Effect of limited application of phosphorus on height and performance quality of geranium

To evaluate the effect of limited application of phosphorus (P) on height and performance quality of geranium (Pelargonium hortorum cv. Bulles Eye), an experiment was conducted in the greenhouse environment, based on completely randomized blocks design, during 2011-2012. Geranium seedlings were cultivated in the pots filled with peat-based substrate (80% peat + 20% garden loam soil (v/v)). Treatments were applied as four levels of nutrient solution (0.2 (control), 0.15, 0.1 and 0.05 mM P). At the end of the experiment, traits such as plant height, number and length of shoots, number of inflorescences, number of flowers in each inflorescence, pedicle length, fresh and dry weight of shoots and roots, number of leaves, leaf area, chlorophyll content of leaves, and leaf anthocyanin content were measured. According to the results, although the application of 0.05 mM P reduced plant height and length of the pedicles, but negatively affected fresh and dry weight of shoots and roots, chlorophyll content of leaves, and leaf number and leaf area, and the produced plants were not marketable. While, reducing the concentration of P in the nutrient solution from 0.2 to 0.1 mM, other than reduction of plant height, did not affect negatively other qualitative traits. Therefore, to achieve proper qualitative traits and reduce the consumption of P by geranium, limiting the application of P up to 0.1 mM is recommended