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October 21, 2004 Study Finds Grazing Affects Plants, Water Flow A North Dakota State University Soil Science Department professor’s recent study shows that grazing affects what happens below the ground’s surface. The study indicates rangeland that’s heavily grazed for an entire season or not grazed at all has few species of grasses and forbs growing on it, the plants’ roots don’t go very deep and rainfall or snowmelt runs off the land instead of soaking into the ground, said Jim Richardson, chair of the Soil Science Department. However, when cattle graze an area for just a few days at a time, the land has a mixture of grasses and several forbs, and the plants have deep, well-developed root systems. The soil also appears to be a darker, richer quality with numerous pores that can store water. The latter type of grazing is known as rotational or managed grazing. Ranchers divide their rangeland into a system of several pastures, a process called cross-fencing, and move their herd from one pasture to the next. Ranchers usually keep their cattle in one pasture no more than about three weeks. The length of time depends on the size of the herd and other factors, including rainfall and how well the grasses and forbs have recovered from the last round of grazing. The cattle generally graze in the same pasture only two times per season. Richardson says rotational grazing is closest to the way the buffalo lived, staying in an area until the grass was gone, then moving on. The study explains what people have observed for some time about the effect of rotational grazing on rangeland, said Paul Nyren, director of North Dakota State University’s Central Grasslands Research Extension Center near Streeter. “ ‘Where did the forage come from?’ was always the question,” he said. Short-term grazing helps plants grow because it releases carbohydrates stored in the roots, according to Richardson. The carbohydrates rise to the top of the plant to continue the photosynthesis process and quickly generate strong, new growth to replenish what the cattle eat. Nyren said the ability to capture moisture in the soil is vital, particularly in parts of the state that can’t get through a grazing season without running short of water. If rainfall or snowmelt can soak into the ground, it’s there for plants to use when they need it, and it’s not causing flash flooding or erosion problems, he said. Areas with rotational grazing also develop better habitat for ducks, grouse and other wildlife, Richardson said. “I’d never go back to season-long grazing,” said Gene Goven, a rancher and farmer near Turtle Lake who has been doing rotational grazing since the 1980s. He said he found that the prairie potholes on his land didn’t fill as fast after a rain, but the water was clearer and water levels remained more stable between rains. He said he also discovered he can raise more cattle and let them graze longer and the cattle gain more weight under rotational grazing. Richardon’s study is a follow-up to research he and others conducted on Goven’s land in central North Dakota in the early 1990s. In the latest study, Richardson, with help from Jay Volk, an NDSU graduate student working on his doctorate in animal and range sciences, and about a half-dozen students and technicians from the university’s Soil Science and Animal and Range Sciences departments, collected data in just 4 1/2 days during May on the Central Grasslands Research Extension Center. Natural Resources Conservation Service soil scientists helped by recording the field description of the sites where the team took samples. The research team did its testing in three areas. One site hadn’t been grazed, another was heavily grazed and the third was part of a rotational grazing system. The team used a backhoe to dig a trench 60 to 70 feet long and about 5 feet deep perpendicular to the slope at each site, then took samples at various depths. Richardson said the researchers collected all the samples at about the same time to make sure they didn’t run into any seasonal changes that might alter plant and soil conditions. “It took a huge crew of really hard workers,” he said. The researchers are analyzing the samples and, so far, they’re seeing about what they expected, Volk said. Their next step is preparing a paper on their findings and getting it published. Volk said he’s also scheduled three talks on the research. One is during the Central Grasslands Research Extension Center’s grass and beef day Jan. 19. He’ll give another talk at the Society of Range Management’s annual meeting in Fort Worth, Texas, in February. Richardson said the results are similar to what Extension range science researchers at Colorado State University have found. ### Source: Jim
Richardson, (701) 231-8903, jimmie.richardson@ndsu.nodak.edu
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