"可溶性无机盐" can be translated into English as "soluble inorganic salts".
Here, "soluble" means capable of being dissolved, "inorganic" refers to substances not derived from living organisms or containing carbon-hydrogen bonds in a biological context (though in chemistry, it simply means not organic, i.e., not containing carbon-hydrogen bonds in the strict sense), and "salts" are compounds formed by the reaction of an acid with a base, typically consisting of cations and anions.