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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Water Management and Systems Research » Research » Publications at this Location » Publication #403119
Research Project: Improving Resiliency of Semi-Arid Agroecosystems and Watersheds to Change and Disturbance through Data-Driven Research, AI, and Integrated Models

Location: Water Management and Systems Research

Title: Land management affects soil structural stability: Multi-index principal component analyses of treatment interactions

Author
item Mikha, Maysoon
item Green, Timothy
item Untiedt, Tyler
item HERGRET, GARY - University Of Nebraska

Submitted to: Soil and Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2023
Publication Date: 9/20/2023
Citation: Mikha, M.M., Green, T.R., Untiedt, T.J., Hergret, G.W. 2023. Land management affects soil structural stability: Multi-index principal component analyses of treatment interactions. Soil and Tillage Research. 235. Article e105890. https://doi.org/10.1016/j.still.2023.105890.
DOI: https://doi.org/10.1016/j.still.2023.105890

Interpretive Summary: Soil structure is an important factor for soil ecology and soil physical and biological processes. Assessing soil aggregate stability is key for evaluating soil structural quality, water and nutrient transport, as well as soil erosion potential. The objective of this study is to evaluate the effectiveness of multiple soil aggregate indices to quantify soil structural development using long-term data from three locations in Colorado and Nebraska. Long-term experiments at these sites include different tillage and nutrient treatments. High fractions of macroaggregates present in soil are reflected in soil aggregate indices, which in turn reflect the strong soil structural stability. This new application of a fractal dimension (FD) indicated soil aggregates fragmentation, soil structure destabilization, and land degradation. At 0-15 cm depth, intensive tillage treatments significantly reduced the aggregate stability index (ASI), and metrics of average aggregate size, whereas FD increased compared with no-tillage and reduced-tillage treatments. The addition of manure increased ASI and aggregate size indices substantially, and reduced FD compared with non-manure fertilizer treatments. The low biomass production, due to dry conditions, tillage practices, and the fine nature of soil types, all contributed to decreased soil organic carbon, which in turn reduced soil aggregation and enhanced soil fragmentation. The FD index is a viable indicator for soil aggregation because it evaluated the susceptibility of the soil to disintegrate into smaller aggregates or soil particles that may lead to enhanced soil erodibility and nutrient losses. In general, soil structural stability needs to be carefully considered in any management decisions to conserve soil resources and sustain/enhance economical returns.

Technical Abstract: Soil structure mediates soil functioning and can be influenced by agricultural management practices (cropping intensity, tillage, and nitrogen source). This study evaluated the effectiveness of multiple soil aggregate indices to quantify soil structural development using long-term data from three locations within the central Great Plains: Alternative Crop Rotation (ACR) and Long-Term Tillage (LTT) near Akron, Colorado, and Knorr-Holden (KH) near Mitchell, Nebraska. Tillage treatments include 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 aggregate size classes were measured in the laboratory, and aggregate stability index (ASI), mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimension (FD) were calculated to evaluate soil aggregation using linear regression and principal components analysis (PCA). At 0-15 cm, intensive tillage treatments (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. The PCA indicated clear effects of M on aggregate structure and stability, indicating that manure addition could compensate for the tillage operations in sustaining soil structural stability. Explanatory variables FD and ASI were orthogonal across the three sites, while FD was negatively correlated with MWD and GWD; thus, FD provides information not captured by ASI and complements MWD and GWD. The evaluated indices appear to be effective in measuring soil aggregation and structural stability and should be considered further in management decisions to sustain soil resources and enhance economic returns.