Effect of Potassium Fertilization on Growth, Flowering, Corms Production and Chemical Contents of Gladiolus hybrida, L. Cv. "Rose Supreme"

A pot experiment was conducted on Gladiolus hybrida cv."Rose Supreme" throughout the two successive growing seasons 2014 and 2015 in Antoniades Botanical Gardens, Horticulture Research Institute, Alex., Egypt to study the effect of potassium sulphate (48%K2O) foliar spray, applied at (1% and 2%) alone or combined with three percentages of the recommended (2g pot) soil amended potassium (50%, 75% and 100%), on growth, flowering quality and chemical constituents of gladiolus. Whereas, the control treatment was only, applying the complete percentage of the recommended soil amendment of potassium (100%). The results revealed that applying K foliar treatments significantly affected all the studied parameters compared to the control. The results indicated that applying 2% K foliar combined with 100% potassium soil dressing gave the highest significant values of plant height, number of leaves per plant, fresh and dry weight of leaves, number of florets per spike, floret diameter, spike length, fresh and dry weights of florets, new corm diameter, fresh weight and cormlets number per plant as well as leaf chlorophyll a and b contents and petals anthocyanins content. The results revealed that fertilizing the plants with 2% K foliar combined with 75% K as soil dressing advanced flowering dates by 4.47 days and 5.66 days than the control, for the first and second seasons, respectively. Also, it was also observed that applying 2% K foliar combined with 75% K as soil dressing had significant similar effects on floret diameter trait. The data also showed that, fertilizing the plants with 2% K foliar combined either with 100% or 75% K as soil dressing had similar effects on new corm diameter and fresh weight. Applying 2% K foliar combined with 75% K as soil dressing gave significantly superior anthocyanins content values than those obtained with fertilizing the plants with 100% K as soil dressing alone (the control). Regarding the effect of K foliar treatments on leaf nutrient contents, the results indicated that applying 2% K foliar combined with 100% potassium soil dressing gave the highest significant values of leaf N, proteins and P contents. Also, the results revealed that no significant differences were recorded due to applying 2% K foliar combined with 75% K as soil dressing and the control treatment for both of N and proteins contents. Whereas, the highest significant leaf K content values were recorded as a result of applying 100% K as soil dressing. The data revealed that the highest
significant values of leaf Fe, Mn and Cu contents (ppm) were recorded as a result of applying 2% K foliar combined with 100% K as soil dressing for both seasons. Also, fertilizing the plants with 2% K foliar combined with either with 75% or 100% K as soil dressing gave similar effects on leaf Fe and Mn contents. It can be concluded that when applying potassium sulphate as a foliar spray combined with potassium soil dressing, it has a potential effect on growth parameters. Also, potassium foliar spray can be used as a partial substitution of the recommended soil amended potassium for increasing nutrients uptake and thus stimulating growth and flowering characteristics of gladiolus hybrida cv."Rose Supreme".