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

TLDR: In this article, 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 are discussed.

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.