Agricultural practices for cleaner water: a global synthesis of meta-evidence
Canning, Adam D. (2026) Agricultural practices for cleaner water: a global synthesis of meta-evidence. Environmental Reviews, 34.
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Abstract
Agricultural intensification has pushed nitrogen and phosphorus cycles beyond safe planetary limits, with agriculture now a primary driver of at least two Earth system boundaries being breached. Technological fixes alone are unlikely to resolve this: efficiency gains tend to lower production costs and drive further expansion (known as Jevon’s Paradox), intensifying environmental pressure rather than relieving it. Reducing agricultural water pollution will therefore require a shift toward production systems that work with ecological processes rather than against them. Despite growing interest in agroecological and regenerative approaches, evidence on their effectiveness for improving water quality remains fragmented across practices, regions, and study designs. This review of review synthesizes global evidence from 67 multi-continental meta-analyses on how farm practices affect nutrient, pesticide, and sediment losses. Nonlegume cover crops cut nitrate leaching by about 50%–70% and sediment by 50%–60%. Residue retention and organic amendments reduced runoff nutrients by 25%–50% and sediment by up to 75%. Reduced tillage lowered sediment losses by about 60% but often increased nitrate leaching, highlighting the importance of complementary fertilizer management. Optimizing fertilizer rates, timing, and formulation, alongside precision irrigation, reduced nitrogen losses by 20%–70%. At the landscape scale, vegetated buffers, agroforestry, and wetlands typically removed 25%–90% of nutrients and 40%–95% of sediment. Improving soil cover, structure, and hydrological function can sharply reduce pollution without sacrificing yields, showing that poor water quality stems from management, not inevitability. However, important evidence gaps remain: pesticide transport lacks any global synthesis despite residues being among the most pervasive agricultural contaminants, quantitative evidence on adaptive grazing management remains limited, and most underlying studies are concentrated in temperate croplands of North America, Europe, and China, limiting confidence in applying these findings to tropical, arid, or smallholder systems.
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