園芸ジャーナル
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概要

Effect of Hydrogels in Three Substrates on Growth and Ornamental Quality of Apple Mint (Mentha suaveolens) in Unirrigated Green Roofs

Hui XU, Kyung-Jin Yeum, Yong-han Yoon, Jin-Hee JU*

Green roofs have positive effects on urban settings, leading to improvements in aesthetics and energy consumption of buildings. However, green roofs are extremely difficult environments for plant growth and survival because water availability fluctuates dramatically and is often limited between dry periods and rain events. We analyzed the effects of different concentrations of a water-retention additive, hydrogel, in green-roof substrate mixtures on the growth and ornamental quality of Mentha suaveolens. Coir and perlite were mixed in the ratio of 80:20 (coconut coir dust to perlite, v/v; referred to as C₄ P₁ ), 50:50 (C₁ P₁ ), or 20:80 (C₁ P₄ ) at a substrate depth of 20 cm. Hydrogel (hydrophilic polymer: medium, w/v; dry weight basis) was added to the substrate mixtures at 0 (control), 0.25, 0.5, 1.0, or 2.0 kgm^-3. All plants were watered every two days in the first week until they were well established, and then were not irrigated. The substrate with high coir substrate content increased the growth of Mentha suaveolens under drought conditions, but decreased the ornamental quality in rainy conditions. This study revealed that substrate C₄ P₁ , which has high concentration of coir, is not recommended for Mentha suaveolens in the rainy season. The addition of hydrogel increased the growth and ornamental quality of Mentha suaveolens in substrates C₁ P₁ and C₁ P₄ under drought condition. Moreover, substrate C₁ P₄ with 1.0 kg m^-3 added hydrogel was optimal for Mentha suaveolens growth on green roofs, regardless of drought and rainy conditions.