Effects of neutralization of acidic soil on vegetative growth, flowering, and leaf mineral contents of passion fruit cultivated in Okinawa
In Okinawa, passion fruit is often cultivated at strong acidic soil, Kunigami-maji. No useful information is available for passion fruit on requirement of neutralization of soil pH, although alkaline soil Jagal originated from unconsolidated lime-rich rock is conventionally used to neutralize Kunigami-maji. Two-year-old passion fruit plants grown in 40-L pots were used, and on May 2, 2012, the plants were pulled out from the pots and the soil was washed out carefully not to damage the root. The plants were replanted and grown in the pots filled with 100% Kunigami-maji, mixture of 98% Kunigami-maji and 2% Jagal, 94% Kunigami-maji and 6% Jagal, or 70% Kunigami-maji and 30% Jagal. Each soil pH was 4.7, 5.4, 6.8, and 7.4. Among the soil pH from 4.7 to 6.8, vegetative growth and flower number were similar, while in alkaline soil (pH 7.4) those were the lowest. Leaf SPAD index decreased as pH increased. Leaf N, P, and K contents were affected by soil pH but differences were small. At alkaline soil, leaf Ca and Mg contents were the highest. Leaf Fe content at alkaline soil was the lowest but difference was not significant. Leaf Mn and Zn contents decreased as soil pH increased. Absorption of minor nutrients might be inhibited by alkaline soil. The shortage of minor nutrients might decrease vegetative growth and flower number. In conclusion, passion fruit prefers acidic soil to alkaline soil, and neutralization of acidic soil (pH 4.7) has no positive effect on vegetative growth and flower number.
Kondo, T., Higuchi, H., Kozai, N. and Ogata, T. (2017). Effects of neutralization of acidic soil on vegetative growth, flowering, and leaf mineral contents of passion fruit cultivated in Okinawa. Acta Hortic. 1178, 93-98
Jagal, Kunigami-maji, leaf analysis, Passiflora, soil pH