Soil pH as a Master Variable: Implications for Soil Fertility and Crop Productivity – A Review

Soil pH is widely recognized as a “master variable” that regulates a broad range of chemical, biological, and physical processes in soils, thereby exerting a strong influence on soil fertility and crop productivity. This review synthesizes current knowledge on the role of soil pH in controlling nutrient availability, microbial activity, root growth, and overall plant performance, with particular emphasis on its implications for sustainable agricultural management. Evidence from field and laboratory studies demonstrates that soil pH governs the solubility and chemical forms of essential macro- and micronutrients, influences the activity and composition of soil microbial communities, and affects soil buffering capacity and biogeochemical cycling. Acidic soils are often constrained by aluminium and manganese toxicity and reduced availability of base cations, whereas alkaline soils commonly suffer from micronutrient deficiencies and phosphorus fixation. In contrast, neutral to slightly acidic soils generally provide optimal conditions for nutrient uptake, microbial functioning, and root development, resulting in improved crop growth and yield. The review further discusses factors controlling soil pH, including parent material, climate, biological processes, and management practices, and evaluates key strategies for pH management such as liming, organic amendments, acidifying inputs, and precision soil testing. Finally, emerging research directions, including site-specific pH management and integration with climate-smart agriculture, are highlighted. Overall, maintaining soil pH within an optimal range is fundamental for enhancing nutrient use efficiency, sustaining soil health, and achieving long-term agricultural productivity.