335 



CHjiPTER XII. 



COMMON SALT, NITRATE OF SODA, SALTS OF AMMONIA, 

 GYPSUM, LIME. 



Efiect of these substances as elements of food ; their effect on the condition 

 of tlie soil — Kuhlmann's experiments with common salt, nitrate of soda, 

 and salts of ammonia; experiments with the same suhstances 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 gi-owth of plants — Experiments by 

 rincus with gypsum and sulphate of magnesia on clover ; decrease of 

 flowers and increase of stem and leaves of clover by sulphates ; the ci'op 

 is not in propoi-tion to the quantity of sulphates used — Efiect of gypsum 

 not yet explained ; indication in the comportment of clover soils vnih 

 solution of gyjisum ; 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 iii 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 tlie field. This influ- 

 ence is not always clear to our minds, but it is not less 

 certain. 



We have every reason to believe that wliere the crops 

 are increased by manuring with common salt alone, or 

 when the favourable influence of salts of ammonia or nitrate 



