Changes in Soil Carbon Storage After Cultivation

Previously published data from 577 paired soil samples were used to predict carbon in cultivated soil as a function of initial carbon content. A 30-cm sampling depth provided a less variable estimate (r2 = 0.9) of changes in carbon than a 15-cm sampling depth (r2 = 0.6). Regression analyses of changes in carbon storage in relation to years of cultivation confirmed that the greatest rates of change occurred in the first 20 yr. An initial carbon effect was present in all analyses: soils very low in carbon tended to gain slight amounts of carbon after cultivation, but soils high in carbon lost at least 20% during cultivation. Carbon losses from most agricultural soils are estimated to average less than 20% of initial values or less than 1.5 kg/m2 within the top 30 cm. These estimates should not be applied to depths greater than 30 cm and would be improved with more bulk density information and equivalent sample volumes.

Reference:

Mann, L. K. 1986. Changes in soil carbon storage after cultivation. Soil Science 142(5): 279-288.

Note: Data provided sum to 577 sample pairs, not 625 pairs as noted in the published paper. This is due to the following errors: (1) In Table 1 of the paper, the values for years in cultivation and number of pairs for Doughty et al. (1954) are reversed. There are actually 3 pairs under cultivation for 35 years, not 35 pairs under cultivation for 3 years; and (2) the 16 sample pairs for Greaves & Bracken (1946) were not included in the data file.