Fibrous Root Distribution of ‘Pineapple’ Orange Trees on Rough Lemon Rootstock at Three Tree Spacings1

Fibrous root densities were determined for 16-year-old ‘Pineapple’ orange [ Citrus sinensis (L.) Osb.] trees on rough lemon (C. jambhiri Lush.) rootstock spaced 3.0 × 4.6 m, 4.6 × 6.1 m, and 6.1 × 7.6 m and growing in a deep, central Florida sandy soil. Samples were taken from 1.9 m deep borings at 2 dripline locations and midway between trees in the row and between adjacent rows. The fibrous root systems penetrated to 1.9 m and were well-distributed. Samples from the widest spaced trees generally had lower root densities while the densities of samples from the other spacings were greater and suggested the overlapping of adjacent root systems. Root density was greatest in the surface sample for all spacings and generally decreased with depth. The extensive development and density of the fibrous root systems suggested that root competition was not likely to be a primary limiting factor in higher density plantings grown under comparable conditions.