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Title: IMPACT OF DIFFERENT GRAZING SYSTEMS AND VEGETATIVE FILTER STRIPS ON SEDIMENT AND NUTRIENT LOSSES WITH SURFACE RUNOFF

Author
item AHMED, S - IOWA STATE UNIV.
item MICKELSON, S - IOWA STATE UNIV.
item RUSSELL, J - IOWA STATE UNIV.
item POWERS, W - IOWA STATE UNIV.
item SCHULTZ, R - IOWA STATE UNIV.
item Kovar, John

Submitted to: Agricultural Engineering International Conference
Publication Type: Proceedings
Publication Acceptance Date: 7/31/2002
Publication Date: 7/31/2002
Citation: AHMED, S., MICKELSON, S.K., RUSSELL, J.R., POWERS, W.J., SCHULTZ, R.C., KOVAR, J.L. IMPACT OF DIFFERENT GRAZING SYSTEMS AND VEGETATIVE FILTER STRIPS ON SEDIMENT AND NUTRIENT LOSSES WITH SURFACE RUNOFF. AGRICULTURAL ENGINEERING INTERNATIONAL CONFERENCE PROCEEDINGS. 2002. PAPER NO. 022141.

Interpretive Summary: The amounts of sediment and phosphorus (P) in surface runoff from agricultural lands are of concern because of the potential for siltation and eutrophication of Iowa's waterways. Because of current problems, it is likely that the U.S. Environmental Protection Agency will implement regulations to control the total maximum daily loads of nutrients in watersheds in the near future. At this time, there is limited information on total sediment and P losses in runoff from pastureland in the Midwest. Because aboveground biomass limits soil disruption caused by the impact of raindrops and roots hold soil particles, forages harvested at an appropriate height through suitable grazing management should promote water infiltration and minimize sediment and P loss in runoff water from pastures. The objectives of this experiment are to quantify the amounts of sediment and P in surface runoff from pasturelands managed by different systems, develop tools to monitor and control sediment and P transport from pastures, and develop best management practices for producers to control sediment and P losses, while optimizing forage productivity. Early results indicate that by practicing good forage management techniques the amounts of sediment and nutrients coming off of pastureland can be controlled. Practices such as the use of buffer strips around waterways and rotational grazing of cattle can greatly reduce degradation of surface water resources. The results of this research will provide useful information to cattle producers, local environment groups, and Cooperative Extension and Natural Resources Conservation Service personnel.

Technical Abstract: The main objective of this research is to quantify the effect of grazing management practices and vegetative filter strips (VFS) on losses of total suspended solids (TSS), nitrate-nitrogen (NO3-N), ortho-phosphorus (PO4-P) and total P (TP) in surface runoff during natural rainfall events. The data is being collected during the 3-year study period (2001-2003) at the Iowa State Rhodes Farm, Iowa. Collection of runoff water for nine treatments with three replications is based on a total of 27 runoff plots, each 7.5' x 75'. Three grazing management practices (2" continuous grazing, 2" rotational grazing, and no grazing) and three VFS treatments (the area ratios of 5:1, 10:1, and no VFS) have been replicated three times in a randomized block design for statistical analysis purposes. The results of the study so far show that VFS removed significant quantities of TSS, NO3-N, PO4-P, and TP from surface runoff. In addition, the 5:1 area ratio is the most effective VFS for improving quality of runoff from grazing pastures. It can be clearly concluded from the study that grazing practices provide a potential for spatial and temporal variability of nutrient runoff from grazed pastures. Overall results of the study show that use of vegetative filter strips with rotational grazing has been found to be the most useful practice to reduce surface runoff contamination in both years of the study.