Answer: Magnolias do prefer a somewhat acidic, humusy, evenly moist yet well drained soil. (Soil in your area is usually naturally acidic so that would not usually be something to worry about.) If the tree seems healthy overall and the foliage looks good, then it is not likely related to the growing conditions per se. A new tree will take several years to become established in its new location and then bloom up to its potential.
There might be some concern as to the siting of the tree. These deciduous early blooming magnolias form their flowerbuds the year before they open and hold them all winter, so one thing you can consider is how many flower buds were actually formed compared to how many open successfully. If the winter is severe or the tree is planted in an exposed windy spot, or if there are oscillating spring temperatures with frosts/freezes once the buds have begun to swell for the season, then the buds can be damaged and the bloom display diminished.
There is not much you can do to control the weather, so if this is what is happening then you will have to really enjoy the "better" years when they do come along. Even with just a few blooms this is a lovely tree.
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