Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/1999
Publication Date: N/A
Interpretive Summary: Soil organic carbon is a major contributor to the suitability of soil for agricultural production. Unfortunately, agricultural practices have reduced soil carbon levels leading to poor soil quality, accelerated soil erosion, and increased levels of atmospheric carbon dioxide (a greenhouse gas). Evaluating the significance of soil carbon in global change scenarios and sustainable agriculture requires information on how long-ter agricultural practices affect the cycling of soil carbon including amounts retained in the soil and that released to the atmosphere. We found that soils with high levels of clay that formed under prairie vegetation have a high capacity to store soil carbon as compared to sandy soils that were derived from forests. We concluded that there is substantial potential for some soils to store carbon and help mitigate greenhouse gas production while improving the soils capacity as a nutrient reserve for sustainable agriculture.
Technical Abstract: We used natural C-13 abundance in soils to calculate the fate of C4-C inputs in fields cropped to continuous corn. Soil samples were collected from eight cultivated and six adjacent, noncultivated sites of the Corn Belt region of the central USA. The amount of organic C in cultivated soils declined an average of 68%, compared with adjacent, noncultivated sites. The delta C-13 of cultivated soil profiles that had been under continuous corn for 8 to 35 y increased in all depth increments above that of the noncultivated profiles. The percentage of soil organic C derived from corn residues and roots ranged from 22 to 40% of the total C. The proportion of corn-derived C, as determined by this technique, decreased with soil depth and was minimal in the 50- to 100-cm depth of fine-textured soils. The mean residence time of the non-corn C (C3) ranged from 36 to 108 y at the surface, and up to 769 y in the subsoil. The longer turnover rtimes were associated with soils high in clay. Prairie-derived soils have a greater potential to sequester C than those derived from forests. The significant loss of total C at all sites and the slow turnover times of the incorporated C lead us to conclude that there is a substantial potential for soils to serve as a C sink and as a significant nutrient reserve in sustainable agriculture.