The missing carbon link: Are ag lime and groundwater irrigation sequestering carbon?

Bonnie McGill and Steve Hamilton
Kellogg Biological Station, Michigan State University

Presented at the All Scientist Meeting (2015-04-15 to 2015-04-16 )

Farmers routinely add inorganic carbon to row crop soils in the form of crushed lime (e.g. CaCO3 or CaMg(CO3)2) and/or inadvertently as bicarbonate (HCO3-) naturally dissolved in groundwater used for irrigation. In the soil these carbonates can act as either a source of CO2 to the atmosphere or a sink for keeping additional CO2 out of the atmosphere. Yet the relationship between nitrogen fertilizer amount, irrigation, and carbonate fate is not well understood. We are collecting soil porewater from 1.2-3.3 m depths at the KBS LTER Resource Gradient experiment and analyzing their chemistry to trace the fate of inorganic carbon and other ions across a nitrogen fertilizer gradient, with and without groundwater irrigation. This poster will show porewater chemistry results from 2014, the first growing season of porewater sampling.

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