Effects of mix composition, fertilization, and pH on citrus seedlings grown in several U.C.-type potting mixtures in containers were studied over a 5-year period. The mixtures, consisting of fine sand, sphagnum peat moss, and redwood shavings consistently produced greater growth than did a mix containing clay loam, fine sand, and peat moss. Copper deficiency, often encountered in plants grown in soils and soil mixtures containing peat, could be prevented by the addition of CuSO₄ to the mixtures. Availability of other micronutrients to the plants appeared to be influenced primarily by soil pH which could be changed by varying materials used in the added fertilizer solution. When the soilleachate pH was higher than approximately 7.0, plants exhibited more micronutrient deficiency leaf patterns and made less growth.

The system which evolved as a result of these experiments has been tried with marked success in one large-scale greenhouse operation which previously had experienced difficulty in producing vigorous citrus seedlings free of nutrient-deficiency symptoms.