Calcium and magnesium requirements of Ilex crenata Thunb. "Helleri"

Abstract

Rooted cuttings of Ilex crenata 'Helleri' were grown in sand culture with four rates of Ca and Mg (0, 5, 10, and 40 ppm) in a factorial experiment. No increase in total dry weight was achieved by increasing Ca and Mg rates above 5 ppm. Necrosis of shoot apices occurred at the 0 ppm Ca rate. A second rate experiment supported the results of the initial research. In addition to symptoms of Ca deficiency on the 0 Ca treatments, symptoms of severe Mg deficiency appeared on the 0 Mg treatments. These began as a discoloration of the lower leaves followed by abscission. A third experiment was performed on 'Helleri' holly growing in pine bark. Calcium was supplied at 0 and 120 ppm and Mg at 0 and 60 ppm. No differences in dry weight were observed. A third experiment studied the influence of four dolomitic limestone rates (0, 2, 4, and 8 kg/m³) and two gypsum rates (1 and 2 kg/m³) mixed with pine bark on Ca availability, Mg availability, and pH over time. Although the addition of dolomitic limestone increased Ca and Mg in the medium solution, unamended bark supplied sufficient quantities of both elements for the growth of Ilex crenata 'Helleri'. The addition of gypsum caused a large initial increase in Ca in the medium solution, but supplies dropped drastically thereafter.