CHAPTEE XII. 



COMMON SALT, NITKATE OF SODA, SALTS OF AMMONIA, 

 GYPSUM, LIMK. 



Effect of these substances as elements of food , their effect on the condition of the 

 soil Kuhlmann's experiments with common salt, nitrate of soda, and salts of 

 ammonia ; experiments with the same substances in Bavaria ; conclusions : 

 these matters are elements of food ; they are chemical means for preparing the 

 soil ; they cause the distribution of the food in the soil in the form proper for 

 the growth of plants Experiments by Pincus with gypsum and sulphate of 

 magnesia on clover; decrease of flowers and increase of stem and leaves of 

 clover by sulphates ; the crop is not in proportion to the quantity of sulphates 

 used Effect of gypsum not yet explained ; indication in the comportment of 

 clover soils with solution of gypsum ; such solution disperses potash and 

 magnesia in the soil Manures, their effect not explained by the composition of 

 plants produced by them Composition of the ash of clover manured with dif- 

 ferent substances Effect of lime ; experiments of Kuhlmann and Triiger ; 

 comportment of lime-water with soils. 



THESE salts are employed in agriculture in many 

 cases with marked success as manure ; and since 

 nitric acid, soda, ammonia, sulphuric acid, and lime, 

 are nutritive substances, the explanation of their efficacy 

 presents no difficulty. But they also possess other 

 peculiarities, by which they aid and promote the action 

 of the plough and of mechanical tillage, as well as the 

 influence of the atmosphere upon the condition of the 

 field. This influence is not always clear to our minds, 

 but it is not less certain. 



We have every reason to believe that where the 

 crops are increased by manuring with common salt 

 alone, or when the favourable, influence of salts of am- 

 monia or nitrate of soda is augmented by the addition 

 of common salt, the operation of the three salts essen- 

 tially depends upon their power of diffusing the nutri- 

 tive substances present in the soil, or of preparing those 

 substances for absorption. In what manner this takes 

 place with all is not yet explained. The first trust- 



