Baseline Soil Quality within a Lower Mississippi River Alluvial Basin Agricultural Watershed.

An assessment was conducted in Beasley Lake Watershed (BLW) near Inverness, MS, in 2008 to obtain a temporal baseline on soil health.  Beasley Lake is an abandoned meander of the adjacent Big Sunflower River, surrounded by an agricultural landscape that is characteristic of the Mississippi River alluvial plain. ARS scientists from the National Sedimentation Laboratory, Oxford, MS, have overseen research in BLW since 1994, as one of three oxbow lake watersheds selected as a component of the Mississippi Delta Management Systems Evaluation Area (MSEA) Project. In 2003, BLW became part of the USDA Conservation Effects Assessment Project (CEAP) Watershed Assessment areas.  An additive Soil Quality Index (SQI) was computed using the Soil Management Assessment Framework (SMAF) for over 200 samples (0-5 cm depth) collected across the BLW.  The SQI was composed from 2 physical, 2 chemical, 4 biological and biochemical, and 2 nutrients indicators.  Sample sites included 3 management scenarios: row crop (RC, 47% of the samples), Conservation Reserve Program (CRP, 31%) (estab. 2003), and quail buffer (QB, 22%) (estab. 2006), distributed in four soil series representative of three aquic taxonomic suborders (Aqualf, Aquept, Aquert). Alligator soil series (Aquert) was not observed within the CRP scenario. SQI and clusters of indicators were compared (p<0.05) considering variations in management practices and soils suborder. Comparisons of index outcomes showed that samples from Aqualfs (Forestdale and Dundee, 67% of the samples), had greater SQIs than from the Aquept (Dowling, 17%), and were significantly different from those in Aquert (Alligator, 16%). Without regard to suborder, SQI was greater for the CRP scenario (did not include Aquerts) than for the QB and RC, with RC being the lowest for all scenarios. Chemical indicators for RC were higher than those for the QB. SMAF showed that soils under CRP scenario were functioning at 89% and 84% of full potential when they belonged to Aqualfs and Aquepts, respectively. Soils under QB functioned at 77%, 74% and 70% of potential, while soils under RC were functioning at 73% and 71% and 70% for Alfisols, Inceptisols and Vertisols, respectively. These results were attributed to higher physical, biological and biochemical, and nutrient indicator scores for CRP than for QB and RC scenarios.