Tile drainage waters from five systematically tiled, commercial potato fields in northwestern New Brunswick were analyzed for the herbicides metribuzin and dinoseb from April 1987 to April 1989. Tile drain outflow rate and volume were also recorded. Dinoseb and metribuzin were detected in tile outflow both during the year of application and during the subsequent spring melt period, but at concentrations substantially less than maximum acceptable concentrations (MAC) for drinking water published by Health and Welfare Canada. Average concentrations of dinoseb twelve months after application ranged from less than the detection limit to 0.21-mu-g.L-1 (five site-years), and the concentration of metribuzin ten months after application averaged 0.22-mu-g.L-1 (one site-year). Persistence of dinoseb in the tile outflow did not appear to be affected by the history of dinoseb use other than those applications occurring within the past 12 months.

Milbum, P., O'Neill, H., Gartley, C, Pollock, T., Richards, J.E. and Bailey, H. 1991. Leaching of dinoseb andmetribuzin from potato fields in New Brunswick. Can.Agric.Eng.33:197-204. Tiledrainage waters from five systematically tiled, commercial potato fields in northwestern New Brunswick were analyzed for the herbicides metribuzin and dinoseb from April 1987 to April 1989. Tile drain outflowrate and volume were also recorded. Dinoseb and metribuzin were detected in tile outflow both during the year of application and during the subsequent spring melt period, but at concentrations sub stantially less than maximum acceptable concentrations (MAC) for drinking water published by Health and Welfare Canada. Average concentrationsof dinoseb twelve months after application ranged from less than the detection limit to 0.21 Jig-L"1 (five site-years), and the concentration of metribuzin ten months after application averaged 0.22 M-g'L"1 (one site-year). Persistence ofdinoseb inthe tile outflow did notappear tobe affected bythehistory of dinoseb use other than those applications occurring within thepast12months.

AbstractFlow volumes and NO3‐N concentrations of drain discharge from five systematically tiled, commercial potato (Solatium tuberosum L.) fields were measured from April to December, 1987 and 1988, to assess the potential for NO3‐N leaching associated with current production practices. The sites, located in New Brunswick, Canada, ranged from 3 to 10 ha and varied in fertilizer application rate, cropping practices, rainfall, and duration of data collection (the latter due to site access difficulties in the spring). Three of the five sites were representative of intense potato rotations, whereas the remaining two were representative of land conversions into potato production from more passive, low input production systems. Ten site‐years of data were collected. Drain outflow volumes averaged 75 and 115 mm per unit area in 1987 and 1988, respectively. Considerable drain flow occurred during snowmelt each year before data collection began. Measured NO3‐N concentrations ranged from 1 to 65 mg L−1 and there were substantial changes in NO3‐N concentrations within flow events. The flow‐weighted average annual nitrate concentrations of the drainage effluent, , were ≥ 10 mg L−1 for potato site‐years, regardless of whether the sites were established potato rotation fields or not. The concentrations of the established potato rotation sites also remained > 10 mg L−1 for the first non‐potato year following potato. The concentration of one potato rotation site was more than double that of the other two potato rotation sites. Incubation studies showed the soil at this site had considerably more potential to mineralize N than the other two sites. Total NO3‐N leaching for the potato site‐years for the measured April to December periods ranged from 5 to 33 kg N ha−1. More work, under controlled conditions, is required to determine both dormant and growing season NO3‐N leaching associated with various potato production systems.