Soil acidification and the importance of liming agricultural soils with particular reference to the United Kingdom

• Published in: Soil use and management Vol. 32; no. 3; pp. 390 - 399
• Main Author: Goulding, K. W. T.
• Format: Journal Article
• Language: English
• Published: England Blackwell Publishing Ltd 01.09.2016; Wiley Subscription Services, Inc; John Wiley and Sons Inc
• Subjects: Acid deposition; Acidification; Acidity; Agricultural land; Agricultural production; agricultural soils; Aluminum; ammonia; Ammonium; carbon dioxide; Carbon dioxide emissions; Cation exchange; cation exchange capacity; Cation exchanging; Cations; chemical bases; clay; Crop yield; crops; Farming; farming systems; Farms; fertilizer; Fertilizers; gases; grassland soils; Grasslands; greenhouse gas emissions; Land; legumes; Lime; lime requirement; Liming; liming materials; neutralization; Nitric acid; Nitrous oxide; nutrients; Review; Soil (material); Soil acidification; Soil pH; Soil Physico‐chemical Properties and Their Management; Soil quality; Soils; Sulfur dioxide; sulfur fertilizers; United Kingdom; Urea; urea fertilizers; British Isles; United Kingdom; soil acidification; Acid deposition; liming; fertilizer; lime requirement
• ISSN: 0266-0032; 1475-2743
• DOI: 10.1111/sum.12270

Soil acidification is caused by a number of factors including acidic precipitation and the deposition from the atmosphere of acidifying gases or particles, such as sulphur dioxide, ammonia and nitric acid. The most important causes of soil acidification on agricultural land, however, are the application of ammonium‐based fertilizers and urea, elemental S fertilizer and the growth of legumes. Acidification causes the loss of base cations, an increase in aluminium saturation and a decline in crop yields; severe acidification can cause nonreversible clay mineral dissolution and a reduction in cation exchange capacity, accompanied by structural deterioration. Soil acidity is ameliorated by applying lime or other acid‐neutralizing materials. ‘Liming’ also reduces N2O emissions, but this is more than offset by CO2 emissions from the lime as it neutralizes acidity. Because crop plants vary in their tolerance to acidity and plant nutrients have different optimal pH ranges, target soil pH values in the UK are set at 6.5 (5.8 in peaty soils) for cropped land and 6.0 (5.3 in peaty soils) for grassland. Agricultural lime products can be sold as ‘EC Fertiliser Liming Materials’ but, although vital for soil quality and agricultural production, liming tends to be strongly influenced by the economics of farming. Consequently, much less lime is being applied in the UK than required, and many arable and grassland soils are below optimum pH.