Distribution of Event Mean Concentration (EMC) of Nitrogen and Phosphorous from a Combined Dairy and Crop Farming Watershed

摘要

Event mean concentration (EMC) of Nitrogen (N) and Phosphorus(P) is primary information for nonpoint source pollution assessment of a watershed. EMCs for various types of agriculture such as dairy, row crop farming under different climate and geologicconditions are not fully developed, yet. An agricultural watershed in Piedmont region in Maryland has been monitored for 10 years as a section 319 national monitoring program. Dairy manure was the main source of fertilizer for crop farming in this watershed. Observed mean concentrations of N and P for each event were analyzed. Distribution of EMCs for N and P showed wide range of variations. Representative EMCs of T-N and NO3-N from combined dairy and crop farming tend to be higher than those reportedfor agricultural watershed. This study confirmed that site-specific EMC information ? for various agricultural practices are required for better assessment of nonpoint source pollution using EMC method.