Controlled grazing on annual grassland decreases yellow starthistle
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Authors: C. D. Thomsen, W. A. Williams, M. Vayssieres, F. L. Bell, and M. R. George
Date: 1993
Journal: California Agriculture
Volume: 47
Number: 6
Pages: 36-40
Summary of Methods: The effect of cattle, and sheep and goat grazing (2 years sheep followed by 1 year of goat grazing) on yellow starthistle was examined on two sites in California over three years. One site was located 20 miles west of Maxwell, CA while the second site was at the UC Davis Agronomy Farm. Cattle were grazed in a short duration, high intensity grazing system for three years at first site. Sheep were grazed for two years followed by goat grazing during the third year at the UC Davis Agronomy Farm in a short duration, high intensity grazing system. Grazing occurred at either rosette or bolt (pre-spiny) stages. Stocking rates for the cattle grazing site were 18 cow/calf pairs per 1/2 acre with grazing time periods ranging from less than 8 to 24 hours and were considered heavy grazing intensity. Stocking rates for the sheep grazing site were 20-40 ewes per 0.1 acre with grazing time periods of 2.5-3 weeks. Vegetative measurements were taken before and after grazing occurred.
Article Summary / Main Points: Cattle grazing caused minimal plant mortality, though canopy densities decreased by 90% and flowerhead densities also decreased. A 2 to 3 week window between grazing rotations is required to achieve the best control of yellow starthistle with cattle. Repeated sheep grazing prior to flowering did not decrease flowerhead densities (thought to be due to increased branching though it was not measured). The most significant effect following goat grazing, where a decrease of 239 flowerheads per square meter from the 2nd to the 3rd year of treatment. Closely managed repeated grazing periods during the bolt stage is the most effective way to control yellow starthistle as timing of grazing is more important that class of livestock. The number of required grazing periods is dependent upon spring rains, as increased spring rains increase soil moisture the number of required grazing periods increases.
Vegetation Types: California Grasslands (including all annual grasslands) Intermountain Grasslands (includes Palouse Prairie and Canyon Grasslands) Oak Woodlands Ponderosa Pine Woodlands
MLRA Ecoregions: 17 Sacramento and San Joaquin Valleys
Agrovoc Control Words: Noxious weeds Rangelands Grazing
Article Review Type: Peer Reviewed
Article Type: Experimental Research
Keywords: centaurea solstitialis, multi-species grazing, weed management, short-duration grazing, time-controlled grazing
Annotation: This research is the continuation of the preliminary findings published under the title 'Managing yellow starthistle on rangeland.' Increased yellow starthistle invasion makes this research relevant to all.
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