Research on the stability productive technologies of the satsuma mandarin grafted on a dwarf root stock, hiryu

There are few examples that a satsuma mandarin (Citrus unshiu Marcow. cv. 'Otsu-No.4') trees grafted on Hiryu (Poncirus trifoliata (L.) Raf. var. monstrosa) rootstock is introduced, and the yield per 1 tree is remarkable, and the factors include that they decrease because the initial growth of the tree is slow, and the canopy downsizes it by dwarfing when I use a Hiryu rootstock. Therefore I planned how early canopy expansion and secured the yield per tree and increased the number of the trees than a trifoliate orange rootstock, and it was thought that it was necessary to increase the yields per unit area. For canopy expansion effects of different first bearing years (3, 4, or 5 years after planting) on the tree growth, yield and fruit quality of satsuma mandarin trees grafted on dwarf rootstock Hiryu were investigated. No relationship was found between the first bearing age and fruit quality. The later the first bearing, the larger the canopy volume became, however, trees that began to bear from 5 years after planting were large and higher alternate bearers. On the other hand, trees that began to bear from at 3 years after planting showed less growth and production. In consequence, trees that began to bear from 4 years after planting (tree height 172 cm, canopy volume 3.2 cubic m) had the best productivity and work efficiency. To make dense planting, in an experiment, conducted the tree growth (tree height, canopy width, canopy volume), yield and fruit quality of Satsuma mandarin trees grafted on dwarf rootstock Hiryu were evaluated at three planting spaces; The planting spaces distance between trees was 2 m and 1 m (8 years after planting, the distance changed from 1 m to 2 m by tree thinning.). Planting spaces distance and thinning did not affect fruit quality and tree growth, except canopy width of short trees. The use of a 2 m-planting spaces distance, however, resulted in the smallest biennial bearing index and a stable yield. These results suggest that a 2 m-planting spaces distance suitable for 'Otsu-No.4' trees grafted on Hiryu rootstock to facilitate stable annual fruit production and appropriate tree height for labor-effective cultivation.