2017 ASHS Annual Conference

Carbon dioxide (CO₂) supplementation is an important factor for optimal growth of ornamental plant in greenhouse. The objective of this study was to understand water and nutrient requirements of potted geranium (Pelargonium x hortorum L. ‘Pinto Premium Rose Bicolor’) under elevated CO₂ conditions. The study was conducted with three factorial treatments arranged in a split-split plot design. Two identical greenhouses were used and CO₂ was supplemented to maintain 1000 ppm in one of the greenhouses from 7 a.m. to 1:00 p.m. Plants in each greenhouse had moisture regimes of either 5, 10, or 15 cb, maintained by automatic tensiometer settings. Four nutrient levels of 0, 3, 6, and 9 g of 15N-9P-12K slow release granular fertilizer was used in each of the water treatments. A single potted plant was taken as one replication and 10 replications were made in each fertilizer treatment and the study was repeated. Height, width, the number of umbels, umbel width, number of flowers per umbel, photosynthesis, transpiration, stomatal conductance, and dry weight were recorded. The results showed that plants grown at elevated CO₂ had a higher rate of photosynthesis and higher dry weight. Plants grown at 10 cb moisture level at elevated CO₂ condition had the greatest number of flowers. Similarly, plants showed a higher rate of growth with increasing fertilizer rate in both elevated and ambient CO₂ conditions.