Effect of addition of potassium (K2O) in deep-water hydroponic cultivation of kiwifruit using Actinidia macrosperma rootstock

L.B. Chhetri; T. Okuda; K. Ono; K. Beppu

ISSN: 0972-1045

Effect of addition of potassium (K₂O) in deep-water hydroponic cultivation of kiwifruit using Actinidia macrosperma rootstock

Journal of Applied Horticulture, 2026, 28(1): 267-273.

Effect of addition of potassium (K₂O) in deep-water hydroponic cultivation of kiwifruit using Actinidia macrosperma rootstock

L.B. Chhetri¹*, T. Okuda², K. Ono³ and K. Beppu³

¹The United Graduate School of Agricultural Sciences, Ehime University, Ehime 790-8566, Japan. ²Graduate School of Agriculture, Kagawa University, Kagawa 761-0795, Japan. 3Faculty of Agriculture, Kagawa University, Kagawa 7610795, Japan. Corresponding e-mail: chhetri.lalbah@gmail.com

DOI: https://doi.org/10.37855/jah.2026.v28i01.42

Key words: Fertilization, fruit quality, hydroponic cultivation, ‘Kagawa UP-Ki5’, waterlogging tolerance, K?O, fruit potassium, deep-water culture

Abstract:

Hydroponic cultivation of kiwifruit is a novel production system which aims to enhance yield and fruit quality under challenges induced by global climate change. This experiment studied the effect of additional K₂O fertilization in non-circulating deep-water hydroponic cultivation of A. rufa x A. chinensis var. chinensis ‘Kagawa UP-Ki5’ kiwifruit. Seven years old ‘Kagawa UP-Ki5’ kiwifruit vines grafted on waterlogging tolerant rootstock Actinidia macrosperma were used in the experiment. The hydroponic fertilizers, OAT (OAT House No. 1 and 2) and K₂O (OAT House No. 10) from OAT Agrio Co. Ltd., Japan were used in the experiment. Two fertilization regimes, 1/4-strength OAT and K₂O added 1/4-strength OAT nutrient were applied for five and four vines respectively in 2024. In 2025, four vines were applied with 1/4-strength OAT, and three vines were applied with K₂O added 1/4-strength OAT nutrient. Growing water solution, vegetative and fruit quality parameters were assessed to evaluate the treatment effects. Higher electrical conductivity in K₂O added 1/4-strength OAT condition resulted in less water consumption by vines in both years. Additional K₂O applied in the growing water solution did not improve the fruit weight and total soluble solid content of fruit. The fruit produced from K₂O added 1/4-strength OAT treated vines were significantly higher in potassium content indicating production potential of potassium fortified kiwifruit in deep-water hydroponic cultivation. However, further study is necessary to optimize sugar accumulation in hydroponically grown kiwifruit.