Growth and flowering in Petunia hybrida, Callistephus chinensis and Impatiens balsamina inoculated with mixed AM inocula or chemical fertilizers in a soil of low P fertility

Three seasonal ornamental plants, namely Petunia hybrida, Callistephus chinensis and impatiens balsamina. were tested for their response to inoculation with mixed indigenous AM culture when grown on a marginal wasteland amended with organic matter. Subsequently, the treatments consisting of AM inoculations were compared with those consisting of recommended chemical fertilizers in terms of growth response and cost economics. In all the three plant species, mycorrhizal inoculation led to marked improvement in both reproductive (number of flowers) and vegetative (dry matter) phase of the plants. P. hybrida showed a threefold increase over uninoculated plants in the reproductive growth as compared to twofold in C, chinensis and I. balsamina. Application of the recommended dose of chemical fertilizers produced a comparable response. The inoculated plants produced greater dry matter, grew taller, flowered at least 15 days earlier and produced more flowers when compared to uninoculated plants. In addition there was a significant increase in P and K uptake in shoots of all the three ornamentals. AM inoculation could be at least 30% cost economic as compared to the chemical fertilizers. Therefore, mycorrhizal inoculation is recommended at the nursery level for nutrient-deficient soil conditions because it is a cost-effective substitute for chemical fertilizers, either partly or fully, which makes the approach particularly suitable to marginal fanners with their low-input farming system. (C) 2000 Elsevier Science B.V. All rights reserved.