Three species of woody plants, Ilex crenata 'Helleri', Juniperus chinensis procumbens 'Nana', and Ligustrum lucidum, were grown in one-liter containers filled with pine bark to determine Fe and Mn requirements with regard to rate and ratio. FeEDTA and MnEDTA were applied at either a 2:1 or 1:2 ratio of Fe:Mn at 5 concentrations each, 3 times per week with each irrigation. Medium solutions were collected every 21 days on one species and analyzed for Fe and Mn levels. Dry weight and tissue Fe and Mn levels were determined for all three species. Neither rate nor ratio of applied Fe and Mn had an effect on shoot dry weights. Control treatments, in general, had the lowest medium solution and tissue levels of Fe and Mn, however, there was no difference in dry weights between control and treatment plants. These results suggest that pine bark supplies adequate levels of Fe and Mn for growth under the conditions of this study. In a second study, three sources of Fe and Mn were applied to Tagetes erecta 'Inca' growing in 500 cc plastic pots containing sieved pine bark at 3 lime rates: 0, 3, and 6 kg m⁻³. Sources of Fe and Mn were pre-plant Micromax, liquid sulfate salts, and liquid chelates applied in the irrigation water. No difference in growth between micronutrient sources was detected, however, growth was greater at the 3 and 6 kg m⁻³ lime rates. Levels of Fe and Mn in medium solution and tissue decreased with increasing lime rate, with availability of Fe and Mn greatest with chelate as the source, regardless of lime rate. A similar study was conducted with a control and liquid sulfate treatment. There was no difference in dry weight between the sulfate treatment and the control, except at 0 kg m⁻³ lime where the control plants were larger. Again, lime additions increased growth, and Fe and Mn availability in medium solution and tissue levels decreased. These results suggest that if Fe and Mn additions are needed, all sources provide adequate Fe and Mn for growth.

M.S.