136 PRACTICAL FARM CHEMISTRY. 



paring these with the corresponding quantities re- 

 quired for the production of grain and potato crops, 

 we find them pretty large indeed; and clover there- 

 fore must be called the most exhausting crop that 

 the farmer grows. 



When we are told that clover is a " renovator " of 

 the soil, we would naturally feel inclined to ask: 

 What does it add to the soil? Its mineral consti- 

 tuents, among them the potash and phosphoric 

 aoid, cannot possibly be derived from any other' 

 source but the soil. Like other leguminous plants, 

 clover has the power of gathering and assimilating 

 free nitrogen from the atmosphere; but it cannot 

 possibly be enough to make up for the nitrogen 

 taken off in the hay. So we see that the famed 

 " renovator of soils " takes a good deal away, and 

 returns nothing but a portion of the removed nitro- 

 gen. Every two tons of clover hay harvested leave 

 the land poorer by ninety-three pounds of potash 

 and twenty-seven pound of phosphoric acid; and if 

 many such crops are taken off, without returning 

 these mineral elements in some form to the soil, it 

 is very plain that the latter must, in the end, lose 

 its fertility. 



This explains why clover will not grow on ex- 

 hausted land, especially on that which lacks potash, 

 for of that substance clover desires a considerable 

 quantity. It further suggests the usefulness of pot- 

 ash on land intended to be seeded to clover, but shy 

 to "take." 



While clover thus fails to add mineral elements 

 to the soil, its services as an "accumulator" of 

 available plant foods can hardly be appreciated too 

 highly. From soil and atmosphere it draws its 

 nourishment and stores it in its own tissues. The 



