Soil Acidification Processes in Agroecosystems

Soil acidification in agricultural landscapes arises from the combined effects of intensive nitrogen fertilisation, acid deposition, crop uptake of basic cations and the subsequent leaching of protons and aluminium ions. Ammonium‐based fertilisers undergo microbial nitrification, releasing hydrogen ions that displace calcium, magnesium and potassium from exchange sites. Acid rain further accelerates proton input, while continuous cropping depletes buffering capacity by reducing organic matter and base saturation. Acidified soils show lower pH in surface horizons, elevated exchangeable aluminium and impaired cation exchange capacity, leading to nutrient imbalances, aluminium toxicity and declines in crop yield. Spatial patterns of acidification vary with climate, soil texture and land-use history, underlining the importance of site-specific management. Mitigation strategies include liming, incorporation of organic amendments, optimised manure recycling and selection of vegetation that enhances base cation inputs or promotes neutralisation. Understanding the interplay between biochemical reactions, soil buffering phases and agronomic practices is essential to safeguard soil health, maintain productivity and limit downstream impacts on water quality and ecosystem function.

Research from Nature Portfolio

Studies have shown that large-scale afforestation can moderate soil pH by raising acidity in alkaline soils and lowering it in acid soils, with species-specific threshold values guiding tree selection to improve fertility. Analyses of paddy soils over three decades reveal a mean pH decline of 0.6 units driven by excessive nitrogen fertilisation and acid rain, with spatial hotspots emerging in central cultivation areas. Investigations along urban gradients demonstrate that elevated nitrogen deposition under warm, wet conditions intensifies acidification in pine forests, with altered cation dynamics reflecting changing urban-rural emission patterns.

Soil Acidification Processes in Agroecosystems publication trend

The graph below shows the total number of articles in soil acidification processes in agroecosystems across all publications each year (not limited to Nature Index journals).

Technical terms

Soil pH: A measure of hydrogen ion activity in soil, indicating acidity or alkalinity on a scale from 0 (strongly acidic) to 14 (strongly alkaline).

Cation Exchange Capacity (CEC): The total capacity of soil to hold exchangeable positively charged ions, reflecting nutrient retention and buffering potential.

Base Saturation: The proportion of exchange sites occupied by base cations (Ca²⁺, Mg²⁺, K⁺, Na⁺), expressed as a percentage of CEC.

Buffering Capacity: The ability of soil to resist pH change upon addition of acids or bases, governed by mineral and organic constituents.

Exchangeable Aluminium: Aluminium ions on soil exchange sites that become soluble under low pH, toxic to plant roots and microorganisms.

Nitrification: Microbial oxidation of ammonium (NH₄⁺) to nitrate (NO₃⁻), releasing protons (H⁺) and contributing to soil acidification.

References

1. Impact of long-term fertilization in no-till on the stratification of soil acidity and related parameters. Soil and Tillage Research (2023).
2. Optimization of manure recycling and fertilizer use to meet crop nutrient demands and reduce nutrient losses, a case study in Quzhou, China. Agricultural Systems (2025).
3. Afforestation neutralizes soil pH. Nature Communications (2018).
4. Drivers of spatio-temporal changes in paddy soil pH in Jiangxi Province, China from 1980 to 2010. Scientific Reports (2018).
5. Soil Nutrient Retention and pH Buffering Capacity Are Enhanced by Calciprill and Sodium Silicate. Agronomy (2022).
6. Urbanization in China drives soil acidification of Pinus massoniana forests. Scientific Reports (2015).