Response of Kale to Single-Dose Application of K Humate, Dry Vermicasts, and Volcanic Minerals

Abstract

ABSTRACTWorldwide consumers are concerned about potential residue and persistence of harmful chemicals in the environment and on foods, especially leafy vegetables like kale, Brassica oleracea L. var. acephala (DC.) Alef. A greenhouse pot experiment was conducted to determine whether kale, cv. Ripbor, responded to different natural sources of growing medium amendments: 47.5 g K humate/pot; 50 g dry vermicastst/pot; or 100 g volcanic minerals/pot. Each of the amendments were individually added to 1 kg Pro-mix BX/pot with the Pro-mix BX alone as the control. Plant growth rate grown in dry vermicasts was highest. The fresh weight was higher due to volcanic minerals than for the control and values for K humate and dry vermicasts were similar to the control and volcanic minerals. The dry vermicasts reduced leaf and stem mass densities compared to other treatments. Leaf dry matter content was increased by approximately 29% in the K humate, the volcanic minerals, and the control compared to the dry vermicasts. SPAD values were higher in K humate and volcanic minerals than in other treatments. Amendment did not affect leaf fresh weight yield but was lower in the control. Percentages of N and protein were highest but the C:N ratio was lowest in plants grown in dry vermicasts. Overall, application of single-dose dry vermicasts resulted in the highest productivity compared to the other treatments.