Do another soil test. Don't add anything to your soil (aside from mulch) without knowing exactly what deficiencies it has.

Many yellow conifer cultivar propagules become less yellow with age, in the same fashion as some dwarf forms often becoming more vigorous in time. If that is the case in this instance perhaps tinkering with the soil chemistry will not produce an effect.

A magnesium deficiency is typically characterized by a chlorosis or yellowing of the foliage, beginning with the lower, older growth and then progressing to the younger leaves. With conifers, this deficiency usually shows up as a yellowing of the tips of the needles.

To my knowledge, there is no basic plant nutrient that intensifies gold or yellow foliage in those plants that are bred for that effect - that characteristic is in the genetic make-up of the plant. It is far more likely that it will be a typical green plant that is showing the effect of a nutrient deficient by yellowing......as described above. A number of different plant nutrients can have that effect, if lacking.

...AND, to add to what GG48 said, magnesium needs to be in the right proportion to calcium or else the uptake of one or the other is inhibited.

Like the unpro said, do a soil test.

tj

EDIT: I recall mg being suggested for helping with BLUE conifers. It did work for me with Pseudotsuga menz. 'Dandy Doug' and, no I didn't do a soil test first. Do as I say, not as I do. ;-)

This post was edited by tsugajunkie on Wed, Mar 26, 14 at 18:50

Realize too, manganese (not magnesium) is yet another trace nutrient, the shortage of which can induce chlorosis in certain plants. Red (rubrum) maple is the classic example of this condition. Ken, I know of nothing to purposely foment yellowing on your pines.

+oM