Root-zone cooling affects growth and development of paprika transplants grown in rockwool cubes

The possibility of improving the efficiency of transplant production during a summer season was studied by applying partial cooling of the root-zone during the cultivation of paprika transplants in a greenhouse. Paprika seedlings produced in a closed transplant production system were transferred to rockwool cubes, and cool-water circulation systems using plastic and stainless pipes were tested in a greenhouse during a summer season. The root-zone temperature of rockwool cubes and growth and development of paprika transplants as affected by root-zone cooling were investigated. When plastic pipes were used, the cooling efficacy by circulation of cool water (17°C) was the greatest and the temperature of rockwool cubes decreased by 3.6°C during the day time on a sunny day. Partial cooling of the root-zone enhanced root growth and increased number of flowers as compared with the transplants grown on uncooled rockwool cubes. The results indicate that partial cooling of the root-zone can alleviate damages to transplants commonly caused under high air temperature conditions, which could efficiently improve the paprika transplant production efficiency in greenhouses during the summer season.