FERTILIZERS. 33 



The inorganic elements, which form only about five per cent, of the constituents of 

 plants, are eight or ten in number, but most of these are, as a general rule, supplied in 

 abundance by the soil. 



Prof. Atwater also asserts that we may take it as pretty well settled &quot;that the only ingre 

 dients of plant-food which we need supply to our soils are Potash, Lime, Magnesia, Phosphoric 

 Acid, Sulphuric Acid, and Nitrogen. Iron and chlorine are necessary to the perfect growth 

 of plants, but only in minute quantities. Silica and soda are needed, if at all, in similarly 

 small proportions. Every ordinary soil supplies these last four substances in abundance. 



Of the above list the magnesia is rarely deficient in even &quot;worn-out&quot; soils. Sulphuric 

 acid and lime are more often lacking, and hence, doubtless, one reason of the good effect so 

 often observed from the application of lime and plaster. The remaining substances, Phos 

 phoric Acid, Nitrogen, and Potash, are the most apt to be deficient. In some soils one, in 

 others several or all of these may be wanting. When we say the ingredients are &quot;wanting,&quot; 

 we do not mean that the soil does not contain them, but that it does not supply the crops as 

 much as they need. It is not so much because our &quot; worn-out&quot; soils have not enough plant 

 food in store, that crops starve upon them, but rather, because the food is locked up in such 

 combinations that the roots cannot get at and use them. Such is the general result of the 

 best testimony that experience and experiment have placed at our disposal.&quot; 



We find that the elements usually deficient in almost all soils, as above stated, are Phos 

 phoric Acid, Potash, and Nitrogen. Oxygen, hydrogen, and carbon, those elements supplied 

 by the atmosphere, will be abundant and always available, providing the plants to be culti 

 vated are grown in such a manner that the air can have free access to them. When the 

 roots and stalks are so compact that the air and sunlight cannot penetrate the dense mass and 

 the air circulate freely among them, there will never be a perfect or healthy growth of any 

 crop, though some crops require more favoring in this respect than others. Sufficient space 

 must be given the stalks and roots, and with a good supply of air and sunlight, other cori- 

 ditions being equally favorable, a good crop must of necessity follow. Nitrogen, as we have 

 previously stated, although furnished in part by the atmosphere, is not thus furnished in suffi 

 cient quantity for a perfect plant growth, and must needs be supplied by man in some form. 

 Water is also an essential agent in furnishing a source of food supply to plants, since the 

 elements derived from the soil can be appropriated to the use of the plant only in a liquid, 

 or soluble form, and water is necessary to produce this condition of these elements. Some 

 plants require more water than others, but all require it in a greater or less quantity. It is 

 stated from good authority that the cabbage plant is composed of about nine-tenths water, 

 and the potato-tubers nearly three-fourths, which shows how large a proportion of water 

 enters into the composition of some plants. 



General Propositions Concerning Plant Food. The following important 

 propositions concerning plant food, agriculturally considered, are given by Dr. E. L. Sturte- 

 vant of Massachusetts, an authority that will be a sure guaranty of their reliability and true 

 value to the farmer. 



1st. The soil contains plant-food. 



2d. The plant removes this plant-food from the soil. 



3d. Analyses of plants will show the character and quantity of the plant-food removed 

 from the land. 



4th. A supply of the elements removed by the plants from the soil in such a way that 

 they can be appropriated by the plants, will produce the plant-growth, under proper condi 

 tions. 



5th. Plants remove varying quantities of plant-food from the soil, according to their 

 species, their manner of growth, and the proportions and quantities of plant-food present in 

 the soil. 



