Effect of Acidity and Cation Content of nutrient Supply on Yield of Pyrethrum (Chrysanthemum Cinerariaefolium)

Abstract

An acid medium, pH 5 to 6, was necessary for pyrethrum to attain maximum yield in sand culture. The lower the pH, the greater the concentration of calcium. required for maximum yield. The critical level of calcium was about 30 per cent of the total cations, i.e. somewhat higher than for other crops.

Plants supplied with low rates of calcium (1.6 to 3.2 m-equiv. per litre) were stimulated to flower earlier than plants supplied with higher rates, but soon died. Variations in acidity and calcium supply led to greater differences in yield during the first period of picking than during the second flush of flowering, and thus these factors are most important during establishment of the crop.