Comparison of the Trench‐Profile and Core Methods for Evaluating Root Distributions in Tillage Studies

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Abstract
The trench‐profile method has not been widely used to evaluate root distributions in tillage studies because it is generally considered to be more of a qualitative than quantitative technique. The objective of this study was to determine if the trench‐profile method could be used to quantify and compare root development between tillage treatments as effectively as the widely used core method. Tobacco (Nicotiana tabacum L.) roots were evaluated for no‐till and strip‐till treatments on a Typic Hapludult, and corn (Zea mays L.) roots were evaluated for nonsubsoiled and subsoiled treatments on a Typic Paleudult. Distribution of roots with depth were generally similar between methods for a given site and treatment. Coefficients of variation at a given depth were similar between root count methods and increased from approximately 20% near the surface to over 120% at a depth of 1.0 m. For comparisons within a given site, significant (0.05 level) differences in root development between treatments were found at one site using the trench‐profile method, but no significant (0.10 level) differences were found at either site using the core method. Root data were significantly correlated (site r's were 0.89** and 0.87**) between root observation methods, but different relationships were found between study sites. Expressing root data on a proportional basis rather than as an absolute measure (root number or length) appeared suitable to equate data from the two methods. The number of man‐hours required to obtain root data by the trench‐profile method was about one‐fifth of that required to use the core method to obtain comparable amounts of data.