102 A YEAR IN AGRICULTURE 



resulting in their conservation. A study of soil fertility, 

 therefore, must keep constantly before us the theme of con- 

 servation wisely using and making permanent the fertility 

 of the soil for all future use. To restore a depleted soil to 

 high productive power in economic systems of agriculture 

 requires education and skill. 



Elements of plant-food. The farmer should be as familiar 

 with the names of the ten essential elements of plant-food as 

 he is with the names of his ten nearest neighbors. These 

 plant-food elements are just as necessary for the plant as 

 food is for animals. Agricultural plants consist of ten ele- 

 ments. Not a keniel of corn, grain of wheat, leaf of clover, 

 or spear of grass could be produced if the plant failed to 

 secure any one of these ten elements. Some of them are 

 supplied in abundance by natural processes; others are not 

 so -provided, and -the farmer must supply them or his land 

 becomes unprpdueti.ve. : 



- -The- ten elements that plants live on are carbon, hydrogen, 

 oxygen, phosphorus, potassium, nitrogen, sulphur, calcium, 

 iron, and magnesium. Two elements, carbon and oxygen, are 

 contained in the air in the form of a gas called carbon diox- 

 ide, and this compound is taken into the plant through the 

 thousands of breathing pores upon the leaves. Hydrogen is 

 one of the elements of which water is- composed. Water is 

 taken into the plant through the roots, carried through the 

 stem to the leaves, and there, under the influence of chloro- 

 phyll, sunlight, and life-principle, the carbon, oxygen, and 

 hydrogen are made to unite into important plant compounds, 

 such as the sugars, later transformed into starch and fiber. 



