The soil health tool—Theory and initial broad-scale application

Soil health has traditionally been judged in terms of production; however, it recently has gained a wider focus with a global audience, as soil condition is becoming an environmental quality, human health, and political issue. A crucial initial step in evaluating soil health is properly assessing the condition of the soil. Currently most laboratory soil analyses treat soils as non-living, non-integrated systems. Plant available nutrients have traditionally been estimated with methods that utilize harsh chemical extractants in testing soil for inorganic N, P, K, and micronutrients. Complementary methods, including soil texture, pH, and total soil organic matter, also do not evaluate biological soil aspects. In this paper we introduce and describe the theory behind the Soil Health Tool, focusing on two objectives: 1) to estimate plant available N, P, and K; and 2) to provide an indication of soil health with respect to nutrient and C cycling. The Soil Health Tool is an integrative soil testing approach that measures inorganic N, P, and K with a soil extractant comprised of organic acids. It also estimates potentially mineralizable N and P as influenced by water extractable organic C and N and microbial soil respiration. The Soil Health Tool was designed for use in commercial soil testing laboratories and uses rapid, cost-effective procedures. The tool also offers insight into the complex interactions between soil chemistry and biology and providing additional value to producers through improved plant available nutrient estimates as well as an indication of the soil health status as related to C, N, and P cycling.