| Tile-drainage systems assist in the transport of nutrients from soils to surface waters, where enrichment may promote eutrophication through accelerated algae growth. Phosphorus (P) and nitrate (NO3 --N) concentrations were monitored weekly in tile-drainage from 39 agricultural fields in Nova Scotia, Canada. Generally, soil test P (STP) levels exceeding 190 mg P kg-1 produced higher drainage water P and NO3--N concentrations. Some soils with lower STP (<80 mg P kg-1) exceeded standards. Although variable, total P (TP) concentrations increased with flow rate at 73% of the fields. Flow rate and NO3--N had an inverse relationship. Water pH remained consistent and could not be correlated to concentration changes. Leaching was most variable during April-May, and October-November, apparently impacted by field activity and large drainage events. Site mean (n=39) and sample TP (n=1358) concentrations exceeded the USEPA standard (0.10 mg TP L-1) at a frequency of 82% and 29%, respectively. |
