The Analysis ok Fi:rtilizkr.s. 279 



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

 needful for the early growth of grain crops, but that chlo- 

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

 is probably necessary to uniform blossoming and ripening. 

 It is farther proved that water must enter crops through 

 theii^roots; that carbon, which constitutes more than half 

 their weight, is superabundantly furnished by- the 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 

 or eight per cent, of mineral matters which remain as ashes 

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

 nitrogen which they also contain. It is likewise definitely 

 settled that nitrates in the soil are the chief natural source 

 of nitrogen, 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 veg- 

 etation with nitrogen." 



All the earthy ingredients of plant food must be present in 

 every productive soil, and chemical analysis has shown that the 

 majority of these are so abundant that so far as they are 

 concerned the soil is inexhaustible. Some however are 

 found in our ordinary soils in comparati"cly small quanti- 

 ties. It is noteworthy that most of the cultivated plants 

 require large quantities of calcium, potassium, phosphorus, 

 and nitrogen. Compounds of calcium are usually abundant 

 in the soil, the others are there in limited quantity. The 

 compounds of potassium, phosphorus, and nitrogen are 

 drawn away rapidly by cultivation. In rare cases soils will 

 yield year after year undiminished crops. But these are the 



