ROOTEDGE: Software for Measuring Root Length from Desktop Scanner Images

One approach for measuring the length of roots washed from soil samples is to use a desktop scanner to acquire binary images and then use image analysis procedures to determine root length. Normally, this approach requires user-adjusted exposure thresholding. The objectives of this study were to develop a procedure for obtaining binary images of root samples with a desktop scanner that does not require user-adjusted exposure thresholding of each image and to test the performance of the newly developed ROOTEDGE program by using images containing single or multiple root segments of corn (Zea mays L.). ROOTEDGE was developed for measuring the length of digitized roots using the edge chord algorithm. It is insensitive to object orientation, has four image-processing operations, and holds only seven lines of the image in memory. Visual comparisons of digitized images with actual root segments showed that root segments with diameters less than 0.15 mm were not being completely digitized by the image acquisition procedure and were fragmented in the images. The most complete root images were produced by using the highest available scanner resolution and the lowest scanner threshold level for exposure. Using the closing image-processing operation in ROOTEDGE with a test coefficient of 1 also helped to join fragmented objects within images and improved the correlation of ROOTEDGE measurements to direct measurements. Ratios of ROOTEDGE length measurements to manual line-intersection length measurements ranged from 0.98 to 0.88 for four corn root samples of different sizes. In general, the ROOTEDGE software and image acquisition system accurately measured corn root length without user-adjusted exposure thresholding. Journal Paper no. J-17106 of the Iowa Agric. and Home Econ. Exp. Stn., Ames, IA. Project no. 3282.