Submitted to: HortScience
Publication Type: Abstract only
Publication Acceptance Date: 3/14/2007
Publication Date: 7/14/2007
Citation: Taylor, M., Nelson, P., Frantz, J. 2007. Impact of low iron and phosphorus stresses on acidification of nutrient solution by geranium (pelargonium x hortorum bailey). HortScience. Scottsdale, AZ, July 16-19, 2007. Interpretive Summary:
Technical Abstract: The cause of sudden substrate pH decline by geranium is unknown. Low Fe and low P have been shown to cause many plant species to acidify the substrate. Research was done to determine if low Fe or P stresses caused 4 geranium (Pelargonium x hortorum Bailey) cultivars to acidify nutrient solution. Two cultivars were susceptible and two resistant to substrate acidification based on a grower survey. Rooted geranium cuttings were transferred to 4L containers containing modified Hoagland’s solution with N supplied as 15% NH4 and 85% NO3. The plants were grown in a greenhouse for 44 days. Treatments consisted of a complete nutrient solution and two similar solutions devoid of either Fe or P. Solutions pH was set at 5.8, changed weekly, and tested 3 and 6 days after each change. Since all cultivars showed similar responses, results were combined. Twenty days after transplanting (DAT) plants in all treatments, including control, caused solution pH to fall below 5. At 37 DAT solution pH levels for control, minus Fe, and minus P treatments were 4.1, 3.7, and 3.6, respectively. Results indicated that geranium is an acidifying plant when N is supplied as 15% NH4 and 85% NO3. Additionally, low Fe and low P stresses increase the acidification rate. Total dry weights of minus P plants were about half that of minus Fe plants. This indicated that plants under P stress had a higher specific rate of acidification than plants under Fe stress.