PLANT FEEDING. 5 



and two tons of dry straw, how many pounds of soil ma- 

 terial have been removed? 



The three important elements. As a rule all the soil 

 elements essential to the growth of plants, except nitro- 

 gen, phosphorus and potassium, are abundantly present 

 in the soil. These are therefore the only ones with which 

 the farmer is seriously concerned in the feeding of his 

 plants. The problem of fertilizing the land demands 

 a careful study of these three very important elements. 



6. How much nitrogen is removed from the soil in 

 one ton oi shelled corn? How much phosphoric acid? 

 How much potash? 



WHEAT ■ 

 CORN ■ 



BUTTER 



When a Ton Is Sold. 

 The relative amounts of plant food removed when a ton of each product is 

 sold is indicated in the sketch. 



