Estimating soil physical properties using more readily available data

摘要: Comprehensive soil physical information has rarely been provided by land resource surveys in Australia. To a large extent, this Handbook aims to rectify the situation by providing relatively inexpensive and robust methods for direct measurement. The problem remains that because of time and cost, some soil physical properties-most notably the soil hydraulic properties K (Q) and V|/(9)(Chapters 3—11)-can only be measured at a limited number of sites during a routine survey. Therefore, to allow spatial prediction, relationships with more readily mapped soil properties must be established. Most such relationships, orpedotransfer functions (Bouma ct al. 1986), will have a degree of empiricism and during a survey it is best to develop locally calibrated predictive systems. This chapter provides a guide to procedures that can be used to estimate soil hydraulic properties when local calibration is possible. The procedures involve the methods of direct measurement outlined in previous chapters. We also present some procedures for estimating soil hydraulic properties when local calibration is not feasible. These latter procedures are only appropriate for broad-scale planning purposes or for directing further studies; for example, they could be used for initial sensitivity analyses with a simulation model to guide programs of field measurement. Procedures for estimating other soil properties such as bulk density, shrinkage and aggregate stability have been proposed in the literature but we do not encourage their use for two reasons. First, direct measurement is not particularly difficult and there is a dearth of such data across most parts of Australia. Second …