Yields and Factors Affecting the Yield Fluctuation of Early Ripening Satsuma Mandarin in Greenhouse Culture

Abstract

In greenhouses heated from early December (plot A) and early Jannuary (plot B), and in an open field (plot C), early ripening satsuma mandarin ‘Miyagawa Wase’ and ‘Okitsu Wase’ trees were densely planted in sub plots in combination with organic substance application (1.5 t/10 a/year of rice straw and twice as much rice straw as normal) and fertilizer application (N: 27, P2O5: 24, K2O: 22 kg/10 a/year and 1.5 times the recommended rate). Yields and factors which affect the yield fluctuation were analyzed by employing data from 3 years old, the following year of planting, to 12 years old. There was no significant difference in the yield, leaf area index (LAI), flower-bud count, and other various parameters between organic substance treatments or between fertilizer treatments. Though plot A showed an appreciable yield fluctuation and reduction in yield due to removing filler trees, this cultivation system showed a greater potential yield compared to plot B. LAI in ‘Okitsu Wase’ was larger than that in ‘Miyagawa Wase’ until the filler trees were removed, so the initial yields of the former tended to be slightly higher. Relationships between some factors vs. yield per unit land area were determined. The results clearly indicated that LAI was the strongest factor affecting yield in different growing conditions (plots A, B, and C) and cultivars (‘Miyagawa Wase’, ‘Okitsu Wase’). The trees growing in the greenhouse heated from early December (plot A) had a small number of flower buds, but they represented high fruit set percentages and showed a comparatively strong correlation between the number of flower buds and yield.