The impact of tillage on soil organic matter

Abstract

This study investigates the impact of long-term tillage on soil organic matter (SOM) content across two soil depths. Soil samples were collected from a number of sites with conventional tillage and from adjacent agricultural land that has remained untilled for over 20 years. Samples were taken at two depths (0–15 cm and 15–30 cm), and SOM was determined using the loss-on-ignition method. Statistical analysis using post-hoc pairwise comparisons (Holm-Sidak method) revealed a highly significant difference (p < 0.001) in SOM between tilled and untilled soils. However, no significant difference was observed between topsoil and subsoil SOM levels (p = 0.178). Within both depth layers, SOM was significantly higher in the untilled soil compared to the tilled soil (p = 0.002 and p < 0.001, respectively). Differences in SOM between depths within the same tillage treatment were not statistically significant (p > 0.2). These findings indicate that tillage is the primary factor influencing SOM content, causing a substantial decline in SOM regardless of soil depth, while depth alone had no significant effect and no interaction between tillage and depth was observed.