2017 ASHS Annual Conference

Kale (Brassica oleracea L. subsp. acephala) is valued for its health promotion phytochemicals, which can be influenced by genotypic, environmental and production factors. A greenhouse pot-experiment was performed to determine the effects of different types of natural growing medium amendments on kale plant tissue mineral nutrients content. The types and rates of amendments were 47.5 g potassium humate/pot; 50 g dry vermicasts/pot; and 100 g volcanic minerals/pot mixed in Pro-mix BX™ soilless potting medium. The control was the Pro-mix BX™ alone. Comparatively, the electric conductivity (EC) of the dry vermicasts (8.86 mS/cm) prior to mixing in the potting medium was the highest followed by the potassium humate treatment with 2.35 mS/cm. The least EC of ≤0.67 mS/cm was recorded for the volcanic mineral and the Pro-mix BX™ alone. Similarly, the dry vermicasts contained the highest nitrogen content of 30.2 mg/g followed by 9.7 mg/g for the potassium humate. Calcium content was lower in the dry vermicasts (33.1 mg/g) as compared to the volcanic mineral (228.0 mg/g), and the least in the other treatments. Kale plant tissue nutrients content varied similar to the nutrients content of the amendments, but there was no association between the two. Generally, plants grown in the dry vermicasts amended medium recorded the highest total nutrients content. These included nitrogen, phosphorus, potassium, magnesium and boron at 36.6, 6.2, 33, 4.3 and 233 mg/g, respectively, and were greater than the Pro-mix BX^TMcontrol by 51, 90, 88, 77 and 61%, respectively. Iron and zinc contents were similarly high for plants grown in volcanic mineral and the Pro-mix BX™ alone i.e. 0.12 and 0.17 mg/g respectively, as compared to the other treatments. This initial work suggested that the type of natural amendment can determine the functional nutrient properties of kale, which is currently under investigation.

Keywords: kale, organic vegetable, vermicompost, volcanic minerals, humic acid, tissue nutrient