, Volume 64, Issue 3, pp 237-256

Nitrate leaching in temperate agroecosystems: sources, factors and mitigating strategies

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Abstract

Nitrate (NO3 ) leaching from agriculturalproduction systems is blamed for the rising concentrations ofNO3 in ground- and surface-waters around the world.This paper reviews the evidence of NO3 leachinglosses from various land use systems, including cut grassland, grazed pastures,arable cropping, mixed cropping with pasture leys, organic farming,horticultural systems, and forest ecosystems. Soil, climatic and managementfactors which affect NO3 leaching are discussed.Nitrate leaching occurs when there is an accumulation ofNO3 in the soil profile that coincides with or isfollowed by a period of high drainage. Therefore, excessive nitrogen (N)fertilizer or waste effluent application rates or N applications at the wrongtime (e.g. late autumn) of the year, ploughing pasture leys early in the autumn,or long periods of fallow ground, can all potentially lead to highNO3 leaching losses. N returns in animal urine havea major impact on NO3 leaching in grazed pastures.Of the land use systems considered in this paper, the potential for causingNO3 leaching typically follow the order: forest< cut grassland < grazed pastures, arable cropping < ploughing ofpasture < market gardens. A range ofmanagement options to mitigate NO3 leaching isdescribed, including reducing N application rates, synchronizing N supply toplant demand, use of cover crops, better timing of ploughing pasture leys,improved stock management, precision farming, and regulatory measures. This isfollowed by a discussion of future research needs to improve our ability topredict and mitigate NO3 leaching.