THE 10-YEAR PERFORMANCE AND SURVIVAL OF 'MARSH' GRAPEFRUIT TREES ON SUN CHU SHA MANDARIN AND VARIOUS CITRUMELO ROOTSTOCKS ON RIVIERA SAND, DEPRESSIONAL, AN ALFISOL

摘要

'Marsh' grapefruit (Citrus paradisi Macf.) trees were planted in 1991 in double-row beds formed from Riviera sand, depressional, an Alfisol with a loamy horizon at depths between 20 to 40 inches. Each bed was planted with approximately 75 trees on a single rootstock. There were two replicate blocks and in each block there was one bed of trees on each rootstock. There were eight rootstocks: six numbered citrume-los (Citrus paradisi x Poncirus trifoliata [L] Raf.), Swingle cit-rumelo, and Sun Chu Sha mandarin (Citrus reticulata Blanco). Cropping began in the 1993-94 season and was measured for all trees through the 2002-03 season. Mean cumulative yield totaled for the 10 seasons varied little among rootstocks and ranged from 28 to 40 boxes/tree. Fruitsamples collected in the 1999 through 2001 seasons showed no difference in juice quality among rootstocks. Trees on Swingle and several other citrumelos were about 9.5 feet tall at age 10 years and the largest trees were 30% taller. Tree health, tree decline and ultimately tree loss, appeared to be strongly related to relative elevation, depth to the argillic horizon, and water table fluctuations. Visual symptoms of tree decline were observed first in the area of lowest elevation, but were eventually observed throughout the planting. Recorded observations of the perched water table showed that the soil was saturated to the surface for extended periods in the lowest area, and to a lesser extent in other areas. Based on longevity, Sun Chu Sha root-stock was apparently better adapted to the site conditions than the citrumelo rootstocks. However, the trees on Sun Chu Sha were also removed due to their unsatisfactory commercial performance.