To determine the rates of terrestrial carbon sequestration resulting from both increased cropping frequencies and decreased tillage in north central Montana’s dryland wheat production, soil samples were collected bi-annually with yields and management monitored annually over the course of six years. It was hoped that six years of consecutive management would result in cumulative changes in soil organic carbon (SOC) which could be detected and used to determine annual rates of terrestrial carbon sequestration resulting from the two treatment factors.

Differences between baseline SOC data and SOC data from the sixth year of the story unfortunately were not consistent with well-established carbon sequestration trends for either of the treatment factors being studied. In fact, these comparisons resulted in suggested changes in SOC which were identified as highly improbable. Substantial variation in baseline SOC data was identified as most likely culprit for the questionable sequestration rates.

Because of the concerns with the baseline data, comparisons among treatments at each of the six field sites were made assuming a common unknown baseline. The comparisons resulted in differences (P < 0.05) which were consistent with the established carbon sequestration trends being detected in the 0-10 cm soil profile for two of the six sites tested.

An additional test, the AMBC (active microbial biomass carbon) test, was employed as a means of detecting differences in active microbial biomass carbon pool as a means of indicating changes that are occurring in the total SOC pool. The results of the AMBC test showed no statistical difference between the treatments for the two sites tested but the signal may have been diminished due to a 1 year storage time of the soil samples prior to testing.

Attempts to characterize the response of the AMBC test to sterilized soil produced unexpected results which need to be further investigated so modifications to the AMBC test using sterile soil as a means of standardization across time cannot be recommended at this time.