_Potash marl_, such as is found in New Jersey, contains a large proportion of potash, and is an excellent application to soils requiring it. _Feldspar_, _kaolin_, and other minerals containing potash, are, in some localities, to be obtained in sufficient quantities to be used for manurial purposes. _Granite_ contains potash, and if it can be crushed (as is the case with some of the softer kinds,) it serves a very good purpose. SODA. [If applied in large quantities will it produce permanent injury? In what quantities should salt be applied to composts? To asparagus?] _Soda_, the requirement of which is occasioned by the same causes as create a deficiency of potash, and all of the other ingredients of vegetable ashes, may be very readily supplied by the use of _common salt_ (chloride of sodium), which consists of about one half sodium (the base of soda). The best way to use salt is in the lime and salt mixture, previously described, or as a direct application to the soil. If too much salt be given to the soil it will kill any plant. In small quantities, however, it is highly beneficial, and if _six bushels per acre_ be sown broadcast over the land, to be carried in by rains and dews, it will not only destroy many insects (grubs, worms, etc.), but will, after decomposing and becoming chlorine and soda, prove an excellent manure. Salt, even in quantities large enough to denude the soil of all vegetation, is never _permanently_ injurious. After the first year, it becomes resolved into its constituents, and furnishes chlorine and soda to plants, without injuring them. One bushel of salt in each cord of compost will not only hasten the decomposition of the manures, but will kill all seeds and grubs--a very desirable effect. While small quantities of salt in a compost heap are beneficial, too much (as when applied to the soil) is positively injurious, as it arrests decomposition; fairly _pickles_ the manures, and prevents them from rotting. [What is generally the best way to use salt? What is nitrate of soda? What plants contain lime?] For _asparagus_, which is a marine plant, salt is an excellent manure, and may be applied in almost unlimited quantities, _while the plants are growing_, if used after they have gone to top, it is injurious. Salt has been applied to asparagus beds in such quantities as to completely cover them, and with apparent benefit to the plants. Of course large doses of salt kill all weeds, and thus save labor and the injury to the asparagus roots, which would result from their removal by hoeing. Salt may be used advantageously in any of the foregoing manners, but should always be applied with care. For ordinary farm purposes, it is undoubtedly most profitable to use the salt with lime, and make it perform the double duty of assisting in the decomposition of vegetable matter, and fertilizing the soil. Soda unites with the silica in the soil, and forms the valuable _silicate of soda_.