Abstract

Fraser photinia, ‘Plumosa Compacta Youngstown’ juniper and ‘Hino-Crimson’ azalea were grown in pine bark amended with a factorial combination of five rates (0, 0.9, 1.8, 3.6 and 7.2 kg/m³) (0, 1.5, 3, 6 and 12 lbs/yd³) of olivine, a magnesium ortho silicate containing 27% Mg and four particle sizes of olivine. Calcium carbonate (38% Ca) at 2.4 kg/m³ (4 lbs/yd³) was incorporated into all olivine treatments. A separate treatment utilizing 4.2 kg/m³ (7 lbs/yd³) dolomitic limestone (22% Ca, 11% Mg) was also included to serve as a comparison to dolomitic limestone. In general, Mg concentration in the media increased with increasing olivine rate and decreasing particle size. Media P, K and Ca concentration and pH were not affected by olivine rate or particle size, nor were they significantly different from the treatment containing dolomitic limestone. Foliar Mg increased with increasing olivine rate in all species. Foliar K decreased with increasing olivine rate for ‘Hino-Crimson’ azalea and Fraser photinia. Top dry weight of ‘Plumosa Compacta Youngstown’ juniper was not affected by olivine rate or particle size while top dry weight of ‘Hino-Crimson’ azalea and Fraser photinia increased quadratically with increasing olivine rate, with the maximum occurring at 0.9 kg/m³ (1.5 lbs/yd³) and 1.8 kg/m³ (3.0 lbs/yd³), respectively. These maximum top dry weights were significantly heavier than plants grown with dolomitic limestone.