268 BOARD OF AGRICULTURE. 



opinion as to what constituted a sustaining ration for any 

 given animal, and also as to the extent to which crops depend 

 upon the atmosphere. 



Without stopping now to review the state of agricultural 

 doctrine and practice, as it was twenty-five years ago in Ger- 

 many, or to trace in detail the steps of progress since trav- 

 ersed, I will state briefly some of the substantial advantages 

 that have been gained as the immediate outcome of the efforts 

 of the experiment stations. 



1st. In respect to the food of plants, it has been settled 

 that potash, lime, magnesia, iron, phosphoric acid, and sul- 

 phuric acid must be furnished to all agricultural plants 

 through their roots and by the soil, in order to their growth. 

 It has also been shown that soda, silica, and chlorine are not 

 needful for the early growth of grain crops, but that chlorine 

 is essential for the perfection of the seed, and that silica is 

 probablj^ necessary to uniform blossoming and ripening. It 

 is further proved that water must enter crops through their 

 roots ; that carbon, which constitutes more than half their 

 weight, is superabundantly furnished by air ; that air and 

 water together yield the materials out of which fully ninety 

 to ninety-eight per cent, of crops is built up ; and that the 

 soil has to give for their nourishment but the two to eight 

 per cent, of mineral matters which remain as ashes when 

 they are burned, and the one-half to two per cent, of nitro- 

 gen which they also contain. It is likewise definitely settled 

 that nitrates in the soil are the chief natui'al source of nitro- 

 gen, while the ammonia of manures, as well as a variety of 

 substances containing nitrogen, and found in urine or formed 

 in the decay of dead animals, likewise supply vegetation 

 with nitrogen. 



The experiment stations have further ascertained, by a 

 multitude of trials, what quantities and proportions of all 

 these elements are needful to produce any given crop, and to 

 what extent they are removed from the soil. On the other 

 hand, it has been determined what kinds of plant food, and 

 what quantities, are contained in the long list of manures and 



