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.