Abstract
The root distribution pattern of 17-year-old pineapple orange trees budded on Rough lemon, Cleopatra and Troyer citrange rootstocks were studied by root excavation method at four radial distances, 0-75, 75-150, 150-225 and 225-300 cm from tree trunk, and at three depths, 0-15, 15-30 and 30-60 cm. Fibrous root length density (FRLD) and fibrous root length percentage differed significantly at various depths and radial distances among rootstocks. FRLD was closer to tree trunk on both horizontal and vertical planes. Root density decreased from 0.183 to 0.084, 1.051 to 0.238 and 0.238 to 0.095 cm.cm-3 from 0-15 cm to 30-60 cm depth within 0-75 cm radial distances from tree trunk in trees on Rough lemon, Cleopatra and Troyer citrange, respectively. Cleopatra contains the highest 0.231 cm.cm-3 FRLD as compared to 0.051 cm.cm-3 in Rough lemon and Troyer citrange. Troyer citrange has intensive lateral root development with 84% fibrous roots (FR) within 75 cm radial distance, whereas Rough lemon and Troyer has an appreciable amount up to 225 cm distance (extensive lateral). Cleopatra contained 57% FR in upper soil layer (0-15 cm) (intensive vertical). In Rough lemon and Troyer 54% FR are confined to lower depth 15-60 cm (extensive vertical root development). Troyer and Rough lemon had the same vertical, whereas Rough lemon and Cleopatra showed the same horizontal rooting pattern under arid irrigated ecosystem. Thus, irrigation depth and fertilizer placement should be critically rootstock specific.
