Pedotransfer Functions for Cation Exchange Capacity, Available Water Holding Capacity and Soil Organic Carbon for Representative Soils of Southern Highland Zone of Tanzania

Pedotransfer functions are useful tools in estimating the not easily measured and expensive soil properties. They are especially valuable in settings such as the SHZT where limited direct soil measurements are available. The objective of this study was to develop a series of pedotransfer functions and then evaluate which ones best estimate cation exchange capacity (CEC), available water holding capacity (AWHC) and soil organic carbon (SOC). Data from 20 horizons of four representative pedons was used to evaluate the most predictive properties. Best fit multiple linear regressions were used to obtain relationships and identify property coefficients. Examples of pedotransfer functions developed for the SHZT are %SOC = 0.1*hue-0.03*value-0.034chroma (n = 20, r2 = 0.74), CEC (meq/100g) = 0.44*%clay + 9.6%SOC (n=20, r2 = 0.93), and, AWHC (mm/m) = 14.7%SOC + 0.82%clay + 0.35%silt + 0.51%sand (n=12; r2 = 0.96). All color attributes are for moist samples. The results of predicted CEC, AWHC, and SOC were compared to those measured in the laboratory using the t-test, and the two methods did not differ significantly; two-sided p-value=0.93. These results indicate the promising potential of using the easily measured soil properties and cheap in fiscal terms to estimate the not easily measured soil properties.