Soil Carbon Storage and Persistence Across a Chronosequence Of Management Intensive Grazing Dairies, An Emerging Land Use Practice In East Central Georgia.

A comprehensive understanding of carbon dynamics and climate change is critical as population grows and fertile land becomes increasingly scarce. Management intensive Grazing Dairies (MiGD) are expanding on row crop fields across the southeastern US, and generally result in a substantial and rapid increase in soil carbon. Thus far, the soil C accumulation rate has been 7.4 Mg C ha^-1 yr^-1 and persists for at least the first 6 years of conversion. Here we assess the persistence of this accumulated soil carbon by measuring CO₂ loss from a set of controlled soil column irrigation experiments. Column experiments were designed by placing replicated (n=3) intact A soil horizons across an MiGD chronosequence, and into 10 cm I.D. ABS cores fitted with a draining end-cap containing a glass fiber filter (Whatman GF/D) and 5 cm length of acid-washed pre-combusted glass wool to aid in drainage. Cores were irrigated weekly with simulated rainwater based on hourly precipitation totals from a nearby weather station. Results from this experiment will help address the extent to which these MiGDs retain soil carbon over longer timescales, an important dimension of the future growth of MiGDs and consequently improve understanding of carbon dynamics in the SE region. The scalability of this project should make it beneficial for future study of land use changes on the carbon cycle across the SE.