150 MANURES. 



PHOSPHORIC ACID. 



"We come now to the consideration of one of the 

 most important of all subjects connected with agri- 

 culture. 



Phosphoric acid, which forms about one-half of 

 the ashes of wheat, rye, corn, buck-wheat, and oats ; 

 nearly the same proportion of those of barley, peas, 

 beans, and linseed ; an important part of the ashes 

 of potatoes and turnips ; one-quarter of the ash 

 of milk, and a very large proportion of the bones of 

 animals, often exists in the soil in the proportion of 

 only about one or two pounds in a thousand, and 

 but a very small part even of this amount is in a con- 

 dition to be taken up by roots. The cultivation of 

 our whole country has been such, as to take away 

 the phosphoric acid from the soil without returning 

 it, except in very minute quantities. Every hundred 

 bushels of wheat sold contains (and removes perma- 

 nently from the soil) about sixty pounds of phospho- 

 ric acid. Other grains, as well as the root crops and 

 grasses, remove, likewise, a large quantity of it. It 

 has been said by a contemporary writer, that for each 

 cow kept on a pasture through the summer, there is 

 carried off in veal, butter, and cheese, not less than 

 fifty Ibs. of phosphate of lime (bone-earth) on an 

 average. This would be one thousand Ibs. for twenty 

 cows ; and it shows clearly why old dairy pastures 

 become so exhausted of this substance, that they will 

 often no longer produce those nutritious grasses 

 which are favorable to butter and cheese making. 



