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Pasture Management Effects on Nonpoint Source Pollution of Midwestern Watersheds

Russell, James
Iowa State University
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End date
The long-term goal of this program is to demonstrate reduced sediment, phosphorus, and pathogen loading into surface water resources as a result of implementation of cost-effective grazing management and/or pasture improvement practices that alter the timing, frequency, duration and/or intensity of cattle grazing near pasture streams.

In order to encourage cattle producers to implement these changes, the research objectives of the project are:

  1. Quantify the effects of pasture management on potential sediment and phosphorus loading of surface water resources from stream bank erosion and manure deposition in Iowa watersheds;
  2. Evaluate the effects of botanical composition, grazing management, and climatic conditions in pastures on the temporal and spatial distribution of cows grazing within and outside riparian zones of Midwestern pastures. The education objective is to introduce undergraduate and graduate students to principles and practices of managing livestock in confinement and grazing production systems to minimize adverse effects on ecosystems and the methods to monitor these effects through a world wide web-based course.
The extension objectives are:
  1. Demonstrate the effects of improved management practices on erosion and manure deposition on stream banks in pastures on farms in the Rathbun Lake watershed in southern Iowa and Willow Creek sub-watershed in central Iowa;
  2. Prepare and distribute a highly illustrated, all-color publication for cattle producers describing cost-effective management practices to reduce nonpoint source pollution of pasture streams in Midwestern watersheds.
More information
Non-Technical Summary: While cropland dominates most watersheds in the Midwest, large portions of land in Midwestern watersheds, such as those in southern Iowa, are utilized as pastures. Previous studies have suggested that stream bank erosion and manure deposition from pastureland are major contributors to sediment and phosphorus loading of Iowa streams and lakes. These problems are likely related to poor grazing management and/or pasture conditions that promote frequent congregation of grazing cattle in or near pasture streams. The purpose of this project is to determine the efficacy of cost-effective grazing management and/or pasture management practices such as adjusting stocking rates, use of improved forage species, use of rotational grazing, use of stabilized crossings and providing off-stream water or shade in reducing sediment, phosphorus, and pathogen loading of surface water resources in Midwestern pastures.

Approach: Research objective 1: At least 12 beef cow-calf producers in the Rathbun Lake watershed whose pastures contain continuous-flowing streams will be identified as cooperators. In addition, six 12.1-ha pastures bisected by Willow Creek have been prepared to be grazed by continuous stocking with full access to the stream, continuous stocking with stream access limited to stabilized crossings, or rotational stocking with stream access only in the riparian paddock. In 2006, 1.6 x 76.2 cm fiberglass erosion pins will be placed at 1 m intervals from the base to the top of each bank along a minimum of 10 equidistant transects in each pasture and in at least two sites in which cattle access is prevented. The length of exposed pins will be measured monthly from May through October of 2007, 2008 and 2009 for measurement of soil erosion/deposition activity. In addition, soil erosion will be measured at the Willow Creek site using ground-based LIDAR and image analysis of channel cross section photographs. Soil samples will be collected in the spring of each year for determination of bulk density and phosphorus. The proportion of soil that is bare or manure-covered and forage sward height within 32.3 m of the stream will be measured monthly. Ambient temperature, humidity, precipitation, and stream flow will also be measured with data loggers. Research objective 2: In May, July, and September of 2007 through 2009, three cows in the herds of a minimum of 6 cow-calf producers in the Rathbun Lake watershed will be fitted with GPS collars and monitored for position at 10 minute intervals for 14 days. Simultaneously, pasture forage species and sward height, shade area, availability of shade, temperature, and humidity will be measured and mapped in riparian and upland areas to relate cattle distribution to climatic and pasture conditions. GPS collars will also be placed on one cow for 14 days monthly in each of the six pastures along Willow Creek in research objective 1 to the temporal and spatial distribution of cattle. During the last 7 days of this period, cattle will have access to alternate water sources placed a minimum of 242 m on either side of the stream to determine their effects on cattle behavior. Education objective: A world wide web-based course entitled Livestock and the Environment will be developed for senior undergraduate and Masters level students. The course will have both lecture and laboratory sections and will cover nutrient balance in crop and livestock systems and the effects of grazing management on riparian ecosystems. Extension objective 1: Annual field days will be conducted at the sites involved in research objectives 1 and 2. In the winter 2008-09, participants at the field days will be surveyed to determine the effectiveness of the outreach program to improve water quality and identify impediments for producers to improve water quality. Extension objective 2: Prepare and distribute a six page, full color publication entitled Pasture Management to Improve Stream Water Quality covering topics including water quality concerns, flash grazing, alternative water, alternative shade, and economic considerations.

Funding Source
Nat'l. Inst. of Food and Agriculture
Project source
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Sanitation and Quality Standards
Bacterial Pathogens