Soil survey techniques determine nutrient status in soil profile and metal retention by calcium carbonate

Soil survey techniques can integrate observation, mapping, and interpretation of information on soil nutrients and metals, and thus play an important role in basic and applied soil research. A field survey was conducted on four soil series (MALIK, BHALWAL, SINDHWAN, and SHAHDARA; USDA classification system) in Tehsil Lahore city, Punjab, Pakistan. Soil physicochemical properties and concentrations of nutrients and total metals were analyzed by soil series and depth of soils. Results showed apparent variations of soil indices with soil series and soil depths. Nutrient concentrations in the BHALWAL and SINDHWAN soils were higher than in other soil series, due to the silt loam texture of the two soils that can efficiently retain nutrients. Regarding soil depth, soil physico-chemical properties and concentrations of nutrients and total heavy metals were higher in the most upper soil horizon than the lower horizons, except cadmium (Cd) in the MALIK and BHALWAL soil series and lead (Pb) in BHALWAL and SHAHDARA. As soil depth increased, concentrations of both organic matter and nutrients decreased. The metals were significantly bound to clay and silt particles in the upper soil horizons, which eventually reduced leachability of the metals. Hence, the soil series with more clay and silt contents had capability to minimize metal leaching to ground water. Moreover, concentrations of metals were negatively associated with concentrations of calcium carbonate (CaCO3) that can bind metals. Results suggest that waste industrial products containing Ca can be applied to remediate metal pollution of soils.