Reducing Nutrients Through Conservation: A Paired Watershed Study.

The Jordan Lake watershed is a regulated, nutrient-impaired watershed in North Carolina’s piedmont region.  All sectors, point and nonpoint source (agriculture and urban) are expected to reduce nitrogen (N) and (P) loads to the lake.  The objective of this study is to quantify the effectiveness of agricultural best management practices (BMPs), such as livestock exclusion and nutrient management for pastures and nutrient management for cropland. We have used a paired watershed water quality design (2 predominantly pasture and 2 predominantly cropland watersheds). For each watershed, rainfall and discharge are monitored continuously and storm-event, flow-proportional samples are collected and analyzed for total P, dissolved P, total Kjeldahl N, ammonia N, total N, nitrate-N and sediment in order to compare pollutant export. In addition to surface water quality monitoring, agricultural production activities, such as fertilizer application, tillage, animal stocking density, and crops are collected yearly for each watershed. Livestock exclusion fencing and nutrient management were implemented in October 2011 in one of the paired pasture watersheds after 1.5 years of continuous water quality monitoring. Nutrient management was implemented this growing season (2013) in one of the paired cropland watersheds, as the calibration period just finished. Preliminary monitoring data for the pasture treatment watershed suggests a reduction of phosphorus, nitrogen, and sediment exports since the implementation of the BMPs.