Effects of Nitrogen Concentration in Fertilizer Solution on Vegetative Growth, Flowering, and Fruit Quality in Passion Fruit

抄録

Demand for low acid passion fruit has been increasing, and cultivation methods, such as fertilizer management to produce low acid fruit is required. And so, the effects of N concentration in fertilizer solution on fruit quality were determined in this study. Fertilizer solutions, containing 6, 13, 25, 50, and 100 mM N, were applied to two-year-old passion fruit plants in sand culture. Artificial pollination was conducted and the number of fruits per plant was regulated to be six. Length of the fruit-bearing vine and leaf, SPAD value, stomatal conductance, and leaf mineral contents were measured. Just after harvest, fruit weight, and dimensions were measured and the days after pollination to harvest (DAP) was recorded. After a 10-day-storage at 25 °C, titratable acidity (TA), total soluble solid (TSS), and juice content were measured. Vegetative growth and stomatal conductance increased as N concentration increased up to 50 mM. The number of flowers increased as N increased. Leaf N content increased as N concentration increased. Leaf Ca contents at 25 and 50 mM were higher than those in other treatments, while P, K, and Mg contents were not affected. TA decreased as N increased, while TSS was not affected. Fruit weight and dimensions were not affected, while juice content increased as N increased. DAP increased as N increased. Then, fruit quality was the highest at 100 mM, when leaf N content was 6.7 %. At 100 mM N treatment, DAP elongation might decrease acidity.