• Applicability of the Kostiakov equation to mixed prairie and fescue grasslands of Alberta

      Naeth, M. A.; Chanasyk, D. S.; Bailey, A. W. (Society for Range Management, 1991-01-01)
      The Kostiakov equation is of interest in rangeland hydrology because it is a simple 2 parameter equation with values of constants easy to determine from measured infiltration data, and because of its reasonable fit to infiltration data for many soils over short time periods. There is, however, some controversy in the literature regarding its applicability to rangelands. The Kostiakov infiltration equation was examined to determine its suitability to characterize infiltration on mixed prairie and fescue grassland ecosystems in Alberta, Canada. The infiltration data from double ring infiltrometers fit the Kostiakov equation very well. Of 26 regressions, 10 had an R2 over 0.95 while another 8 had an R2 over 0.90. The average R2 for all data at a site was 0.931 for mixed prairie, 0.857 for parkland fescue, and 0.938 for foothills fescue grassland. Changes in antecedent soil water and different grazing regimes altered the 2 equation parameters. Intercepts consistently declined with intensity and earliness in the growing season of grazing, although there were no consistent treatment trends with grazing. The Kostiakov equation is considered a good equation for infiltration in the 3 grassland ecosystems studied. Although parameter m had a narrow range of values for all 3 ecosystems and an average value from this study could be used, parameter a limits the equation and field testing is required for its determination.
    • Grass utilization and grazing distribution within intensively managed fields in central Alberta

      Irving, B. D.; Rutledge, P. L.; Bailey, A. W.; Naeth, M. A.; Chanasyk, D. S. (Society for Range Management, 1995-07-01)
      Grazing distribution and grass utilization was evaluated in intensively managed fields in the southern Aspen Parkland near Kirriemuir, Alberta. Three fields, 130 ha in size (with dimensions .4 X 3.2 km) were grazed by 1,000 cow/calf pairs for 5 days each. Stock water was accessible only from one end of each field. Grazing distribution was evaluated by monitoring grass utilization daily during grazing and after grazing at 0.1, 0.8, 1.6, 2.4, and 3.1 km from water. Final utilization did not differ within fields, except for a decline at the maximum distance from water (3.1 km). Temporal utilization patterns existed and could best be described as a wave, with defoliation beginning near the water source on day 1 of grazing and proceeding outward from water until the ends of the fields were grazed on day 5. Final utilization was uniform; selective grazing of areas close to water was not removed by intensive management, but was masked by a rapid rate of defoliation.
    • Grazing effects on soil water in Alberta foothills fescue grasslands

      Naeth, M. A.; Chanasyk, D. S. (Society for Range Management, 1995-11-01)
      Grazing 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.
    • Grazing impacts on litter and roots: Perennial versus annual grasses

      Mapfumo, E.; Naeth, M. A.; Baron, V. S.; Dick, A. C.; Chanasyk, D. S. (Society for Range Management, 2002-01-01)
      Soil carbon (C) and nitrogen (N) storage in grasslands is a function of litter and root mass production. Research on how annual grasses compare with perennials for above ground and below ground mass production, and contributions to the soil C pool under pasture management is scarce. The objective of this research was to evaluate grazing intensity effects on litter and root mass, C and N pools of perennial grasses, smooth bromegrass (Bromus inermis L.) and meadow bromegrass (Bromus riparius Rhem.), and the annual grass, winter triticale (X Triticosecale Wittmack). Litter mass and C pool for the perennial grasses were greater than those for triticale. Litter C and N pools generally decreased with increased grazing intensity. Root mass was greater for the perennial grasses than for triticale at all grazing intensities. Meadow bromegrass generally produced more root mass than smooth bromegrass. Root C and N pools for triticale were 31 and 27%, respectively, of that for the perennial grasses. Estimated total C contribution (roots and litter) to the resistant soil organic C pool was 1.5 times greater for light compared to heavy grazing. Total C (litter + root) contribution for perennial grasses was 2.7 times greater than that for triticale. Perennial grasses provided a larger litter base and root system that promote greater storage of C in the soil compared with triticale.
    • Grazing impacts on litter and soil organic matter in mixed prairie and fescue grassland ecosystems of Alberta

      Naeth, M. A.; Bailey, A. W.; Pluth, D. J.; Chanasyk, D. S.; Hardin, R. T. (Society for Range Management, 1991-01-01)
      Impacts of long-term cattle grazing on litter and soil organic matter were assessed in mixed prairie, parkland fescue, and foothills fescue grasslands of Alberta, Canada. Grazing regimes were of light to very heavy intensities, grazed early, late, and continuously during the growing season. Litter and soil organic matter were sampled in 0.1-m2 quadrats and removed as live vegetation, standing litter, fallen litter, and soil organic matter. Litter and organic matter samples were air dried and sorted by size using sieves and an automatic sieve shaker. Organic carbon content was determined by thermal oxidation. Ground cover was determined using point frames, and heights of standing litter and fallen litter were measured. Heavy intensity and/or early season grazing had greater negative impacts on litter and soil organic matter than did light intensity and/or late season grazing. Under the former regimes there were significant reductions in heights of standing and fallen litter, decreases in live vegetative cover and organic matter mass, and increases in bare ground. More large particle-sized organic matter, particularly standing litter, occurred in controls than in grazed treatments since it would not be removed or trampled by grazing animals. More medium and small particle-sized organic matter occurred in grazed treatments than in ungrazed controls since vegetation likely decomposed more rapidly when it was trampled and broken down as animals grazed.
    • Grazing impacts on selected soil parameters under short-term forage sequences

      Mapfumo, E.; Chanasyk, D. S.; Baron, V. S.; Naeth, M. A. (Society for Range Management, 2000-09-01)
      Long-term cultivation is known to change soil physical and chemical properties, but little is known about whether short-term agricultural practices, such as rotational grazing, can initiate such changes. This study investigated the impacts of 3 grazing intensities (heavy, medium, and light) and 4 forages on selected soil physical and chemical parameters of a Typic Haplustoll at Lacombe, Alberta. Measurements were conducted on soil samples collected at the beginning (1993) and the end (1996) of the study. Two perennial forages, smooth bromegrass (Bromus inermis cv. 'Carlton') and meadow bromegrass (Bromus riparius cv. 'Paddock'), and 2 annuals, a mixture of triticale (X Triticosecale Wittmack cv. 'Pika') and barley (Hordeum vulgare L. cv. 'AC Lacombe') and triticale alone were used for the study. Grazing intensity or forage species did not affect carbon-to-nitrogen ratio. Grazing intensity influenced changes in available water holding capacity for the 0-5 cm interval, soil nitrogen for the 30-45 cm interval, soil pH for the 5-15 cm interval and electrical conductivity for all depth intervals except for the 0-5 cm interval (P less than or equal to 0.05). Forage species affected changes in soil carbon in the 0-5 cm interval, soil pH between 0 and 15 cm, and electrical conductivity between 5 and 45 cm (P less than or equal to 0.05). Soil electrical conductivities for all grazing levels and forage treatments were within the range (i.e. 0-2 dS m-1) considered to have negligible effects on plant growth. The minimal effects of grazing and plant species on soil parameters in this study may have been due to the resilient intrinsic properties of the soil and/or the short study length.
    • Grazing impacts on soil nitrogen and phosphorus under Parkland pastures

      Baron, V. S.; Dick, A. C.; Mapfumo, E.; Malhi, S. S.; Naeth, M. A.; Chanasyk, D. S. (Society for Range Management, 2001-11-01)
      Because intensive grazing is new to the humid western Canadian parkland (prairies), there is little information available about its effects on soil N and P status. This study addressed the question of grazing intensity and pasture species effects on soil macronutrient status in a Typic Haplustoll at Lacombe, Alberta. Paddocks of smooth bromegrass (Bromus inermis Leyss.), meadow bromegrass (Bromus riparius Rhem.), and winter triticale (X Triticosecale Wittmack.), replicated 4 times, were subjected to 3 grazing intensities (heavy, medium, and light as defined by frequency and severity of defoliation) using yearling beef heifers. Nitrogen (N), P and K fertilisers were broadcast annually at 100, 22 and 42 kg ha(-1) during production years. The experiment was maintained on the same paddocks for 4 years. In the establishment year and in the third and fourth production years, soil samples were taken randomly from each paddock to a depth of 60 cm. Concentrations of nitrate-N (NO3-N), ammonium-N (NH4-N), mineral-N (the sum of NO3-N and NH4-N), total Kjeldahl-N, and extractable-P were determined in the 0-15, 15-30, 30-60, and 0-60-cm depths. Nitrate-N concentration was (1.7 to 2.4 times) greater for heavy than light grazed treatments for each soil depth increment and the amount of NO3-N in the 0-60 cm depth was 2.2 times greater than light paddocks. More NO3-N was measured under perennials than triticale (22.2 vs 13.6 mg kg(-1), respectively) at the 30-60-cm depth. Ammonium-N amount (0-60 cm) was greater in meadow bromegrass (30 kg ha(-1)) than in triticale (25 kg ha(-1)), but not smooth bromegrass paddocks for the 0-15-cm depth. Extractable-P concentration was greater in the 0-15-cm depth of heavy (154 mg kg(-1)) than in medium (138 mg kg(-1)) or light-grazed (127 mg kg(-1)) paddocks and was higher under meadow bromegrass than under triticale. Given the large amounts of NO3-N in the heavy paddocks, there is potential for loss through both leaching and denitrification. Differences among treatments for NH4-N, and P concentrations are not of particular concern environmentally, but are important from a fertility management point of view.
    • Grazing intensity impacts on pasture carbon and nitrogen flow

      Baron, V. S.; Mapfumo, E.; Dick, A. C.; Naeth, M. A.; Okine, E. K.; Chanasyk, D. S. (Society for Range Management, 2002-11-01)
      There is little information on the impact of grazing intensity on productivity and sustainability of intensively managed pastures in the humid, short-season parkland of the Canadian prairies. Our hypothesis was that above-ground productivity of dry matter, carbon, nitrogen, and in vitro digestible organic matter would be reduced proportionately with increasing grazing intensity. The study was conducted on a Typic Haplustoll at Lacombe, Alberta. Paddocks of meadow bromegrass (Bromus riparius Rhem.), replicated 4 times, were subjected to heavy, medium and light grazing intensities. Measurements and analyses were carried out for 3 years. Yields of dry matter, carbon, nitrogen, and in vitro digestible organic matter before and after grazing were determined and seasonal pools of above ground production, disappearance and residual were calculated. Concentrations of acid and neutral detergent fiber and lignin were also determined before and after grazing. Increasing grazing intensity tended to increase nitrogen and decrease fiber concentrations for available and residual forage. Heavy and medium grazing intensities produced 83 and 90% as much above ground dry matter and 87 and 90% above ground carbon as the light intensity. All disappearance pools were similar among grazing intensities except in vitro digestible organic matter, where heavy was 116% of light. Heavy grazing reduced the contribution of vegetative dry matter, in vitro digestible organic matter, carbon and nitrogen to the residual to 41, 50, 36, and 52% of that for light grazing. Adding estimated fecal-carbon to the residual significantly increased total residual carbon. Estimated fecal-carbon represented 68, 51, and 42% of all carbon inputs to litter for heavy, medium and light grazing, respectively. Grazing intensity did not affect estimated pools of excreted nitrogen, but increased estimated precent of nitrogen excreted as urine.
    • Water holding capacity of litter and soil organic matter in mixed prairie and fescue grassland ecosystems of Alberta

      Naeth, M. A.; Bailey, A. W.; Chanasyk, D. S.; Pluth, D. J. (Society for Range Management, 1991-01-01)
      Litter and organic matter accumulations can reduce soil water through interception of precipitation and subsequent evaporation of absorbed water. Interception varies with mass and water holding capacity (WHC) of litter and organic matter, and is highest from small precipitation events. WHC varies with vegetation type, which is affected by grazing regime. Thus long-term grazing could affect WHC of litter and organic matter and would be important in the hydrologic assessment of rangelands subjected to many small precipitation events throughout the growing season. The study was conducted in mixed prairie, parkland fescue, and foothills fescue grasslands in Alberta, Canada. Grazing regimes were of light to very heavy intensities, grazed early, late, and continuously during the growing season. Litter and organic matter were sorted by sieving into various sized categories. Litter-soil cores were also evaluated. WHC of litter and organic matter was lower in mixed prairie than in fescue grasslands. WHC increased with increazed particle size, being higher for roots and standing and fallen litter than for organic matter. WHC of large particle-sized material decreased with heavy intensity and/or early season grazing. WHC was affected more by intensity than season of grazing. Grazing affected WHC through species composition changes, since species have different WHC, and through trampling which affected particle size. It was concluded that litter and organic matter WHC were important in rangeland hydrologic assessments.