Evaluation and Development of Pedotransfer Functions for Estimating Soil Water Holding Capacity in the Tropics: The Case Of Sokoine University of Agriculture Farm in Morogoro, Tanzania

Direct field measurements of soil hydraulic parameters including the soil moisture retention are fraught withtechnical difficulties, making use of Pedo transfer functions key for their estimation. The PTFs of Tomasella andHodnett were evaluated for their applicability to estimate soil water retention capacity at matric potentials of 1,10, 33, 100, 1500 kPa using soil texture and organic carbon measured from the Sokoine University ofAgriculture (SUA) farm. The Tomasella and Hodnett PTFs underestimated moisture retention at 1 and 1500kPamatric potentials while it overestimated the moisture retention at 10, 33 and 100kPa. New multiple linearregressions for the estimation of soil moisture retention were derived using percentage silt and clay, organiccarbon and bulk density and moisture retention at 1, 10, 33, 100 and 1500kPa measured from the SUA farm. Inthe newly developed PTFs, percentage clay and organic carbon explained well soil moisture retention at 0.1 kPaand AWC while moisture retention at other matric potentials could be well explained by percentage clay, organiccarbon and bulk density. The evaluated PTFs of Tomasella and Hodnett produced reliable estimates of soilmoisture retention at 33kPa and 1500kPa. However, the PTFs derived from locally measured soils improved theefficiency of soil moisture retention prediction with all used physicochemical properties significantlycontributing to soil moisture retention at different matric potentials.