Measurement and Monitoring Soil Carbon
Lab work
Two types of data sets will come to the lab from the field: composite soil samples and cumulative mass soil. The composite samples
are used to determine soil carbon concentration (g C kg-1) while the soil composite soil samples are used to calculate the
SOC stocks (kg C m-2). The soil processing procedures are described in the standard operating
procedures (CLICK HERE to view pdf) for soil processing and are only summarized in Table 1.
Table 1. Procedures in soil sample processing and laboratory analyses
| Step | Composite soil samples | Cumulative mass soil samples |
| Air-dry the soils samples | Spread your sample out as a thin layer into a shallow tray. Drying can be done in large room, a custom-made solar dryer, or a forced-air oven at 40 C. Break up clods as far as possible to aid drying. It is important to ensure that no material from a sample is lost or discarded as weights of soil fractions are to be recorded on processing. Contamination from dust, plaster or other potential contaminants should be avoided. |
Spread your sample out as a thin layer into a shallow tray. Drying can be done in large room, a custom-made solar dryer, or a forced-air oven at 40 C. Break up clods as far as possible to aid drying. It is important to ensure that no material from a sample is lost or discarded as weights of soil fractions are to be recorded on processing. |
| Weigh and sieve | Weigh the whole dried soil sample to 0.1 g using a calibrated top-pan balance and record the weight. Sieve the soil with 2 mm mesh size sieve and weigh the course fragments (> 2 mm). | Weigh the whole dried soil sample to 0.1 g using a calibrated top-pan balance and record the weight. Sieve the soil with 2 mm mesh size sieve and weigh the course fragments (> 2 mm). |
| Sub-sample | Sub-sample a fine soil fraction and send to a lab for carbon concentration analysis. Store adequate fine soil sample (~ 750 kg) in case further analyses are required later. |
Determine gravimetric moisture content on a subsample. See an example |
| Measure soil organic carbon concentration | Measure soil organic carbon concentration in a soil lab. When sample is size reasonably large, infrared spectral measurement is a cheaper and rapid alternative method to the conventional method. In this case you will analyze a subset of the soils samples (~10%) using conventional laboratory procedures to calibrate and validate the infrared spectral measurements. |
Calculate soil mass per unit volume of soil. Determine volume of soil using auger diameter and auguring depth. |