Nitrate leaching is the transport of nitrate ions beyond the root zone by percolating water, particularly in winter[1]. Not held by soil particles, the anion moves freely with water; even ammoniacal or amide nitrogen is quickly oxidised to nitrate by soil bacteria[2]. Any nitrogen source — mineral fertilisers, manures, organic matter — can produce this loss[1][2]. Over-application represents the main risk factor, whilst fertiliser use matched to crop requirements does not increase it[1]. In the EU, roughly 22 % of arable land overlies aquifers exceeding 20 mg of NO₃⁻ per litre[2].
Sources
- Yara, Fertilizer Industry Handbook 2025, p. 23 · View the source
- FAO, Plant nutrition for food security (2006), p. 320 · View the source
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Updated October 27, 2026