C/N Testing in the Lab

The Soil-baking Oven

Because soil is a complex habitat, it hosts a complex variety of soil organisms whose needs are equally diverse.  Depending on one's soil goals (agriculture, industrial, construction, etc.) the types of soil organisms may play an important role.  In agriculture especially, soil organisms contribute to soil fecundity and structure.  Structure in turn has an important role to play in water infiltration, soil aggregation, and pore size.  Because of the complexity of these characteristics, maintaining a habitat that is most conducive to a particular soil organism is vital.  The carbon to nitrogen ratio, then, is an important piece of information for a soil manager.  Most soil biota enjoy a low C:N ratio, since nitrogen is difficult to acquire. 

Soil Being Placed in "boat"

To test the carbon to nitrogen ratio in the SAGE garden samples, soil was placed in a ceramic container known as a “boat.”  Each sample was weighed, and the tare weight of the “boat” subtracted to ensure accuracy.  Then each sample was heated in an oven to 2300 degrees to release the carbon and nitrogen from the sample.  These were read by a computer and a print-out generated with results for each sample.  The SAGE garden has a fairly low C:N ratio of ~10:1, on average.

C/N Ratio Data, plus Sulfur. The "Oatmeal" data is for reference