Do increased stocking periods affect weed population in pastures in Southern Wisconsin?

Authors: DUARTE, ARTHUR - University Of Wisconsin; RENZ, MARK - University Of Wisconsin; KOHMANN, MARTA - University Of Wisconsin; Jaramillo, David

Submitted to: North Central Weed Science Society US Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/12/2023
Publication Date: 12/12/2023
Citation: Duarte, A., Renz, M., Kohmann, M., Jaramillo, D.M. 2023. Do increased stocking periods affect weed population in pastures in Southern Wisconsin?. North Central Weed Science Society US Proceedings. Dec. 11-14, 2023. Minneapolis, MN.

Interpretive Summary:

Technical Abstract: Rotational stocking is an effective management strategy to increase pasture and animal productivity. An additional benefit to this system is reduced weed populations. The frequency of rotation, however, is not uniformly applied throughout the midwestern United States with producers common stocking periods ranging from daily to weekly. These differences not only have the potential to affect productivity of pastures and animals but also could influence weed populations. We conducted an experiment in 2023 at the Lancaster Agricultural Research Station, near Lancaster, WI. The area is a cool season grass-legume pasture composed of white clover (Trifolium pratense L.), red clover (Trifolium pratense L.), orchardgrass (Dactylis glomerata L.), smooth brome (Bromus inermis Leyss.), quackgrass (Elymus repens L. Gould), and tall fescue (Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.). Common weed species were dandelion (Taraxacum officinale Weber ex Wigg.), Canada thistle (Cirsium arvense (L.) Scop.), broadleaf plantain (Plantago major L.), and yellow foxtail (Setaria pumila (Poir.) Roem. & Schult). The study was arranged in a randomized complete block design with three replicates where we tested three different stocking periods. Angus and Holstein/Angus cattle were placed in plots for either 1, 4 or 8 d before being rotated to another paddock. Each paddock was then allowed to regrow for 32 days before the next grazing event. Stocking rate was determined based on forage allowance and stocking period for each treatment. Four grazing events occurred throughout the season between June and September. Plant responses assessed included productivity throughout the grazing season, biomass of plants prior to each grazing event, and point intercept transects in fall to evaluate cover. The data was analyzed in R with analysis of variance and means were separated using the Least Significant Difference (LSD) test. Weed biomass was minimal and similar across treatments prior to the first and second grazing event. Increases in weed biomass was detected at the third grazing event with two and eleven-fold more than the 4 or 8 d stocking period (P<0.01). Despite this difference the overall weed biomass (246 g m-2) over the grazing season and fall cover (18%) did not differ. Animal behavior may be a reason for these differences and 8 d stocking periods had increased trampling, soil disturbance, manure, and more selective grazing than 1 or 4 d periods. Forage regrowth was limited due to a drought between the second and third grazing event. This may have increased weed biomass and amplified differences among treatments. This experiment will be continued in 2024 to evaluate the long-term effects of stocking period on weed populations and livestock performance. These findings will contribute to the development of improved practices for weed management on rotationally stocked pastures.