Field scale soil characterization using pedostructural properties

Accurate soil characterization is crucial for understanding soil-water interactions and allow for better on-farm agricultural and environmental management. Current soil characterization methods lack quantitative attributes that integrate the soil mapping units with environmental and agronomical models. In this research we propose a methodology to physically characterize the soil water medium using quantitative parameters. We incorporated the continuously measured soil water potential curve and the soil shrinkage curve to extract the physically based pedostructural (PS) parameters needed for characterizing the soil water medium. We discuss a setup that we designed and built to continuously measure the shrinkage and potential curves. The procedure we developed to extract the PS parameters for sandy and silty soils was successfully applied on all soil samples, and the required PS parameters were extracted. We present a methodology to generate and define functional soil mapping units that possess physical and quantitative parameters. We followed a four step general system hierarchical approach overlaying study area map, landform map, and SSURGO map. The fourth step was to validate the generated functional soil units using discriminate analysis performed on the PS parameters extracted for every soil mapping unit. Measuring the shrinkage and potential curves requires a special setup that is not available in traditional soil laboratories. Pedotransfer functions (PTFs) to correlate the PS parameters to soil texture and organic matter are developed and presented. Results of this study show that surface horizon (Ap) have higher PS parameter values than subsurface horizon Bt. The PS concept showed high capabilities in defining the soil mapping units, as concluded from the discriminate analysis that was performed. The functional soil mapping units will help in modeling the soil and thus improve the decision make systems.