Ever-bearing strawberry culture using a new aeroponic system with dry-fog spray fertigation during the summer
A new spray fertigation system (dry-fog hydroponics) was developed for establishing ever-bearing strawberry (Fragaria × ananassa Duch. 'Summer ruby') production during the summer. Dry-fog hydroponics is an aeroponic technique that sprays a very fine foggy nutrient solution with an average droplet diameter of less than 10 μm into the root zone. The roots extend into the chamber filled with dry-fog of the liquid fertilizer and absorb water and nutrients from the dry-fog that fills the rhizosphere. This aeroponic system needs less water than any other hydroponic technique and keeps rhizosphere temperature lower than air temperature owing to the release of latent heat by dry-fog evaporation and adiabatic expansion of solution from the exhaust nozzle. Runner seedlings of strawberry plants were cultivated with dry-fog aeroponic system from early June to December in a greenhouse, and the growth, flower bud formation, fruit quality, photosynthetic rates as well as the contents of chlorophyll and total soluble protein in leaves were compared with those of plants cultivated by drip fertigation with palm shell medium as a control. Rhizosphere and the crown temperatures of dry-fog aeroponics were reduced by approximately 3-5°C throughout the day compared with control and were maintained below 25°C during the late summer. Although ever-bearing strawberry plants are insensitive to high temperature under long day conditions from a viewpoint of flower initiation, low temperature, especially the crown part of shoot base, is considered important for inducing flowering. For dry-fog aeroponics, the number of inflorescences and °Brix of fruits significantly increased but the number of runners and vegetative growth significantly decreased compared with control. Photosynthetic rates of leaves grown with dry-fog aeroponics increased compared to those of the control under both light and CO2 limited and saturated measurement conditions. In addition, leaf chlorophyll and total soluble protein contents significantly increased in dry-fog aeroponics compared with the control. From these findings, we suggested that dry-fog aeroponics is a usable new hydroponics for raising ever-bearing strawberry plants during the summer by maintaining rhizosphere temperature low, and thus suitable for shifting their growth phase from vegetative to reproductive.
Kanechi, M., Hikosaka, Y., Fukuda, C. and Uno, Y. (2017). Ever-bearing strawberry culture using a new aeroponic system with dry-fog spray fertigation during the summer. Acta Hortic. 1176, 37-44
crown temperature, hydroponics, photosynthesis, root zone, soilless culture, sprayponics