A surfactant composition for agricultural chemicals, containing fatty acid polyoxyalkylene alkyl ether expressed by the following general formula (I), R1CO(EO)m(PO)nOR2 (I) wherein the fatty acid polyoxyalkylene alkyl ether has a narrow ratio of 55% by mass or more, where the narrow ratio is expressed by the following formula (A): Narrow ratio=Σi=nMAX−2i=nMAX+2Yi (A).

Disclosed herein are mesocapsules that include agriculturally active ingredients. These mesocapsules are comprised of a polyurea shell and include hydrophilic groups on their surfaces and have a volume-average diameter of about 500 nm or less and some of them have a volume-average diameter on the order of about 300 nm or less. These mesocapsules are suited for delivering active ingredients that are not very soluble in water. Methods for making these mesocapsules include interfacial polycondensation reactions carried out in the presence of surfactants and other methods in which all or most of the surfactant is replaced by adding amino acids to the aqueous phase of the interfacial reaction mixture before forming the final emulsion.