The mechanical harvesting of processing spinach (spinach used in production of processed food) is potentially becoming a common practice in Japan. Root distribution affects water and nutrient absorption, but how the roots spread in the soil profile during the regrowth period of spinach remains unknown. In this study, we investigate the root systems of processing spinach in topsoil (5 and 15 cm deep) and deeper soil layers (25, 35, 45, and 55 cm deep) cultivated using ratoon harvesting system. The total root length densities (calculated using the average of the densities at 0 and 15 cm horizontal distance from the row for each depth) in the second harvest were more than two-fold greater than those in the first harvest. The root length percentage in the topsoil and root depth indexes indicate that root systems are in shallower soil layers at the second harvest than at first harvest.
