Comparison of Reporting Methods for Root Growth Data from Transparent‐Interface Measurements

Abstract

Transparent viewing planes provide a useful and popular means of observing and quantifying root growth. This study was conducted to compare root growth quantification by soil depth and distribution using three tracing methods of reporting root growth: (i) traced root intensity (traced RI), (ii) traced root‐length density (traced RLD), and (iii) traced root‐length area (traced RLA). These three root‐tracing methods were compared with actual RLD and actual RLA determinations made from the bulk soil volume at the termination of the study. Creeping bentgrass (Agrostis stolonifera L.; syn A. palustris Huds.) sod was planted in clear, flexible polyethylene containers slanted at a 20° angle. During a period of ≈2 mo, root growth by depth was monitored by tracing roots onto clear polyester sheets. None of the reporting methods for traced roots generated root growth measurements equivalent to actual rooting. Traced RLD yielded the best estimates of root quantity at each soil depth, yet, generated poor root distribution estimates. Traced RLA yielded the most accurate estimate of root distribution compared with actual root distribution when data were transformed to a percent basis. Flexible, transparent polyethylene containers used for viewing‐plane measurements of root growth quantification and distribution can, when reported by these three methods, differ substantially from actual bulk soil RLD or RLA. Thus, this transparent viewing‐plane procedure exhibits the same problems inherent in root measurements from rhizotrons and minirhizotrons.