28 Practical Farming 



their green leaves from the carbon dioxide in the air. 

 Hydrogen, when combined with oxygen, makes water, 

 which is of such vital importance to plant and animal life 

 alike. The water that plants take up from the soil by 

 means of their root system furnishes them with the greater 

 part of the oxygen they need and with all the hydrogen; 

 and from combination of it with the carbon taken in by 

 the leaves the plant makes starch, sugar, and woody 

 material for its structure and for storage as future food. 



Sulphur occurs in the soil in the form of 

 Occurrence sulphates of iron, lime, and magnesiimi. 



of Sulphur, rpj^^ sulphates and oxide of iron color our 

 Cnlorme, and ^ 



Phosphorus clays and play an important part m the man- 

 ufacture of the leaf-green of chlorophyll in 

 plants. Iron is the most plentiful of all metals and one of 

 the most essential plant foods, for without iron there would 

 be no green leaves and hence no getting of carbon from 

 the air, and therefore no plant growth. It exists in inex- 

 haustible amount in all cultivable soils, and while of vital 

 importance there is no danger that it will ever become 

 deficient, for the decay of the forest leaves and vegetable 

 matter in general rapidly restores it to the soil. 



The element chlorine is found in its most common 

 combination in the chloride of sodium, or common salt. 

 It is also found naturally combined with potash, and thus 

 furnishes one of the readiest means for restoring potash 

 to soils that are deficient in this material. While salt is 

 found in all soil waters and in all plants it is still an unset- 

 tled question as to whether or not it is an essential part 

 of plant food. Potash, with which chlorine is often com- 

 bined, is essential to plant life; but there is no evidence 



