Plant-Food and Use of Fertilizers. 149 



twelve and even fourteen. At the very outside, of all the elements known to 

 •exist, only twelve or fourteen are necessary for plant growth. 



The plant food elements are as follows : Carbon, hydrogen, oxygen, nitrogen, 

 sulphur, phosphorus, clorine, potassium, calcium, iron, magnesium, silicon, sodium 

 manganese. 



Some authorities question the necessity of manganese and sodium. 



Carbon, Hydrogen and Oxygen make up the largest part of the woody struc- 

 ture of the plant, the carbohydrates and organic acids. 



^litrogen. Sulphur and also Carbon, Hydrogen and Oxygen are necessary for 

 the development of the proteid compounds in the plant. 



Phosphorus. — This element in the plant exists in the form of phosphates and 

 is found in all parts of the plant. It seems to have something to do with the 

 •development of the proteid substances in plants. Much phosphorus seems to be 

 necessary and it accumulates in the seed of plants. 



Chlorine. — The exact function of this element in plants is not definitely 

 Icnown. It is supposed by some authorities to have something to do with the 

 translocation of starch from the leaf to other parts of the plant. 



Potassium. — Compounds of this element are quite widely distributed in the 

 various parts of the plant. They seem to be necessary for the formation and 

 translocation of starch in the plant. Potash is always found in large quantities 

 in the ash of plants. 



Calcium. — This element in some form is found in all parts of the plant. 

 It always exists in large quantities in the ash of plants. Calcium seems to be 

 necessary for the growth of the cell structure, that is, for the formation of 

 cellulose out of starch which has been formed in the leaves. 



Iron. — Experiments have proved that iron in some form is absolutely nec- 

 essary for the deve.opment of chlorophyl, which is the green coloring matter in the 

 leaves of plants. In the absence of iron the leaves become yellow and even die, 

 due to the non-development of the chlorophyl grains. 



Magnesium. — This element seems to take part in the development of chlorophyl 

 in plants, and also has something to do with the translocation of prot 'd bodies 

 in the plant. 



Silicon. — It is still a mooted question as to whether this element is neces- 

 sary for plant growth or not. At one time it was supposed that this element gave 

 stiffness and strength to the stems of the plants, but this belief is being discarded. 

 It is believed by some that silicon helps in the development and formation of 

 seeds. 



Sodium and Manganese. — These elements are not supposed to perform any nec- 

 essary function in the growth of plants, even though they have generally been 

 classed with the plant-food elements. Manganese is many times and sodium 

 always, found present in the ash of plants. 



Sodium is very much cheaper than potassium, and there has been much 

 •discussion as to the use of sodium instead of potassium compounds for plants. 

 ScKlium cannot be used instead of, or to replace, any of that potash which is 

 required for the normal development of the plant. 



Of all the foregoing elements of plant-food, only three or four are included 

 when the subject of fertilizers is considered. These are nitrogen, phosphoric acid, 

 potash, and sometimes lime (calcium oxide.) The remaining plant-food elements 

 are usually present iu such abundance that they are not even discussed. 



Poor Crops. — When a farmer writes that his soil is unproductive and that 

 he harvested only one-quarter of a crop, and wants to know wherein the trouble 

 lies, a very difficult problem is presented. The poor yield may be due to a lack 

 of available nitrogen, phosphoric acid, potash or lime, or it may be due to the 

 poor character, or low ebb, of one or more of the many other essential conditions 

 which surround and influence the growth of the crop. 



Questioning the Soil. — The farmer may question the chemist, or he may ques- 



