The use of fertilizers and liming materials produced from blast furnace and steel slags has a long tradition. For example Thomasphosphate had been used for more than hundred years.
Silicate lime fertilisers (blast furnace lime and converter lime) are approved fertilizers in Germany since more than 60 and 30 years, respectively. They contain elements with useful properties for plant nutrition and soil quality.
Calcium and magnesium in slag have a better solubility than that of magnesium carbonate in natural limestone and dolomite. Both elements serve as plant nutrients and stabilizers for soil aggregates and their basicity increases or sustains soil pH.
The solubility of silicate from slag is often higher than from many other silicate containing soil improvers or rock powders. Silicate has beneficial effects on plant health, phosphate availability and soil structure. The content of trace elements like manganese, copper, zinc, boron or cobalt in slag satisfies both plant and animal demands.
Blast furnace lime has a mild effect on soil pH. Therefore, it is especially recommended for use on humus, sandy and peat soils. In addition, the high silicate and magnesium content which is readily available to plants promotes yields and plant qualities.
Converter lime from basic oxygen furnace slag as well as from ladle slag from the production of non-alloyed steel is suitable for all kinds of soils. It has a high neutralising value with prompt and sustainable effects on soil pH. The soluble silicate content and its reactivity increase the phosphate mobility in the soil and improve the efficiency of phosphate fertilisation.
Careful selection and processing of appropriate slag qualities ensures an effective activity in the soil.