Evaluation of Hydrophilic Polymer on the Growth of Plants in the Extensive Green Roofs

This study aimed to determine effects of the use of water-retention additive, hydrophilic polymer, for extensive green roofs on growth of Juniperus chinensis var. sargentii and Euonymus fortunei 'Emerald and Gold' for woody plants, and Carex kobomugi and Carex pumila for herbaceous plants. Five different contents of hydrophilic polymer including 0% (Control), 1.0%, 2.5%, 5.0%, and 10% (polymer: medium (w/w), dry weight basis) were added to each of the container filed with a 100 kg of growth medium. Ten of plants were transplanted in each of square container ($1m(L){\times}1m(W){\times}0.3m$ (H)) built on the roof platforms in randomized complete block design in the $20^{th}$ of May, 2013. In results, excessively high volumetric soil water content, about 97-98%, was found in the substrate under elevated hydrophilic polymer concentration of at least 2.5%, during the entire growing period. The moisture content of the substrate containing 1.0% of hydrophilic polymer was higher about 20% in the range between 70% and 80%, compared tho that of Control substrate in the range between 50% and 60%, for 27 days after transplanting prior to abundant rainfall, indicating that the application of hydrophilic polymer to the extensive green roof substrate is effective to eliminate drought condition by retaining water in the substrate. Euonymus fortunei 'Emerald and Gold' and Carex kobomugi resulting in higher plant growth with 2.5% than those of the other treatment plants. Juniperus chinensis var. sargentii was observed the highest growth under 1.0% hydrophilic polymer treatement, and Carex pumila was founded the best growth with Control respectively. Plants that grown in both the 1.0% and 2.5% hydrophilic polymer survived all, while the plants that grown in the 5.0% and 10% hydrophilic polymer died after 3 months. These results suggest that advantage of the addition of hydrophilic polymer may be greater in drought-tolerant plants, but the mixture proportion of hydrophilic polymer should be determined according to the different features of the plant species being grown.

저관리형 옥상녹화 식물생육을 위한 Hydrophilic polymer의 효용성

본 연구는 저관리형 옥상녹화에서 보수성을 높일 수 있는 식재지반을 조성하기 위해 친수성 중합체인 hydrophilic polymer의 효용성을 평가하고자 현장실험을 수행하였다. Hydrophilic polymer의 농도는 각각 인공배합토 100kg을 기준으로 0%(대조구), 1.0%, 2.5%, 5.0%, 10% 등 총 5가지로 구성하였다. 가로 1.0m, 세로 1.0m, 높이 0.3m로 자체 제작한 실험구에 2013년 5월 20일에 각각 10반복의 식물을 정식하였으며 식재기반 내 토양용적수분함량을 모니터링하였다. 또한 현재 이용되는 수종인 눈향나무, 황금줄사철나무 등의 목본류와 잠재종으로 가능성이 높은 통보리사초, 좀보리사초 등의 사초류를 중심으로 식물생육을 측정하였다. 토양의 hydrophilic polymer의 농도에 따른 토양용적수분 함량은 강수량과 상관없이 2.5%이상의 hydrophilic polymer 처리구에서 97%~98%로, 100%에 가까운 토양용적수분 함량을 보였다. 강우 후 27일 동안 토양용적수분함량이 대조구에서 50%~60%를 보인 반면, 1.0%의 hydrophilic polymer 처리구에서는 70%~80%로 약 20%가 증가되었다. 식물생육을 조사한 결과, 황금줄사철나무와 통보리사초는 2.5% 처리구에서 가장 생육이 좋았고, 눈향나무는 1.0% 처리구, 좀보리사초는 0%(대조구)에서 생육상태가 가장 양호하였다. hydrophilic polymer 1.0% 처리구와 2.5% 처리구에서는 모든 식물이 생존하였으나 5.0%와 10.0%의 처리구에서는 식재 후 3개월 이내에 모두 고사하였다. 이는 hydrophilic polymer 배합비는 수종별 특성에 따라 다르게 적용되어야 함을 보여준 결과라 할 수 있다.