Soil Active Carbon and Aggregation Measurements to Help Farmers Assess Progress in Soil Health.

In the agricultural community, maintaining or increasing soil health is important. Some common practices to improve soil health include no till, cover crops, and other methods to increase soil organic matter. There are many possible indicators of soil health, but in this study soil aggregate stability and soil active carbon were measured. Soil aggregate stability is related to water infiltration and the potential for soil erosion, while active carbon can serve as an indicator of a readily-available food source for microbial activity.

The sites involved in this study are all located in Indiana and include: three Purdue Agricultural Centers, 12 farmer sites with conservation cropping systems, six conventional comparison sites, and two soil and water conservation district sites. The conventional comparison sites use tillage and do not use cover crops, and the remaining sites use cover crops and no-till.

In summer 2016, soil samples were collected at the 0-5 cm depth, air dried, and separated into two soil size fractions: 0-2 and 2-8 mm. The wet sieve method was used to measure the mean weight diameter of the stable soil aggregates from the 2-8mm soil size fraction. Samples were sent to the Soil Health Assessment Center in Missouri to be analyzed for soil active carbon content in the 0-2mm and 2-8mm soil size fractions.

The hypotheses were 1) soil aggregate stability and the active carbon content will be greater in the cover crop and no-till treatments than in the no cover crop and tilled treatments; and 2) there will be a greater soil active carbon content in the 2-8mm soil fraction than the 0-2mm soil fraction.