Soil acidification: sources, processes, impacts on soil properties, nutrient dynamics, crop health, and yield. a review with evidence from Ethiopia and Sub-Saharan Africa

Abstract

Soil acidity is a major constraint to agricultural yield in Ethiopia and Sub-Saharan Africa, affecting a large proportion of arable land. This review provides a comprehensive synthesis of soil acidification, its sources, and its impacts on agricultural ecosystems, with evidence from Ethiopia and Sub-Saharan Africa. Natural factors such as parent material weathering and high rainfall, together with agricultural practices including the continuous use of ammonium-based fertilizers and nutrient mining, accelerate soil acidification processes. Soil acidity profoundly alters soil chemical, physical, and biological properties by disrupting nutrient dynamics, including nutrient fixation, leaching, and transformation, which reduce the plant-available pools of essential nutrients such as phosphorus, calcium, and magnesium, while increasing the solubility of toxic metals such as aluminum (Al³⁺) and manganese (Mn). Aluminum toxicity impairs root development and nutrient uptake, negatively affecting crop health and leading to substantial reductions in crop yield and quality. Advances in understanding the physiological mechanisms of aluminum toxicity have supported the development of acid-tolerant crop varieties. Effective agronomic management strategies include liming, integrated nutrient management, application of organic amendments such as biochar, and the use of acid-tolerant crops, alongside emerging technological approaches. However, adoption remains constrained by the high cost of lime and limited extension services. Future research should prioritize cost-effective soil amendments and breeding for enhanced acid tolerance, while policy interventions should strengthen extension services and improve farmers’ access to inputs. This review highlights the importance of integrated and sustainable approaches to managing soil acidity to improve crop health, yield, and long-term food security in vulnerable regions.