Flow volumes and NO 3 -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 NO 3 -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 NO 3 -N concentrations ranged from 1 to 65 mg L" 1 and there were substantial changes in NO 3 -N concentrations within flow events. The flow-weighted average annual nitrate concentrations of the drainage effluent, (NO 3 -N)|,, were > 10 mg L ' for potato site-years, regardless of whether the sites were established potato rotation fields or not. The (NO 3 -N)J concentrations of the established potato rotation sites also remained >10 mg L ' for the first non-potato year following potato. The (NO 3 -N)£ 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 NO 3 -N leaching for the potato site-years for the measured April to December periods ranged from 5 to 33 kg N ha '. More work, under controlled conditions, is required to determine both dormant and growing season NO 3 -N leaching associated with various potato production systems.
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