Soil Structural Stability Influenced by Land Management

Soil structure is an important factor in regulating soil ecological functions and soil chemical, physical, and biological properties. This study evaluated soil structural stability from three locations within the central Great Plains (USA) under different management practices.  The study sites consisted of Alternative Crop Rotation (ACR) and Long-Term Tillage (LTT) near Akron, Colorado, and Knorr-Holden (KH) near Mitchell, Nebraska.  Tillage treatments consisted of no-tillage (NT), reduced tillage (RT), conventional tillage (CT), and moldboard plow (MP). Commercial mineral fertilizer (F) was used as a nitrogen source in ACR and LTT sites while manure (M) plus F treatments were used in KH.  Soil structural stability was evaluated using four indices, aggregate stability index (ASI), mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimension (FD).  At 0-15 cm depth, intensive tillage (CT and MP) in ACR and LTT, reduced (P < 0.05) ASI by 46.7%, MWD by 21.0% and GMD by 8.4% and increased FD by 0.77% compared with NT and RT treatments.  The addition of manure increased (P < 0.05) ASI by 72.2%, MWD by 65.6%, GMD by 32.8%, and reduced FD by 5.5% compared with tillage treatments in ACR and LTT.  Although FD was negatively correlated with MWD and GWD; it provides information not captured by ASI and complements MWD and GWD.  The indices presented in this study, including FD, are effective in measuring soil structural stability and should be considered further in management decisions to sustain soil resources and enhance economic returns.