Assessment and development of pedotransfer functions for semi-arid sub-Saharan Africa

The application of process-based hydrological models requires the estimatio n of a number of soil hydraulic properties that are difficult, time-consumi ng and costly to measure. This would have severely limited the use of these models had it not been for the development of pedotransfer functions (PTFs ). PTFs are regression equations that relate readily available, easily meas ured soil physical and chemical data either directly or indirectly to soil hydraulic properties. The great majority of work in the development of PTFs has been in the USA and Europe and therefore the soils used have been Amer ican or European. The problem comes in trying to apply PTFs in other areas such as sub-Saharan Africa. This paper describes on-going work at a number of locations in Tanzania that is attempting to evaluate the ability of PTFs to accurately predict soil hydraulic properties. Results are presented whi ch compare PTF-predicted soil hydraulic properties with those measured by t he instantaneous profile drainage method. Results indicate that PTFs develo ped in the USA and Europe do not reliably predict the hydraulic properties of the tested Tanzanian soils. The factors responsible for this and the tec hniques currently being considered for adapting PTFs for use in Tanzania ar e discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.