A Soil Quality Index for Alabama

Abstract

Soil quality is how well soil performs the functions expected of it. Many of Alabama’s agricultural soils are considered poor quality due to compaction, excessive runoff, a history of severe erosion, low soil organic matter, and lack of cover crops. Routine soil testing does a good job of evaluating the status of plant nutrients in the soil but it does not provide farmers with the overall quality or health of their soil. There has been some research on using a soil quality index (SQI) but defining the parameters to use has been difficult. Most studies agree that a SQI must be determined on a regional basis due to differences in soils and their uses. The objective of this study was to determine a SQI for Alabama soils by measuring soil parameters that are inherently associated with soil quality in a soil testing lab and make such service available for farmers and gardeners. Paired samples from fields with similar soils and landscapes, but different yields, were taken from farms in Alabama and Georgia. Long-term fertility experiments were also sampled in Alabama. The samples were then analyzed for soil organic matter (SOM), potentially mineralizable N, pH, P, K, Ca, Mg, micronutrients, electrical conductivity, CEC, aggregate stability, and respiration. Each of the parameters were assigned a predetermined weight. Weights for each parameter were summed up to determine a SQI based on 100 for each soil. The final SQI includes selected chemical, physical and biological indicators that are easily and inexpensively measured in a routine soil testing laboratory. Through a process of correlations and iterations, the final parameter weights for SQI are proposed for Alabama. The SQI was significantly related to yield for the long-term research samples but not the farmer samples.