Tillage‐Induced Horizontal Periodicity of Preferential Flow in the Root Zone

Abstract

AbstractFlow patterns for water and solutes in the root zone are often heterogeneous. Understanding the spatial variability of flow is essential in solute‐transport studies and for management of chemical movement. We hypothesized the occurrence of effects of past tillage operations (plowing and seed bed preparation with and without rotovation) on flow patterns and that such effects could be determined from dye tracing. High‐resolution, digitized images of flow patterns on 221 vertical soil profiles (1 m2) perpendicular to the direction of plowing in two sandy loam soils (Typic Agrudalfs) were analyzed using time series analysis. Significant (P < 0.01) horizontal periodicity with a characteristic length equal to the furrow width for the plow (35 cm) was found for the degree of dye coverage in the 0‐ to 25‐cm topsoil layer (12 out of 15 plots) and for the number of stained channels in the 25‐ to 100‐cm subsoil layer (11 out of 15 plots) after plowing and conventional seed bed preparation (harrowing). The 35‐cm‐scale periodic variability of flow patterns in the subsoil was linearly related to the variability of patterns in the topsoil in three out of 17 plots (P < 0.01). Significant (P < 0.05) linear trends with horizontal distance were found for the degree of dye coverage in the topsoil (11 out of 20 plots), and for the number of stained channels in the subsoil (10 out of 17 plots). Rotovating after seedbed harrowing (five plots) reduced the number of stained flow pathways in the subsoil.