Abstract: The invention is directed to the fumigation of soils, enclosed spaces, agricultural products and other commodities, etc., using compositions which decompose to form carbon disulfide and certain other biocidal materials. Such fumigation can be used to control bacteria, fungi, insects, nematodes, rodents, and weeds.Fumigant compositions are described herein as "thiocarbonates," including, without limitation, salts of trithiocarbonic acid and tetrathiocarbonic acid, compositions having empirical formulae intermediate to these acid salts (such as MCS.sub.3.7, wherein M is a divalent metal ion), and compositions containing substances in addition to thiocarbonates [such as a stabilized ammonium tetrathiocarbonate which contains ammonium sulfide, i.e., (NH.sub.4).sub.2 CS.sub.4.(NH.sub.4).sub.2 S].The compositions are generally water soluble and can be prepared, stored, and used in aqueous solutions.