Long-term simulations of nitrate leaching from potato production systems in Prince Edward Island, Canada

LEACHN was employed to simulate nitrate leaching from a representative potato production system in Prince Edward Island (PEI), Canada and enhance the understanding of impacts of potato (Solanum tuberosum L.) production on groundwater quality. The model's performance on predicting drainage was examined against water table measurements through coupled LEACHN and MODFLOW modeling. LEACHN was calibrated and verified to data from tile-drain leaching experiments of potato grown in rotation with barley (Hordeum vulgare L.) and red clover (Trifolium pratense L.) during 1999-2008. Long-term simulations using the calibrated model were performed to evaluate the effects of climate and N fertilization for the potato crop on nitrate leaching. The modeling suggests LEACHN can be an effective tool for predicting nitrate leaching from similar cropping systems in PEI. Both measurements and simulations showed nitrate leaching primarily occurred during the non-growing season when crop uptake diminishes, and nitrate from mineralization and residual fertilizer coexists with excessive moisture from rainfall and snowmelt infiltration. Annual average nitrate leaching following potato, barley and red clover phases was predicted to be 81, 54 and 35 kg N ha-1, respectively, and the corresponding leached concentrations were 15.7, 10.1 and 7.3 mg N l-1. Increased N input for potato alone increased nitrate leaching not only during potato phase but also during the rotation crop phases. To reduce the risk of nitrate leaching, practices should be developed to minimize nitrate accumulation in soil both during and outside of the growing season and in both the potato and the rotation crop phases. © 2011 Springer Science+Business Media B.V.