Using Active Organic Matter Measurements to Predict Agronomic Performance.

Total organic matter is a very important soil property that is commonly measured in standardized soil tests. However total organic matter is not an ideal indicator of nutrient availability – because the majority of this pool is not plant available and typically changes very slowly over time. Active organic matter is only a small fraction (5-20%) of the soil’s total organic matter, but is very important to crop nutrition since nutrients in this fraction are rapidly cycled and taken up by crops. We evaluated the ability of two rapid and affordable active organic matter measures, permanganate oxidizable carbon and mineralized carbon, to predict agronomic performance (corn grain yield, aboveground biomass, tomato fruit yield) over 8 studies across the United States. Results show that both POXC and mineralized carbon were better predictors of agronomic performance than other soil C fractions evaluated here, and demonstrate the utility of considering active organic matter measurements from a soil health framework.