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Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/22/2003 Publication Date: 9/22/2003 Citation: Torbert H. A., S.A. Prior, G.B. Runion. 2004. Impact of the return to cultivation on C sequestration. Journal of Soil and Water Conservation. 59(1):1-8. Interpretive Summary: Growing concern regarding the impact of CO2 on the atmosphere has led to scientist explore the possibility of capturing C in soil as a result of changes in land management. Generally, this requires that land be taken out of cultivated agriculture. However, one potential problem with collecting C in soil is that it may can be quickly eliminated with the return to cultivation. The objective of this study was to examine the impact of converting land back into cultivated agricultural management on soil C within two different soil types. Soil samples were collected from a loamy sand soil and a clay loam soil in central Alabama which had been under different land management systems, including forested, permanent pasture for greater than 40 years, and permanent pastures which had been converted to continuous cultivation for 1 and 2 years. Within the loamy sand soil, land management locations also included continuously cultivated, fallowed for 5 years, and returned to cultivation after being fallowed for 4 years. Soil samples were analyzed for total N, total C, soil C:N ratio, and bulk density. The clay soil had higher capacity to capture C, compared to the loamy sand soil. In the clay loam soil, little differences could be observed between the forested soil and the permanent pasture, while in the loamy sand soil, large differences were observed for C between the forested and the permanent pasture sites. The results indicate that the vulnerability of soil to lose sequestered C may depend on the soil type. Clay soils, although having higher levels of C, may lose as much as 55% of its C with as little as 2 yrs of cultivation, while sandy soils may show no significant effect on C content within the same time frame. Technical Abstract: A growing body of science indicates that C can be sequestered in soil as a result of changes in land management. Generally, this requires that land be taken out of cultivated agriculture; however, it has been postulated that gains in soil C can be quickly eliminated with return to cultivation. This study examined the impact of converting land back into cultivated agricultural management on C sequestration within two different soil types. Soil samples from nine depth increments (0-5, 5-10, 10-15, 15-30, 30-45, 45-60, 60-75, 75-90, 90-105 cm) were collected from a Blanton loamy sand (loamy, siliceous, subactive, thermic Grossarenic Paleudults) and a Urbo clay loam (fine, mixed, active, acid, thermic Vertic Epiaquepts) in central Alabama, USA, that were under different land management systems. Management systems included forest , permanent pasture, and pasture converted to continuous cultivation for 1 and 2 years. Within the loamy sand soil, land management also included continuously cultivated, fallowed, and returned to cultivation after fallowed. Soil samples were analyzed for total N, organicl C, soil C:N ratio, and bulk density. The clay soil had higher capacity to sequester C, compared to the loamy sand soil but, little differences could be observed between the forested soil and the permanent pasture. In the loamy sand soil, large differences were observed for C between the forested and the permanent pasture sites. The results indicate that the vulnerability of soil to lose sequestered C may depend on the soil type. Clay soils, although having higher levels of C, lost much (55%) of its C with 2 yrs of cultivation, while sandy soils showed no significant loss of C content within the same time frame. |
