Effects of Intentional Alternate Bearing Methods on Tree Growth, Yield and Fruit Quality in Young Tree of 'Aoshima unshiu' Satsuma Mandarin (Citrus unshiu Marc.)

Abstract

To improve the fruit quality and alternate bearing behavior of young 'Aoshima unshiu' trees, they were subjected the following four bearing methods : (1) alternate whole tree bearing (AWB), (2) unilateral bearing within the crown (UBC), (3) alternate branch unit bearing (ABB), (4) whole tree annual bearing (WAB). The cumulative yield per tree during the 12 years in UBC was 8 to 13% higher than those in other bearing methods. The yield in AWB was almost the same as that in WAB plot. In WAB and ABB plots, more than 40% of fruits were classified as size 2L or larger, whereas 26% was ranked in the same category in AWB. In AWB, as much as 70% of the marketable was graded M or L size with high Brix value. Alternate bearing indices of WAB and ABB were, higher than those of AWB and UBC, that of UBC ranked last. Brix values of UBC and AWB were higher than those of WAB, while fruit coloring was significantly advanced in AWB. Volume of the tree crown was the largest in AWB, followed by UBC. The crown volume of the 15-year-old AWB trees was 1.6 times larger than that of the WAB trees. Although UBC and AWB methods produced high marketable fruits of young 'Aoshima unshiu' every year. AWB was judged to be the most suitable based on the ease of labor management.