Tillage Effects on Soil Hydraulic Properties in Space and Time: State of the Science

Authors: Strudley, Mark; Green, Timothy; Ascough Ii, James

Submitted to: Soil and Tillage Research
Publication Type: Review Article
Publication Acceptance Date: 1/17/2008
Publication Date: 3/16/2008
Citation: Strudley, M.W., Green, T.R., Ascough Ii, J.C. 2008. Tillage Effects on Soil Hydraulic Properties in Space and Time: State of the Science. International Journal of Soil and Tillage Research. 99:4-48. 2008.

Interpretive Summary: Soil tillage practices can affect soil hydraulic properties and processes in space and time with consequent and coupled effects on chemical movement and plant growth. This literature review addresses the quantitative effects of soil tillage and associated management (e.g., crop residues) on the temporal and spatial variability of soil hydraulic properties. Our review includes incidental management effects, such as soil compaction, and natural sources of variability, such as topography. Despite limited research on space-time predictions, many studies have addressed management effects on soil hydraulic properties and processes relevant to improved understanding of the sources of variability and their interactions in space and time. Whether examined explicitly or implicitly, the literature includes studies of interactions between treatments, such as tillage and residue management. No-tillage (NT) treatments have been compared with various tillage practices under a range of conditions with mixed results. The trend, if any, is for NT to increase macropore connectivity while leaving total porosity and soil bulk density unchanged compared with conventional tillage practices. This corresponds to a general increase in ponded or near-zero tension infiltration rates and saturated hydraulic conductivities. Similarly, controlled equipment traffic may have significant effects on soil compaction and related hydraulic properties on some soils, but on others, landscape and temporal variability overwhelm wheel-track effects. Spatial and temporal variability often overshadow specific management effects, and several authors have recognized this in their analyses and interpretations. Differences in temporal variability depend on spatial locations between rows, within fields at different landscape positions, and between sites with different climates and dominant soil types. Most tillage practices have pronounced effects on soil hydraulic properties immediately following tillage application, but these effects can diminish rapidly. Long-term effects on the order of a decade or more are less pronounced and often impossible to distinguish from natural and unaccounted management-induced variability. Enhanced data collection and measurement campaigns, combined with improved methods of parameter estimation and theoretical incorporation of management practices and effects within an explicit spatio-temporal modeling framework should aid in the understanding of soil hydraulic behavior due to tillage and related agricultural management.

Technical Abstract: Soil tillage practices can affect soil hydraulic properties and processes in space and time with consequent and coupled effects on chemical movement and plant growth. This literature review addresses the quantitative effects of soil tillage and associated management (e.g., crop residues) on the temporal and spatial variability of soil hydraulic properties. Our review includes incidental management effects, such as soil compaction, and natural sources of variability, such as topography. Despite limited research on space-time predictions, many studies have addressed management effects on soil hydraulic properties and processes relevant to improved understanding of the sources of variability and their interactions in space and time. Whether examined explicitly or implicitly, the literature includes studies of interactions between treatments, such as tillage and residue management. No-tillage (NT) treatments have been compared with various tillage practices under a range of conditions with mixed results. The trend, if any, is for NT to increase macropore connectivity while leaving total porosity and soil bulk density unchanged compared with conventional tillage practices. This corresponds to a general increase in ponded or near-zero tension infiltration rates and saturated hydraulic conductivities. Similarly, controlled equipment traffic may have significant effects on soil compaction and related hydraulic properties on some soils, but on others, landscape and temporal variability overwhelm wheel-track effects. Spatial and temporal variability often overshadow specific management effects, and several authors have recognized this in their analyses and interpretations. Differences in temporal variability depend on spatial locations between rows, within fields at different landscape positions, and between sites with different climates and dominant soil types. Most tillage practices have pronounced effects on soil hydraulic properties immediately following tillage application, but these effects can diminish rapidly. Long-term effects on the order of a decade or more are less pronounced and often impossible to distinguish from natural and unaccounted management-induced variability. Enhanced data collection and measurement campaigns, combined with improved methods of parameter estimation and theoretical incorporation of management practices and effects within an explicit spatio-temporal modeling framework should aid in the understanding of soil hydraulic behavior due to tillage and related agricultural management.