PROBLEM TO BE SOLVED: To obtain a biologically active substance which has an elution rate not to extremely increase with following temperature rise even in the case of uses in a vinyl greenhouse cultivation and mulch cultivation liable to cause an extreme temperature rise, on the contrary, not to extremely decrease with following a low soil temperature even in the case of use in cultivation in a low-temperature period. SOLUTION: The coated biologically active substance is obtained by coating the surface of a biologically active substance particle with a polyurethane obtained by reaction between tripropylene glycol and an isocyanate.
