Management effects on soil physical properties in long-term tillage studies in Kansas

Five long-term tillage studies in Kansas were evaluated for changes in soil properties including soil organic carbon (SOC), water holding capacity (WHC), bulk density, and aggregate stability. The average length of time these studies have been conducted was 23 yr. Soil properties were characterized in three depth increments to 30 cm, yet changes due to tillage, N fertility, or crop rotation were found primarily in the upper 0- to 5-cm depth. Decreased tillage intensity, increased N fertilization, and crop rotations that included cereal crops had greater SOC in the 0- to 5-cm soil depth. Only one of five sites had greater WHC, which occurred in the 0- to 5-cm depth. Aggregate stability was highly correlated with SOC at all sites. No-tillage (NT) had greater bulk density, but values remained below that considered root limiting. Soil organic C levels can be modified by management that can improve aggregate stability, but greater SOC did not result in greater WHC for the majority of soils evaluated in this study.