A comparison of stocking method effects on surface runoff quantity and quality is ongoing. The stocking methods to be evaluated are 1) continuous stocking, 2) rotational stocking, and 3) mob stocking. Water quantity and quality data from runoff induced by rainfall simulation have been collected over two grazing seasons (2012 and 2013). A total of 99 rainfall simulations have been performed. Stocking method impacts on runoff quantity and nutrient losses were minimal in 2012. Stocking density of the mob stocking treatment was increased in 2013. Additionally, improvements to the data collection protocol were made for data collected in 2013. During 2014, data from 2013 will be analyzed and water quantity and quality data will be collected for a third year of the study.
1. Compare runoff volumes among mob, rotationally, and continuously stocked pastures.
2. Compare sediment losses in runoff among mob, rotationally, and continuously stocked pastures.
3. Compare nutrient losses in runoff from mob, rotationally, and continuously stocked pastures.
Sixty-three simulated runoff events were induced by rainfall simulation during the 2012 grazing season. 10 runoff events occurred prior to stocking and 53 runoff events were performed post-stocking. Water quality analysis has been completed for four subsamples (timed at 10 minute intervals after initiation of runoff) for each runoff event. Water quantity and quality data from 2012 has been analyzed for stocking method effect. A Master’s thesis was published based on the data collected in 2012. Thirty-six runoff events (9 pre-stocking and 27 post-stocking) were induced by rainfall simulation during the 2013 grazing season. Water quantity and quality data were collected for each event.
This research will provide a comparison of the effects on runoff quantity and quality of mob stocking to other stocking methods. In the end, this research will be utilized by USDA-ARS to develop protocols and tools for field data collection in order to classify ecological response units as defined by the Pastureland Conservation Effects Assessment Project (CEAP). Data from these initiatives will be used by CEAP to develop and refine models such as the Soil and Water Assessment Tool (SWAT) to provide information on the water quality benefits of pastureland conservation practices at larger scales. The proposed work is a joint effort with USDA
ARS scientists to develop a regionally-based understanding of nutrient transport and fate in pasture-based systems relative to implementation of conservation practices.