A method of producing lignin-based matrix microparticles for the controlled release of an agricultural active includes forming an emulsion of an organic solution in an aqueous solution, wherein the organic solution contains a lignin derivative and an agricultural active in a volatile organic solvent and the aqueous solution contains an emulsifier; and removing the organic solvent, thereby producing microparticles having a matrix comprising the lignin derivative within which the agricultural active is distributed. Small, spherical lignin-based matrix microparticles that release an agricultural active at a controlled rate are described, as are plants and plant propagation materials that are treated with such microparticles.