NATUBAL MANURES. 67 



Scotia plaster is purer than that obtained from New 

 York. The New York plaster, however, frequently con- 

 tains appreciable amounts of phosphoric acid. 



Salt. — Common salt is sometimes used as a manure. 

 It supplies no essential plant-food constituents; and its 

 value is still a disputed point, though it is admitted 

 that, where its use is favorable, it is due 'to indirect 

 action in aiding the decomposition of animal and vege- 

 table matter, increasing the absorbing power of soils, and, 

 by its reaction with lime, acting as a solvent for phos- 

 phates. Salt is frequently applied in connection with 

 nitrate of soda for wheat crops, to prevent a too rapid 

 growth of straw. 



The Application of Lime. — The quantity of lime to 

 be applied may vary according, to circumstances ; heavy 

 lands, rich in organic matter, may receive more, and 

 lighter lands, less. The usual amount in the Eastern 

 States, on average land, ranges from one to three tons 

 of quicklime per acre. This is applied once in six or 

 seven years, the application of small quantities being 

 frequently more useful than large quantites applied at 

 wider intervals. Lime should be applied on the surface, 

 as its tendency is to work into the soil, and gradually 

 get below the surface soil. The time of application, 

 also, varies with the kind of crop and the character 

 of the soil. For pasture-lands or mowing-fields, the 

 early spring or fall are the best seasons to apply it. 

 It should never be used directly with commercial fertil- 

 izers containing ammonia and soluble phosphoric acid, 

 as it sets free the ammonia, and reduces the solubility 

 of the phosphates. 



