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ARS Home » Pacific West Area » Kimberly, Idaho » Northwest Irrigation and Soils Research » Research » Publications at this Location » Publication #166972
Title: IRRIGATION INCREASES INORGANIC CARBON IN AGRICULTURAL SOILS

Author
item Entry, James
item Sojka, Robert
item SHEWMAKER, GLENN - UNIVERSITY OF IDAHO

Submitted to: Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2004
Publication Date: 2/17/2004
Citation: Entry, J.A., Sojka, R.E., Shewmaker, G.E. 2004. Irrigation increases inorganic carbon in agricultural soils. Environmental Management. 33(Supplement 1):S309-S317.

Interpretive Summary: Inorganic carbon reactions are among the most important chemical reactions that occur in irrigated soils and may contribute to the total amount of C sequestered in those soils. Since carbon dioxide can escape from soils to the atmosphere or return to precipitate carbonate minerals, soils are open systems with regard to inorganic carbon. We measured inorganic and organic C stored in southern Idaho soils having long term land use histories that supported native sagebrush vegetation, irrigated moldboard plowed crops, irrigated conservation (chisel) tilled crops and irrigated pasture systems. Inorganic carbon and total carbon (inorganic + organic carbon in soil decreased in the order irrigated moldboard plowed crops> irrigated conservation tilled> irrigated pasture> native sagebrush sites. We use our findings to estimate that amount of possible inorganic and total carbon sequestration if irrigated agriculture were expanded by 10%. If irrigated agricultural land were expanded by 10 percent worldwide and native sagebrush land were converted to irrigated moldboard plowed land, a possible 160 million metric tons inorganic carbon (2.78 percent of the total carbon emitted in the next 30 year) could be sequestered in soil. If irrigated agricultural land were expanded by 10 percent worldwide and native sagebrush land were converted to irrigated conservation tillage, a possible 110 million metric tons inorganic carbon (1.87 percent of the total carbon emitted in the next 30 years) could be sequestered in soil. If irrigated agricultural land were expanded worldwide and native sagebrush land were converted to irrigated pasture a possible gain of 26 million metric tons inorganic carbon (0.04 % of the total carbon emitted in the next 30 years) could be sequestered in soils. Inorganic carbon sequestered from land use changes have little potential to make a significant impact on concentration of atmospheric carbon dioxide. However, when coupled with organic carbon and altering land use to produce crops on high output irrigated agriculture, while selected less-productive rainfed agricultural land were returned to temperate forest or native grassland, there could be reductions in atmospheric carbon dioxide.

Technical Abstract: Inorganic carbon reactions are among the most important chemical reactions that occur in irrigated soils and may contribute to the total amount of carbon sequestered in those soils. Since carbon dioxide can escape from soils to the atmosphere or return to precipitate carbonate minerals, soils are open systems with regard to inorganic carbon. We measured inorganic and organic carbon stored in southern Idaho soils having long term land use histories that supported native sagebrush vegetation (NSB), irrigated moldboard plowed crops (IMP), irrigated conservation (chisel) tilled crops (ICT) and irrigated pasture systems (IP). Inorganic carbon and total carbon (inorganic + organic carbon) in soil decreased in the order IMP>ICT>IP>NSB. We use our findings to estimate that amount of possible inorganic and total carbon sequestration if irrigated agriculture were expanded by 10%. If irrigated agricultural land were expanded by 10% worldwide and NSB were converted to IMP, a possible 160 million metric tons of inorganic carbon (2.78 % of the total carbon emitted in the next 30 yr) could be sequestered in soil. If irrigated agricultural land were expanded by 10% worldwide and NSB were converted to ICT, a possible 110 million metric tons of inorganic carbon (1.87 % of the total carbon emitted in the next 30 yr) could be sequestered in soil. If irrigated agricultural land were expanded worldwide and NSB were converted to IP a possible gain of 26 million metric tons of inorganic carbon (0.04 % of the total carbon emitted in the next 30 yr) could be sequestered in soils. Inorganic carbon sequestered from land use changes have little potential to make a significant impact on concentration of atmospheric carbon dioxide. However, when coupled with organic carbon and altering land use to produce crops on high output irrigated agriculture, while selected less-productive rainfed agricultural land were returned to temperate forest or native grassland, there could be reductions in atmospheric carbon dioxide.