title: Carbon export from the raccoon river, iowa: patterns, processes, and opportunities.
abstract: Farmed landscapes are engineered for productivity, and research suggests they contribute a disproportionate share of inorganic C to the Mississippi River and Gulf of Mexico. Here we use alkalinity and total organic C (TOC) measurements collected from the Raccoon River of Iowa to (i) evaluate inorganic and organic C concentrations and export patterns, (ii) compare current trends to historical conditions, and (iii) link C transport processes to current land use management. Export of inorganic C averaged 106,000 Mg per year and contributes 90% of the C flux from the basin. Alkalinity concentrations are unchanged from 1931 to 1944 levels (∼53 mg L C), but inorganic C loads have doubled due to increasing discharge. Carbonate-rich glacial deposits and agricultural lime provide a large source of inorganic C, and results confirm that alkalinity export in the Raccoon Basin is transport limited. Although fertilization and tillage practices have possibly helped increase C fluxes over the last 70+ yr, the overriding factor on inorganic C export is discharge. Discharge control over C export provides an opportunity for agriculture in terms of quantifying C sequestration for potential C trading. Controlling water flux through soils can limit inorganic C export similar to practices such as reduced tillage and managed rotations.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Jones
authors.forename: Keith E
authors.initials: KE
authors.lastname: Schilling
mesh_terms: D000383:Agriculture; D002244:Carbon; D004784:Environmental Monitoring; D007484:Iowa; D045483:Rivers; D012987:Soil
chemical_list: D012987:Soil; D002244:Carbon