Achieving a precise fertilization program is very important in potted plant cultivation. This issue becomes more important in the use of slow-release fertilizers, which provide nutrients to the plant for a longer period. For this purpose, the effect of applying Fermocomplex, a slow-release fertilizer with an 18-11-12 S+Mg+TE formula, on the growth and development of geranium was investigated. The research was done in a completely randomized design and with the use of different amounts of fertilizer during three stages (planting seeds (seedling stage), transferring seedlings to pots (vegetative stage), and transferring plants to final pots until flowering (reproductive stage)) in a medium including 10% rice husk + 40% perlite + 50% peat moss. In the first stage, the treatments included 3, 6, and 9 kg m-3, and in the second and third stages, they included 0, 3, 6, and 9 kg m-3 of fertilizer. Based on the amount of fertilizer at each stage, the treatments were identified with three-digit codes, each number representing the amount of fertilizer. After 6 months of seed sowing, growth indices were measured, including plant height, leaf number, stem diameter, number of branches, fresh and dry weight of shoots and roots, number of flowers, and chlorophyll, nitrogen, phosphorus, and potassium content of leaves. Based on the results, different amounts of fertilizer caused significant differences in chlorophyll content and all growth indices except the stem diameter but did not affect the amount of leaf nitrogen, phosphorus, and potassium. The greatest plant heights (41.9 cm and 44.8 cm) were observed in the treatments with 3 kg m⁻³ across all three stages (treatment 3-3-3) and 9 kg m⁻³ in the first and second stages (treatment 9-9-0), respectively. Similarly, the highest number of inflorescences (9.3, 10, and 10.6) was recorded in treatments 3-3-0, 3-3-3, and 6-6-6, respectively. In general, plants that were fertilized in two or three stages, in most traits such as height, chlorophyll content, number of leaves, number of flowers, fresh and dry weight of shoot and root, were superior to plants that were fertilized in only one stage. The best growth was observed with the consumption of 3 kg m-3 fertilizer in all three stages (3-3-3 treatment), and a higher amount of fertilizer. |
