Abstract

With more refined methods of chemical analysis and experimentation, a larger number of elements has been found in recent years to be essential for the healthy growth of plants than was previously supposed. Attention has also been focussed on the infertility of soils due to deficiencies of the so-called minor or trace elements. Plants in general need about a dozen elements for proper growth. These may be grouped into (a) the primary major elements consisting of nitrogen, phosphorus and potassium; (b) the secondary major elements like calcium, magnesium and sulphur; and (c) minor elements consisting of iron, manganese, boron, zinc, copper and molybdenum. This last group is needed only in very low concentrations, varying from half to 400 parts per million of the nutrient solution. The terms major and minor are not to be taken as referring to the relative value of these elements to plants, since all are essential, but only as indicating the relative quantities needed by the plant. It would seem preferable to use the term "trace elements" in place of the term minor elements, as less liable to cause confusion.

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