280 FIRESIDE SCIENCE. 



and amount of food which the potato demands. A 

 field of potatoes yielding 300 bushels to the acre 

 will remove /rom the soil in tubers and tops at 

 least 400 pounds of potash ; also it will remove 150 

 pounds of phosphoric acid. Now these amounts 

 are very large, and show that the potato plant is 

 a great consumer of the two substances, and also 

 show that in order to restore our potato fields to 

 their former productive condition, we must sup- 

 ply phosphatic compounds and substances holding 

 potash in large quantities. For six or eight gener- 

 ations in New England our fathers have been ex- 

 hausting the soil, by removing these agents in their 

 potato and other crops, and we have reached a 

 time when the vegetable is starving in our fields 

 for want of its proper food. Our farmers have 

 found that new land gives the best crops, and this 

 is due to the fact that such fields afford the most 

 potash. But so long as we crop our pastures so 

 unreasonably, we cannot resort to new land, as 

 land is not new that has had its potash and phos- 

 phatic elements removed by grazing animals. A 

 potato field which gives but 100 bushels to the 

 acre requires at least 140 pounds of potash, but 

 by allowing the tops to decay upon the field, 60 

 pounds are restored to the soil again, as that amount 

 is contained in them. A medium crop of potatoes 

 requires twice as much phosphoric acid as a me- 



