2017 Volume 16 Issue 1 Pages 41-50
For simultaneous mechanical harvesting of small-flowered spray-type chrysanthemum, the effects of planting systems on flowering period uniformity were studied using the summer-autumn-flowering-type cultivar ‘Okinamaru’. The influence on flowering periods of the planting position in the plant population, which were made up of six rows and seven columns, and the branching node number after pinching were investigated. Flowering periods in the edge rows facing north or south furrows were shorter than in the inner four rows. The difference in the photosynthetic photon flux density of the plant community at the canopy height from about 15 cm below the canopy was smaller for the inner rows than for the edge rows. These results demonstrate that more solar radiation reached the lower leaves of the inner rows. In the three shoots remaining after pinching, shoots from the lower lateral node showed a longer flowering period, but no significant difference was noted between those of upper shoots and middle shoots. In the next three experiments, changing the center inter-row distance, shading around the plant population and pinching were examined to improve the uniformity of flowering. In the first experiment, using the plant population planted north to south in four rows, the center inter-row distance was changed from 15 to 90 cm. Flowering periods of the inner and outer two rows were respectively measured. The difference in flowering periods between those of the inner and outer two rows decreased as the center inter-row distance increased. This was not significant for a more than 75 cm spacing. In the second experiment, shading materials with a 31% shading rate were suspended beside the edge rows under the ten-row condition, and the flowering period of each row was measured. The flowering periods of edge rows were slightly delayed by the shading treatment, but the flowering period uniformity was not improved markedly. In the third experiment, non-pinching, leaving a shoot per plant after pinching, and leaving two shoots per plant were compared under the four-row condition. Flowering period uniformity was improved in the two pinched experiment plots. In conclusion, spacing the center inter-row distance and training one or two shoots per plant improve the flowering period uniformity, which was influenced by the planting position and branching position after pinching.
