Soil Quality Assessment: Past, Present and Future

Soil quality assessment may be one of the most contentious topics ever debated by the soil science community. Our objective is to examine the history, present status, and potential for using soil quality assessment as a tool to monitor soil physical, chemical, and biological effects of management decisions that may affect soil and water resources. Differences between inherent and dynamic soil quality and various approaches for assessment are identified and discussed. Four assessment indices, the Agroecosystem Performance Assessment Tool (AEPAT), Soil Conditioning Index (SCI), Cornell Soil Health Test, and Soil Management Assessment Framework (SMAF) are examined. The SCI predicts changes in soil organic matter (SOM) and is a good first step toward more comprehensive assessment, but it focuses only on a single indicator. The AEPAT, Cornell Soil Health Assessment, and SMAF offer a more comprehensive soil quality assessment by including biological, chemical, and physical indicators. One SMAF study showed that including at least three years of forage resulted in higher index values than growing continuous corn (Zea mays L.) because the latter had lower soil pH, decreased macro-aggregate stability, and lower microbial biomass carbon. Another study within the Iowa River South Fork watershed showed that overall, soils were functioning at 87% of their full potential. The lowest indicator score was associated with SOM (0.60) because the average value was only 28.4 g kg. A third study showed that the SMAF could separate cropping groups not recognized by the SCI. Opportunities for collaboration to further improve the SMAF are discussed with the long-term goal being to provide tools to help guide soil management and use decisions and thus ensure longterm sustainability of our soil, air and water resources.