Grazing effects on soil water in Alberta foothills fescue grasslands
soil water content
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CitationNaeth, M. A., & Chanasyk, D. S. (1995). Grazing effects on soil water in Alberta foothills fescue grasslands. Journal of Range Management, 48(6), 528-534.
PublisherSociety for Range Management
JournalJournal of Range Management
AbstractGrazing can have a profound impact on soil water through its influence on infiltration via treading and on evapotranspiration through defoliation. Hydrologic changes in rangelands are most often associated with heavy grazing intensities although these changes do not increase linearly with grazing intensity. The objectives of this study were to quantify the impacts of grazing on the soil water regimes of sloped areas of the foothills fescue grasslands of Alberta. The study site was located at the Agriculture Canada Research Station at Stavely, Alberta. The effects of 2 grazing intensities (heavy = 2.4 AUM ha-1 and very heavy =4.8 AUM ha-1) for 2 grazing treatments (short duration = 1 week in mid-June and continuous grazing = May through October) were compared to an ungrazed control. The study was initiated in June 1988 and ended in April 1991. Surface soil water and soil water with depth were measured throughout each growing season using a neutron probe. Surface soil water (0 to 7.5 cm) across slope positions was lowest in the control and highest in the continuous very heavy treatments, but the trend in profile soil water (to 50 cm) was the opposite. Total profile soil water in the short duration very heavy treatment was greater than that in the continuous very heavy treatment, while soil water in the short duration heavy treatment was similar to that in the continuous heavy treatment. Vegetation at the study site was regularly water-stressed, as evidenced by soil water that was often below permanent wilting point, generally by mid-summer each year. Soil was near or below permanent wilting point in the autumn, regardless of its status throughout the growing season. Profile soil water was similar across treatments in autumn, indicating vegetation is using all available soil water. In contrast, soil water was generally near or above field capacity every spring, indicating the importance of snowmelt infiltration in these ecosystems. Only major (greater than 75 mm) summer rainstorms recharged soil water to field capacity. Thus it is concluded that maintenance of a vegetative cover that will trap snow for potential snowmelt infiltration is critical to soil water recharge of these ecosystems. Any grazing management regime that enhances litter accumulation and carryover should facilitate such snowmelt soil water recharge.
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Grazing systems, stocking rates, and cattle behavior in southeastern WyomingHepworth, K. W.; Test, P. S.; Hart, R. H.; Waggoner, J. W.; Smith, M. A. (Society for Range Management, 1991-05-01)Grazing systems and stocking rates are used to influence livestock grazing behavior with the intent of improving livestock and vegetation performance. In 1982, a study was initiated to determine effects of continuous, rotationally deferred, and short-duration rotation grazing and moderate and heavy stocking rates on steer gains, range vegetation, and distance traveled by and activity patterns of steers. Steers were observed from dawn to dark on 12 dates during 1983, 1984, and 1985, and activity recorded every 15 minutes. Eight steers per treatment (system X stocking rate combination) per date were observed in 1983 and 1984, and 10 per treatment in 1985. In 1984 and 1985, map locations of all steers were recorded at the same times as activity, and distance traveled summed from distances between successive map locations. In 1984, activity of 3 steers per treatment was electronically monitored during darkness. Steers grazed approximately 8.6 hr per day during daylight and 1.6 hr during darkness. Steers grazed an average of 8.9 hr/day during daylight under moderate vs 8.1 hr under heavy stocking, but stocking rate interacted with date in 1984 and grazing system in 1985. Steers traveled farther under continuous than under short-duration rotation grazing at both stocking rates in 1984, but only at the high stocking rate in 1985. Steers had to travel farther to water in the continuous pastures, and may have had to cover a greater area in an effort to select a more desirable diet, particularly under heavy stocking. These differences were not reflected in differences in gain among stocking rates or grazing systems.
Grazing systems, pasture size, and cattle grazing behavior, distribution and gainsHart, R. H.; Bissio, J.; Samuel, M. J.; Waggoner, J. W. (Society for Range Management, 1993-01-01)Reduced pasture size and distance to water may be responsible for the alleged benefits of intensive time-controlled rotation grazing systems. We compared cattle gains, activity, distance traveled, and forage utilization on a time-controlled rotation system with eight 24-ha pastures, on two 24-ha pastures grazed continuously (season-long), and on a 207-ha pasture grazed continuously, all stocked at the same rate. Utilization on the 207-ha pasture, but not on the 24-ha pastures, declined with distance from water. At distances greater than 3 km from water in the 207-ha pasture, utilization was significantly less than on adjacent 24-ha pastures, at distances of 1.0 to 1.6 km from water. Cows on the 207-ha pasture travelled farther (6.1 km/day) than cows on the 24-ha rotation pastures (4.2 km/day), which traveled farther than cows on the 24-ha continuously grazed pastures (3.2 km/day). Grazing system, range site, slope, and weather had minimal effects on cow activity patterns. Gains of cows and calves were less on the 207-ha pasture (0.24 and 0.77 kg/day, respectively) than on the 24-ha rotation pastures or 24-ha continuously grazed pastures (0.42 and 0.89 kg/da, respectively), with no differences between the latter. Calculated "hoof action" on the rotation pastures was less than that demonstrated to increase seed burial and seedling emergence. Intensive rotation grazing systems are unlikely to benefit animal performance unless they reduce pasture size and distance to water below previous levels, decreasing travel distance and increasing uniformity of grazing.