subsidy(Any monetary grant made by the government to a private industrial undertaking or charitable organization, but especially one given to consumers or producers in order to lower the market price of some service or product and make it readily affordable to the public)
subsoil drainage(The removal of surplus water from within the soil by natural or artificial means, such as by drains placed below the surface to lower the water table below the root zone)
substitutability(character of a process or substance to be possibly substituded by a less harmful one; The capability of a substance of being replaced by another, for example sweeteners used in place of sugar; chemistry)