Effect of nutrient potassium: calcium: magnesium ration in the production of flue-cured tobacco

Abstract

In an outdoor trial with tobacco in sand culture, four potassium: magnesium ratios were combined with three calcium levels in the nutrient solution while the pH and total ionic concentration were maintained constant. By reduction of the concentration during ripening, the nitrogen regime was manipulated so as to produce plants closely resembling those in a held grown crop. Optimum leaf quality was found to result from the use of a nutrient solution containing 20-40 per cent of the cations as calcium on an equivalent basis. When calcium exceeded 40 per cent of the total cations, no good quality leaf was obtained ; when it formed only 20 per cent, the potassium : magnesium ratio had a less marked effect on quality. The concentrations of the three elements in the leaf of optimum quality are given for several leaf positions. At each leaf position the calcium content of the leaf was negatively correlated with quality. A potassium : magnesium ratio of 3:l in the nutrient led to quicker ripening of the leaf, and leaf thickness was dependent on the potassium : magnesium ratio of the nutrient.