Tae-Choon Kim

Shoot Growth and Fruit Characteristics of ‘Yumi’ Peach in Response to Side Dressing with Fused Phosphate Fertilizer

This study was carried out to investigate shoot growth and fruit characteristics in 4-year-old ‘Yumi’ peach (Prunus persica) trees in response to various amounts of side dressing with fused phosphate fertilizer (phosphoric acid 17%, FPF) under soil cultivation. The amount of side dressing of FPF was set at 40% of a year’s supply, i.e., 132 g/tree FPF (P2O5 22.4 g/tree) and 22.4 g/tree for the control, 2× (44.9 g/tree), 4× (89.8 g/tree), and 6× (134.6 g/tree), which were supplied via three-split application at 15-day intervals. Shoot length at the fruit maturing stage decreased by 12–16% with increasing amounts of side dressing of FPF up to 6×. The mineral concentration in leaves did not change significantly with increasing levels of FPF. Available P2O5 and Mg contents in soil after fruit harvest were 3.0and 1.8-fold higher under increasing FPF levels (up to 6×) compared to the control, respectively. Leaf SPAD values at the fruit maturing stage decreased with increasing FPF levels, whereas fruit length and width increased with increasing FPF levels. Fruit weights and hardness increased with increasing (up to 6×) amounts of FPF. Finally, free sugar concentrations increased with increasing FPF levels. Therefore, the application of large quantities of FPF via side dressing during early fruit growth can improve fruit quality in ‘Yumi’ peach under soil cultivation. Additional key words: available P2O5, free sugar, fruit enlargement, mineral contents, Prunus persica

Effect of Early Defoliation on Fruit Yield, Reserve Accumulations and Flower Bud Formation in ‘Sinano Sweet’ Apple Trees

‘Sinano Sweet’ apple trees were defoliated at intervals of a month from May to October to simulate damage occured by hail and typhoon in Korea, accordingly fruit yield, reserve accumulations and return bloom were investigated. As the more severe defoliation degree was and earlier defoliation time was, fruit weight and fruit yields were more decreased. Fruit weight and yields of 30% defoliated trees, regardless of the defoliation time, showed no significant difference with those of control. Because carbohydrate contents of the 2-year old branches defoliated before August were even lower than those of branches defoliated after September, it was considered that defoliation time is more effective on the carbohydrate content than defoliation degree. Among the trees defoliated before August, 50% defoliated trees at August contained the lowest carbohydrate by 50% of control. Time and degree of defoliation had an effect on the number of flower buds following year. The number of return bloom in trees defoliated from May to July was decreased by delay of defoliation time and was the lowest in trees defoliated at July. On the other hand, it was not have a significant different between control and trees defoliated since August. Relationship between the number of return bloom and carbohydrate reserves showed positive correlation. As a result, it is considered that fruit thinning, when defoliation occurred in the growing season, needs for strengthening the sink function of remained individual fruit effect on fruit enlargement and for increaseing the carbohydrate reserve effect on return bloom. Additional key words : carbohydrate content, return bloom