The substances are called trace elements, of which only the smallest amounts are necessary for plant growth and which must not be missing in the soil.
In addition to the main- or core nutrients, the vegetable plants need a whole range of other nutrients, z.B. Bor, Brom, Chlor, Eisen, Iodine, copper, Mangan, Magnesium, molybdenum, Sodium, sulfur and zinc. They are needed in such small quantities, that they are mostly ignored when fertilizing. They are usually present in sufficient quantities in any weathered soil. However, since the different types of vegetables draw on one or the other element to varying degrees, Complete fertilizers have been developed, which take this into account and contain the most important trace elements. Magnesium occupies a certain special position among the trace elements, as almost all types of vegetables require mg to a greater or lesser extent. Magnesium is involved in the structure of leaf green and has a major influence on substance production. One should therefore potash containing magnesium- and prefer lime fertilizer.