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Animal Industry Report

Extension Number

ASL R2530

Topic

Environment

Summary and Implications

Grazing management practices in pastures can affect the sward and physical characteristics of riparian areas near pasture streams. These areas are prone to sediment, phosphorus, and fecal pathogen loading via surface run-off into the streams causing non-point source pollution of water sources. Six cool-season grass pastures were grazed by continuous stocking with unrestricted stream access (CSU), continuous stocking with access to the stream restricted to a 16-foot wide stabilized stream crossing (CSR), or rotational stocking (RS). For data and sample collections, pastures were divided into 2 zones: on the streambank (streambank zone) and 0 to 110 feet from the streambank (110 zone). Forage heights were measured and forage samples were collected from congregation and open areas in each zone to determine forage mass monthly from May to October. The percentages of bare and fecal-covered ground were also measured monthly at each sampling site. Simulated rainfall was applied on bare and vegetated areas on the streambanks of the pastures and the runoff was collected and measured to determine the amounts of total run-off and transport of sediment, phosphorus, and fecal pathogens. Forage height in the streambank and 110 zones was greater in CSR pastures than CSU pastures from July through October and June through October, respectively (P < 0.10). Likewise, CSR pastures maintained greater forage mass than CSU pastures in the streambank and 110 zones from September through October and July through October, respectively. Fecal ground cover was greater in the streambank and 110 zones in CSU and RS pastures than CSR pastures in June and October, and September, respectively (P < 0.10). Bare ground cover in the streambank zone was greater (P < 0.10) in CSU pastures than in CSR and RS pastures in September and October and in the 110 zone from July through September. The percentage of run-off from rainfall simulations and the amounts of total P transported in precipitation runoff were greater from bare ground than vegetated ground along streambanks across grazing treatments (P < 0.05).

Copyright Holder

Iowa State University

Language

en

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