Soil acidification effects on nutrient dynamics in paddy rice systems including causes impacts and sustainable management strategies

Soil acidification in paddy rice systems, where soil pH drops below the optimal 5.5–6.5 range, threatens global rice production by impairing root function, nutrient uptake, and microbial activity. This review examines the causes, impacts, and management of soil acidification in key rice-producing regions like China, India, Vietnam, Tanzania, and the USA. Natural processes, such as organic matter decomposition and soil weathering, combined with anthropogenic activities, including excessive nitrogen fertilizer application, acid rain, and acidic irrigation water, drive acidification, particularly in anaerobic paddy conditions. Acidic soils limit the availability of essential nutrients (N, P, K, Fe, Mn, Zn), increase toxic metal levels (Al, Fe, Cd), and stunt root growth, resulting in yield losses of 5–25% and reduced grain quality. For example, in China’s Jiangxi Province, pH levels of 4.5–5.0 reduce nitrogen availability by 15–20%, while in Vietnam’s Mekong Delta, acid sulfate soils (pH 3.7–4.5) decrease phosphorus uptake by 25–30%. Acidification also disrupts soil microbial diversity, hindering nutrient cycling processes like nitrification and phosphorus solubilization. Mitigation strategies, such as applying lime, biochar, or organic matter, can raise soil pH, improve nutrient availability, and reduce metal toxicity, boosting yields by 5–20%. However, high costs and limited access, especially for smallholder farmers in Africa and Asia, restrict adoption. Acidification leads to economic losses and threatens food security by disrupting global rice supplies. Future research should focus on cost-effective amendments, developing acid-tolerant rice varieties, and exploring climate-acidification interactions to support sustainable rice production.