A catchment scale assessment of soil pH variability: Relationship with geomorphology and climate

The factors influencing soil pH distribution are less certain in drier climates. Climate, soil texture, and soil properties are known to affect soil pH, and quantifying the links between climate, soil properties, and nutrient cycling is important for improved land management. This study investigates the influence of climate and soil properties on soil pH in two medium-scale agricultural catchments (600–700 km²) in eastern Australia. Three sampling campaigns were conducted over a 16-year period (2006–2018), extracting soil cores across the two catchments. Results showed that soil pH decreased with increasing elevation and was significantly correlated with soil organic carbon (SOC). Clay and sand had a minor influence on soil pH. Electrical conductivity (EC) showed inconsistent relationships with soil pH, with low salinity levels limiting its influence. Climate, characterised by increased rainfall and lower temperatures at higher elevations within the catchment, was the primary factor influencing soil pH distribution. Therefore, understanding the relative influence of climatic and edaphic factors on soil pH variability is important for understanding nutrient dynamics and informing land management in agricultural catchments. The findings here are likely to apply to other areas where there is an increasing rainfall gradient. • The factors influencing soil pH distribution are less certain in drier climates. • Orographic rainfall and decreasing temperature with elevation influenced soil pH • Soil pH was significantly correlated with soil organic carbon • Clay and sand had a minor influence on soil pH