The basic slag is

Solution(By Examveda Team)

The basic slag is Citrate soluble fertilizers.
Basic slag is a dark powder that is insoluble in water and does not cake. It contains not less than 14 percent P₂O₅ in citrate-soluble form. Basic slag is most suitable for use on acid soils as a base fertilizer.
Basic slag is a by-product of the steel industry. In the steelmaking process the impurities in the crude iron are oxidized and together with lime form the slag. This slag which contains the phosphorus in the form of silicophosphates is ground to a fine powder.