Browsing Journal of Range Management, Volume 46, Number 5 (September 1993) by Subjects
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Research Observation: Chemical repellants to reduce grazing intensity on reclaimed sitesRevegetation of disturbed rangelands in western Canada is severely impeded by cattle grazing. Fencing to protect emergent vegetation is costly and restricts animal movement. Chemically repelling cattle from emergent vegetation may provide a convenient and economical alternative to fencing. This study determined whether certain repellents could reduce grazing intensity on vegetation to which they were applied compared to untreated vegetation. Canopy measurements were used to compare grazing intensity. Three trials were conducted on reclaimed land within the Aspen Parkland region of central Alberta. Time since reclamation was over 10 years in Trial A, 2 years in Trial B, and 3 weeks in Trial C. Pregnant mares' urine, Hinder® (150 mg ml-1 ammonium soaps), Skoot® (120 mg mi-1 tetramethylthiuram disulfide), and Deer-Away Big Game Repellent® (37% putrescent egg solids) were evaluated. Two concentrations of each repellent were sprayed onto 1 X 3-m treatment plots randomized within blocks replicated 4 to 6 times. Plot canopies were measured either by gently resting a sheet of plastic laminate over the canopy, or by lowering a sliding bar attached perpendicularly to a meter stick until it contacted the uppermost leaves of the canopy, and recording the height of the sheet or bar above the soil surface. Canopies of plots treated with Big Game Repellent® were taller than control plot canopies on each measurement date in all trials, indicating grazing was reduced. Big Game Repellent® plots were also generally taller than plots treated with other repellents. Canopies of plots treated with pregnant mares' urine, Hinder®, and Skoot® generally did not differ from control plots, nor did they differ from each other in any trial. Low repellent concentrations did not reduce grazing in any trial, but high concentrations reduced grazing in all trials. Repellent effectiveness was not permanent since all canopy measurements became shorter with time. Big Game Repellent® was effective in reducing grazing intensity by cattle, but practical use of repellents for grazing management requires further investigation.
Soil water extraction and photosynthesis in Gutierrezia sarothrae and Sporobolus cryptandrusBroom snakeweed (Gutierrezia sarothrae Shinners), a C3 evergreen half-shrub, is a formidable competitor of grasses in the semiarid southwestern rangelands. Sand dropseed (Sporobolus cryptandrus (Toff.) Gray), perennial C4 bunchgrass, is the most drought resistant species in the short-grass prairie. A comparative study on soil water extraction patterns, photosynthesis, and canopy development in both species during spring-summer growing season of 1991 was conducted in pot- and field-grown plants. Sand dropseed extracts water at depths between 0 and 30 cm more effectively than broom snakeweed. In contrast, broom snakeweed can take up more water from the subsoil (30-60 cm) than sand dropseed. Photosynthesis in sand dropseed was more affected by soil water deficit than was broom snakeweed, which was related to their water extraction patterns. Leaf area accumulation of broom snakeweed was not affected by spring drought, but that of sand dropseed was reduced. Because of greater water extraction from the wetter subsoil by broom snakeweed during drought, it can assimilate more carbon and, therefore, prevail in a competitive relationship with sand dropseed.