Borch, K.; Brown, K.M.; Lynch, J.P.


HortTechnology, Volume 8, Issue 4, p.575-579 (1998)

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Bedding plants are frequently exposed to water stress during the post-production period, resulting in reduced quality. It was shown that alumina-buffered P fertilizer (Al-P) provides adequate but much lower P concentrations than those conventionally used in soilless mixes. In a greenhouse study, impatiens ( Impatiens walleriana cv. Impulse Orange) and marigold ( Tagetes patula cv. Janie Tangerine) plants were grown in peat (washed to remove P) amended with two P-charged alumina (Al-P) treatments (3.05 plus or minus 0.2 and 9.26 plus or minus 1.5 micro M P); control plants received high P (1.5 mM P supplied by NH 4 H 2 PO 4 ). In plants grown with reduced P using Al-P, P leaching was greatly reduced and plant quality was improved. Diameter of impatiens plants and leaf area of plants of both species were reduced by Al-P. Marigold plants grown with Al-P had more flowers and fewer wilted flowers. Flower wilting was also reduced for impatiens plants grown with Al-P. In marigold plants, roots were confined to a small volume beneath the drip tube in control plants, while roots of Al-P plants were well distributed through the medium. There was no obvious difference in impatiens root distribution. When plants at the marketing stage were exposed to drought, the Al-P plants of both species wilted more slowly than the conventionally fertilized controls. The reduced leaf area in both species and the improved root distribution of marigold may account for the improvement in drought tolerance of the Al-P plants.