NATURAL MANURE. 25 



"Assuming," said the Doctor, who is fond of an argument, 

 " that the above statement is true, let us look at the facts. An 

 acre of soil, 12 inches deep, would weigh about 1,600 tons; and if, 

 as the writer quoted by the Deacon states, the soil contains 4 ozs. 

 of potash in every 100 Ibs. of soil, it follows that an acre of soil, 

 12 inches deep, contains 8,000 Ibs. of potash. Now, potatoes con- 

 tain about 20 per cent of dry matter, and this dry matter con- 

 tains, say, 4 per cent of ash, half of which is potash. It follows, 

 therefore, that 250 bushels of potatoes contain about 60 Ibs. of 

 potash. If we reckon that the tops contain 20 Ibs. more, or 80 

 Ibs. in all, it follows that the acre of soil contains potash enough 

 to grow an annual crop of 250 bushels of potatoes per acre for one 

 hundred years." 



"I know farmers," said Charley, "who do not get over 50 

 bushels of potatoes per acre, and in that case the potash would 

 last five hundred years, as the weeds grown with the crop arc left 

 on the land, and do not, according to the Deacon, exhaust the 

 soil." 



" Good for you, Charley," said the Doctor. " Now let us see 

 about the phosphoric acid, of which the soil, according to the 

 above statement, contains only half as much as it contains of pot- 

 ash, or 4,000 Ibs. per acre. 



" A crop of wheat of 80 bushels per acre," continued the Doc- 

 tor, " contains in the grain about 2G Ibs. of ash, and we will say 

 that half of this ash is phosphoric acid, or 13 Ibs. Allowing that 

 the straw, chaff, etc., contain 7 Ibs. more, we remove from the soil 

 in a crop of wheat of GO bushels per acre, 20 Ibs. of phosphoric 

 acid, and so, according to the above estimate, an acre of soil con- 

 tains phosphoric acid to produce annually a crop of wheat and 

 straw of 30 bushels per acre for two Jiundred years. 



" The writer of the paragraph quoted by the Deacon," continued 

 the Doctor, " selected the crops and elements best suited to his 

 purpose, and yet, according to his own estimate, there is sufficient 

 potash and phosphoric acid in the first 12 inches of the soil to 

 enable us to raise unusually largo crops until the nc<;t Centennial 

 in 1970. 



" But let us take another view of the subject," continued tne 

 Doctor. " No intelligent farmer removes all the potatoes and 

 tops, all the wheat, straw, and chaff, or all the corn and stalks from 

 his farm. According to Dr. Salisbury, a crop of corn of 75 bush- 

 els per acre removes from the soil 600 Ibs. of ash, but the grain 

 contains only 46 Ibs. The other 554 Ibs. is contained in the stalks, 

 etc., all of y/hich are usually retained on the farm. It follows 

 



