RATIO OF CALCIUM TO MAGNESIUM INFLUENCES BIOMASS,ELEMENTAL ACCUMULATIONS,AND PIGMENT CONCENTRATIONS IN KALE

Producers use elemental ratios, such as calcium (Ca): magnesium (Mg), in fertility programs to ensure sufficient nutrient uptake. Kale (Brassica oleracea L. var. acephala D.C.) accumulates high levels of carotenoids which can be beneficial for human health. Objectives were to determine the influence of Ca:Mg fertilization on 1) biomass, 2) essential nutrients, and 3) carotenoids in kale leaf tissues. ‘Redbor’ kale was greenhouse-grown in solution culture. Ca:Mg ratio treatments were 9:1, 6:1, 3:1, 1:3, 1:6, and 1:9. Ca:Mg ratio significantly affected biomass, nutrient accumulation, and carotenoids. Plant biomass decreased linearly (P ≤ 0.001) and β-carotene, lutein, neoxanthin, and antheraxanthin all increased, then decreased quadratically (P ≤ 0.001) as the ratio of Ca:Mg changed from 9:1 to 1:9. Ca:Mg ratio also affected leaf tissue Ca, Mg, potassium (K), sulfur (S), boron (B), manganese (Mn), molybdenum (Mo) and zinc (Zn). Results indicate that producers wishing to maximize elemental uptake and carotenoid content of kale need to consider the ratio of Ca:Mg in their fertility programs.