse gas emissions, water storage and conservation, and soil biodiversity. “So this is a fascinating opportunity to do interdisciplinary work,” Blanco says. “And this study is just on eexample.” Interested in this topic? Look for the Crop Science special collection on the Future of Grazing Research in the November–December issue. And check out the symposium from the 2014 Annual Meeting: https://dl.sciencesocieties.org/publications/meetings/2014am/13106.