Abstract
Tillage intensity affects soil structure in many ways but the magnitude and type (+/−) of change depends on site-specific (e.g., soil type) and experimental details (crop rotation, study length, sampling depth, etc.). This meta-analysis examines published effects of chisel plowing (CP), no-tillage (NT) and perennial cropping systems (PER) relative to moldboard plowing (MP) on three soil structure indicators: wet aggregate stability (AS), bulk density (BD) and soil penetration resistance (PR). The data represents four depth increments (from 0 to >40-cm) in 295 studies from throughout the continental U.S. Overall, converting from MP to CP did not affect those soil structure indicators but reducing tillage intensity from MP to NT increased AS in the surface (<15-cm) and slightly decreased BD and PR below 25-cm. The largest positive effect of NT on AS was observed within Inceptisols and Entisols after a minimum of three years. Compared to MP, NT had a minimal effect on soil compaction indicators (BD and PR) but as expected, converting from MP to PER systems improved soil structure at all soil depths (0 to >40-cm). Among those three soil structure indicators, AS was the most sensitive to management practices; thus, it should be used as a physical indicator for overall soil health assessment. In addition, based on this national meta-analysis, we conclude that reducing tillage intensity improves soil structure, thus offering producers assurance those practices are feasible for crop production and that they will also help sustain soil resources.
Highlights
A healthy soil must be physically, nutritionally and biologically balanced
The descriptive analysis showed that mean values for soils under perennial cropping systems (PER) were highest for Aggregate stability (AS) and lowest for bulk density (BD)
Switching from moldboard plowing (MP) to NT, had clear benefits documented by increased topsoil AS and decreased soil compaction indicators (BD and penetration resistance (PR)) in deeper soil layers
Summary
Soil physical health is intricately linked to soil structure which influences gaseous exchange, water retention and infiltration, root penetration and nutrient cycling. Soil structure is defined by the arrangement of primary soil particles into secondary units (peds) that are characterized based on size, shape and grade. It reflects the spatial arrangement of solids and voids which are the complementary aspects of the soil structure [4]. Soil aggregate size and stability are used to characterize soil structure because those indicators are correlated with several soil functions, including gas exchange and C sequestration through physical protection of soil organic matter (SOM) [4]. A third key indicator of soil structure is penetration resistance (PR) which is directly correlated with root growth [9]
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