The effect of various iron-containing fertilizers on growth and propagation of Gladiolus grandiflorus

Plants of Gladiolus grandiflorus 'Friendship' were grown on a CaCO₃-containing soil treated with the following soil-applied Fe fertilizers: (1) self-produced Fe-enriched peat (Bar-Teva 55); (2) Fe-enriched ammonium polyphosphate (APP); (3) FeEDDHA (sequestrene 138). Foliar application of FeSO₄ solution in the presence of a wetting-agent (L-77) was also tested. Bar-Teva 55, FeEDDHA and FeSO₄+L-77 were found to be effective in the prevention of chlorosis, while APP was not. About 95% of the Bar-Teva 55-treated plants flowered, compared to 79-89% for the other treatments. Flowering in Bar-Teva 55-treated plants started a few days earlier. None of the fertilizers affected inflorescence stem length or the post-harvest keeping-quality of the flowers. With the exception of APP, the fertilizer treatments improved daughter corm growth. The number of cormels per corm in the Bar-Teva 55-treated plants was markedly higher than in other treatments. FeEDDHA and FeSO₄+L-77 treatments also increased cormel number per corm when compared to APP-treated plants and control. Effective Fe-containing fertilizers seem to be of great importance to flowering, corm growth and cormel formation. Fe-enriched peat was found to be the most efficient fertilizer among the ones tested.