Management Practice Effects on Surface Soil Total Carbon Differences along a Textural Gradient

Management practice and soil texture are known to affect soil C. Relatively little information exists, however, on interactions between textural and management effects. The objective of this study was to evaluate management effects on soil total C along a textural gradient in well-drained Typic Hapludalfs in southwest Michigan. Three management practices considered in this study were conventional tillage (CT) and no-till (NT) both with conventional chemical inputs, and conventional tillage with leguminous cover crops and no chemical inputs (CT-cover). Four replicate plots were sampled for each practice, with approximately 100 soil samples taken at the 0- to 5-cm depth in each plot. In all management practices, the relationships of total C and N with clay + silt varied depending on the range of clay + silt values, with regression slopes at clay + silt <570 g kg^-1 being 1.5 to 6 times lower than those at clay + silt >570 g kg^-1. Total C in the CT-cover and NT treatments was higher than that in the CT treatment across the whole range of studied textures; however, a greater difference in total C between NT and CT occurred at greater clay + silt contents. Total C in the CT-cover and NT treatments were not different when clay + silt was <600 g kg^-1, while the NT treatment had higher total C than the CT-cover treatment when clay + silt was >600 g kg^-1. The results indicate that the potential for C accumulation in surface soils via NT treatment depends on soil texture.