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In selecting a manufactured fertilizer for trees, the ordinary commercial brands made for farm use will serve, but some of the mixtures prepared expressly for shade trees are better, and probably worth the difference in price. The nitrogen-phosphorus-potassium ratios are usually printed on the bags in bold figures. Most formulas meant for crop tillage (5-10-5, 6-8-6, 10-10-10, and the like) are lower in nitrogen than are most tree formulas, which will run 10-8-6,10-6-4,or maybe 8-6-8. Most field f ertilizers come as finely divided powders intended to dissolve rapidly. Tree foods are milled in coarse granules for a slower, longer lasting effect. The better prepared tree foods incorporate at least some of the trace minerals, such as boron, magnesium, and manganese, which trees are now believed to require. |
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