Management Practice Effects on Surface Total Carbon: Differences in Spatial Variability Patterns

Lack of information about the spatial variability of soil C in different management systems limits accurate extrapolation of C sequestration findings to large scales. The objectives of this study were to: (i) describe and quantify variability of total C in three management systems, chisel‐plow (CT) and no‐till (NT) with conventional chemical inputs and a chisel‐plow organic management practice with cover crops (CT‐cover) 15 yr after conversion from conventional management; (ii) assess the strengths of spatial correlation in the three studied systems; and (iii) evaluate contributions of topography and texture to the overall total C variability and its spatial components. The data were collected at 12 60 by 60 m plots at the Long Term Ecological Research site, Kellogg Biological Station, MI. The data consisted of elevation measurements taken on a 2 by 5 m grid and a total of 1160 measurements of total C, sand, silt, and clay contents taken from the 0‐ to 5‐cm depth. Overall variability of total C in NT was more than four times greater than in CT, and in CT‐cover the variability was more than two times greater than CT. Spatial correlation of total C was the strongest in NT, followed by CT‐cover, and then by CT. Stronger spatial structures in NT and CT‐cover were found to form in response to topographical and texture gradients. Effects of texture were largely associated with topographical effects; however, even when topography was controlled for, texture still substantially contributed to explaining total C variability.