Root growth of three onion cultivars

Abstract Three onion ( Allium cepa L.) cultivars, Valenciana de Grano, Staro and Southport White Globe, were grown at a semi-arid site in northeast Spain in PVC tubes and in drip irrigated field plots. Shoot dry matter and root length were measured at different sampling dates. Under field conditions root length was measured at different soil depths. A linear regression model was developed to represent root growth: lnRL = a + b InSDW, (R 2  = 0.95-0.96), where RL is total root length (cm per plant) and SDW is total dry weight (g per plant). Valenciana de Grano shows a significantly different intercept (a) versus the other cultivars (P  −1 . The maximum root length densities (Lv) achieved from 0 to 20 cm depth were 8.1–9.1 cm.cm −3 . These results on Lv values are much larger than those reported in literature, probably as a result of high-frequency fertigation. This pattern of root elongation and the root density and distribution have many practical implications for the design of irrigation and fertilization strategies, also for simulation models.