Measured Versus Estimated Saturated Hydraulic Conductivity for Some Indiana Soils Using Pedotransfer Functions Derived from Micromorphology.

The development of Hydropedology depends among other things on the success of translating the qualitative and semi-qualitative soil information to quantitative values. Some of the current physical soil properties like pore-size distribution, soil structure and texture are categorical data and are difficult to relate to K_sat by meaningful statistical analysis. The objectives of this research were to (i) estimate K_sat based on pore-size distribution derived from thin-sections; texture; and bulk density, and (ii) establish relationships between field-measured K_sat and estimated K_sat values. Thirty thin-sections from 10 pedons representing loess over till and loess over weathered sandstone were scanned. The images were analyzed and voids as well as solids were classified using imagine analysis software. Based on their size and shape, the voids were divided and index ratios describing proportions of various pore sizes and connectivity were developed. K_sat for the soils represented by thin sections were measured in the field using Amoozemeter and also estimated using soil texture and bulk density method. Multiple and single regression analysis were used to relate these indexes with measured and estimated K_sat values. The measured K_sat values varied from 0.3-0.6 cm hr^-1, while the estimated K_sat based on texture and bulk density varied by an order of magnitude between 0.036 and 0.36 cm hr^-1. The percent of larger pores and pore connectivity were better estimators of K_sat compared to the estimated K_sat based on texture and bulk density. The estimated K_sat based on thin sections were better correlated with field measured K_sat than those estimated based on soil texture and bulk density. Estimated K_sat using thin-sections is important in understanding the controls at a micro scale, and its applications can be useful if combined with other soil information at coarser pedon and watershed scales.