Growth Response of Kale ‘Ripbor’ to Different Growing Medium Conditioners

Kale (Brassica oleracea L. subsp. acephala) is considered a high-value crop based on its phytochemicals and health benefits. Consumers’ demand for organic and high-value natural foods is increasing due to increasing food safety and environmental concerns. A pot experiment was carried out to determine the response of kale ‘Ripbor’ plants to K-humate (47.5 g/pot), volcanic minerals (100 g/pot) and dry vermicasts (50 g/pot). The control treatment was Pro-mix BX™ potting mix alone. Only the pH of the dry vermicasts was within the acceptable limits for most plant between 5.7 -7.5. The relative growth rates of plants grown in the dry vermicasts (192 mg dry weight/day) was significantly (P<0.05) the highest as compared to approximately 600 mg dry weight/day for plants grown in either the K-humate or volcanic mineral amended medium. Total plant fresh weight yield did not significantly (P>0.05) differ among the three treatments. The dry vermicasts significantly (P<0.05) reduced leaf and stem mass densities by more than 30% as compared to the mean densities for the other three treatments including the control treatment. Additionally, leaf dry-matter content was increased by 29% in the K humate, volcanic minerals or Pro-mix BX™ as compared to the dry vermicasts. Leaf tissue N and protein contents were 43% higher in plants grown in the dry vermicasts than in the other treatments. The N and protein contents of the control plants were the least. The results suggested that the dry vermicasts provided suitable growing medium conditions, which led to higher growth response of the kale plants as compared to the volcanic minerals and the K-humate treatments.

Keywords: Conditioners, amendments, volcanic minerals, vermicasts, potassium humate, high value crop