Abstract
A non-replicated planting of ‘Valencia’ orange [Citrus sinensis (L.) Osb.] trees on 19 rootstocks was established near Immokalee in 1991 to evaluate tree performance on a scale approximating commercial conditions. Trees on various standard or new rootstocks ranging from citranges [C. sinensis x Poncirus trifoliata (L.) Raf.] and citrumelos (C. paradisi Macf. x P. trifoliata) to Cleopatra, Sun Chu Sha, and Changsha mandarins (C. reticulata Blanco) were grown in a commercial nursery. Individual beds of 98 trees on one rootstock were planted at 14 × 22 ft (4.3 × 6.7 m; 141 trees/acre (348 trees/ha) in a commercial grove. The soil is mainly Malabar fine sand. Soil pH values were above 8 in places near the edges of the site where calcareous soil from nearby ditches was used to form beds; elsewhere in the site, soil pH averaged 7.8. Tree survival was above 90% except for those on rough lemon (C. jambhiri Lush.) and Cleopatra mandarin that lost 20% to 30% of the trees to blight and the complete loss of trees on sour orange (C. aurantium L.) to tristeza virus. Trees on most rootstocks were about 12 to 13 ft (3.8 m) tall at age 9 years; those on Cleopatra mandarin and F80-5 citrumelo were the tallest at 14.5 ft (4.4 m) and those on Swingle citrumelo were 10.7 ft (3.3 m). The highest cumulative yields across six seasons came from trees on Carrizo and Benton citranges (14 to 15 [90 lb = 41 kg] boxes/tree); the lowest yield came from trees on Cleopatra mandarin (9.5 boxes). From juice quality data obtained in five seasons, the highest pound-solids/box values were from trees on Carrizo, Benton, and Rusk citranges. Thus, ‘Valencia’ trees on several new rootstocks, F80-14, Benton, several numbered citrumelos and on Sun Chu Sha, have the potential to exceed the performance of those on standard commercial rootstocks.
