2019 ASHS Annual Conference

As the fresh water is also limited in Hong Kong, the Hong Kong government tried to solve the problem. In the 1960s when the Hong Kong government began to import raw water from Dongjiang (the East River) from neighboring Guangdong province. Currently, around 70-80% of our fresh water comes directly from Dongjiang. According to the government record in 2017, the costing of import raw water from Dongjiang is 14. 4 billion Hong Kong dollars per 3 year (~4.4 billion Hong Kong dollars per year).

This project aims to study water conservation for irrigation of urban ornamental plants in Hong Kong. Nearly all the horticulture and landscape maintenance contracts in Hong Kong are mentioned that the plants should be daily watering with 100mm to 150mm deep. According to LCSD, the landscape area is over 1.5 million m² that is a large amount of water consumption (270 billion liters of water per year). If the watering has to be done bi-daily, it can satisfied the daily water consumption of 1.25 million families in Hong Kong. The value of the water is around 1.1 billion Hong Kong dollars per year.

In the experiments, the drought resistance of plant was investigated of the 12 species (Celosia argentea var. plumose, Duranta iorentzii, Arachis hypogaea, Lantana camara, Hibiscus rosa-sinensis, Liriope spicata, Ophiopogon japonicus cv.'Nanus' and Sphagneticola trilobata, Zoysia japonica, Axonopus compressus, Schefflera arboricola ‘Variegata’ and Rhoeospathaceo cv. Compacta ) which were urban ornamental plants in Hong Kong. During the experiment, the lifespan of those species under drought were collected (Fig. 4.6). The five species of Celosia argentea var. plumose, Duranta iorentzii, Arachis hypogaea, Lantana camara and Hibiscus rosa-sinensis had the shortest lifespan. They could not live over 6 days under the drought. The three species of Liriope spicata, Ophiopogon japonicus cv.'Nanus' and Sphagneticola trilobata could not live over 32 days under the drought. The two species of Zoysia japonica and Axonopus compressus could not live over 36 days under the drought environmental condition. Only the two species of Schefflera arboricola ‘Variegata’ and Rhoeospathaceo cv. Compacta had the longest lifespan. They could live over 2 months (80 days and 81 days) under the drought environmental condition.

The result in experiment 2, it proved the lifespan under drought environment can be affected by the soil volume and planting density. The result in experiment 3, the species in the two trials were longer than the estimated days from experiment 1. As the reason of the variety of plant habits, the trials with planting different species should extend their life under drought environmental condition.

In the part of questionnaire, it has contacted respondents by on-line questionnaire method, who worked in the related industry. There were altogether 77 persons who had completed the designed questionnaires. Basic information, opinion on watering plants as well as recommendations and suggestion were obtained from them. Those information, opinions and recommendations on the practice of plant watering were used to support the recommendation.

To conclude, the drought resistance of plant had the relationship with the origin of species, soil volume, planting density and variety of plant habits. After summarizing the results, the recommendations was covered the garden design, horticulture maintenance contract specification, front-line staff training and new technology. All the results were used to further prove the corn problem in some real case study.