Control of citrus sudden death (CSD) has been only achieved by inarching affected trees in the field with tolerant rootstocks such as the 'Swingle' citrumelo. Therefore, the use of nursery trees inarched before planting appears as an interesting strategy for establishing new citrus groves where the CSD has not been yet detected, with the advantage of reducing irrigation needs of trees grafted on 'Swingle'. This research was carried out with the objective to evaluate growth and nutrition status of non-bearing 'Valencia' sweet oranges grafted on multiple and single rootstocks. An experimental grove was planted at 7,0 m x 4,0 m in Cordeirópolis, SP, in October 2005 under a randomized complete block design with 4 replicates. Five treatments were tested in order to compare the performance of trees on single rootstocks of (1) 'Rangpur' lime and (2) ''Swingle' Citrumelo, double rootstock with inarch of 'Rangpur' lime in the trunk of (3) 'Swingle' rootstock or of (4) the canopy and (5) quadruple rootstock (two double rootstocks). Trunk diameters of rootstocks and canopy were evaluated, as well as the number and length of twigs in different canopy quadrants, plant height, canopy diameter and volume at 8 and 14 months after planting in the field. Nutrient concentrations were also evaluated on leaf samples collected in the south and north parts of the canopy after 14 months. Double rootstock trees of Valencia sweet oranges presented more vigorous growth compared to others on single 'Swingle' citrumelo rootstocks, being such difference more evident definite during the high water deficit period of the study. The use of an additional rootstock changed the nutritional status of Valencia sweet orange trees, that presented higher concentration of P, K, Cu and Zn in the leaves than 'Swingle' or 'Rangpur' lime single rootstock plants.
Citrus; citrus sudden death; inarching; plant growth; water deficit; mineral nutrition
