Research on the actual condition of tree size, yield, quality of fruits and inorganic components in the leaves of a 'Maekawa Jiro' Japanese persimmon (Diosypros kaki Thunb.) orchard in Shizuoka prefecture [Japan]

To clarify the productivity and fruit quality at a production region, the physico-chemical properties of orchard soil and density of planting, size of trees, yield, fruit quality and leaf-nutrients of the Japanese persimmon 'Maekawa Jiro' (Diospros kaki L.) at the main production region were investigated for 4 years (1978-1981). 1) The physico-chemical properties of orchard top soil were good. However most of the orchard subsoil was deficient in phosphoric acid and humus was generally low. Therefore it was necessary to improve the subsoil. 2) The leaf N content in Aug. for 4 years except the tree ringed was in the range of 2.0~2.4%. And investigated trees early in June ringing treatment of 2mm width was seen. The leaf N of tree ringed was from 1.7% to 1.8% and the treatment appeared to weaken the trees. 3) Average tree height was 2.9m and canopy volume was 32 cubic-meter, but great trees of 4.4m and 63 cubic-meter respectively were seen. The utilizing ratio of the orchard was 67% on average, from 50% at close planting to 87% at scattered planting. Therefore the planting must be done systematically. 4) As for productivity, the index of alternate bearing was 40 or more, extremely high. Moreover the range of yield/10a on the average for 3-4 years was from 1. 4t to 2. 5t with an average of approximately 1.95t. Thus the stabilization for productivity is an important concern. The ratio of seeded fruit showed large yearly fluctuation, with 1 to 2 seeds in about 10% of the fruit in a good year to 50% in a bad year. It appeared that the existence of seed in the fruit controlled the physiological fruit drop. 5) The fruit weighted from 210g to 280g and brix in the juice was approximately 14 to 16 degrees. When the yield was high, brix in the juice and fruit weight both tended to be low. Therefore in future it will be necessary to determine a suitable yield taking the quality of fruits into consideration