Harmonizing Ssurgo Attribute Data Based On Spatial Analysis of Climate.

National Cooperative Soil Survey has launched the Soil Data Join Recorrelation (SDJR) initiative to achieve a seamless SSURGO soil map for the entre US at MLRA and MO levels that is free of political boundaries. The initiative requires the harmonization of soils information and databases in two stages: (i) attributes or soil properties and (ii) spatial databases or soil map unit polygons.  The initiative requires the development of methods and tools to facilitate the analysis of soil map units to harmonize SSURGO data across political and major land resource area (MLRA) boundaries. SSURGO is developed based on soil forming factor model, so the analysis of soil map units attribute and spatial data will likewise be based on these factors. The US Soil Survey has developed maps of soil temperature and moisture regimes based on mean annual precipitation and temperature that are used extensively for classifying soils. The objective of this study is to use soil series as case study to (i) quantitatively analyze soli map units within and across MLRAs and (ii) develop threshold values and numeric criteria for aggregating and/or disaggregating  SSURGO based on climate indicators.  Thornthwaite Precipitation-Effectiveness Index (PE) and Potential Evapotranspiration (PET) were calculated using Parameter-Elevation Regressions on Independent Slopes Model (PRISM) data and were used as climate indicators. The Bowie soil series was used as a case study. The Bowie series is mapped extensively in Texas, Arkansas, Louisiana and Alabama.  The PE index indicates that soil climate differs significantly between all states except for Louisiana and Arkansas.  The largest differences were between Texas and Alabama and Louisiana and Texas.  All states had significantly different PET. The magnitude of these differences along with other soil forming factors can be used as criterion for SDJR decisions to aggregate and/or disaggregate SSURGO soil map units.