Winter Meeting;. 153 



For a soil to be enriched within itself there must be a chemical 

 change. Certain ingredients that have hitherto been insoluble and 

 tmavailable as plant food are rendered soluble and available, and for 

 this chemical change to take place conditions must be favorable. An 

 important factor is the physical condition of the soil. It should be 

 such that it will receive moisture without puddling or baking. It 

 should retain this moisture without remaining wet too long on its 

 .surface, supplying top soil as needed. It should be sufficiently porous 

 to allow the circulation of air. With these conditions present, the 

 micro-organisms, so essential to the food supply of plants can receive 

 the air, temperature and moisture necessary for their existence. Chemi- 

 cal changes will take place in the organic and inorganic, rendering in- 

 soluble substances available as plant food. 



The physical conditions of the soil can be regulated to a certain 

 extent, at least, by the scientific use of cover crops. 



The chemical study of the soil, even the chemistry of the re- 

 lation of cover crops to the soil, is too deep, and requires too much 

 time for the ordinary farmer to fathom its depths, but if he will 

 acquire the fundamental principles, and will read and keep pace with 

 what is being done by those who give it their entire time, experi- 

 menting a little on his own account, I assure you that he will not be 

 growing the same crop year after year on the same soil, returning 

 nothing and reaping a smaller return each year. He should study the 

 signs of soil debility. If the foliage is generally pale and anaemic 

 when there is a proper supply of moisture, he should know that it 

 is the lack of nitrogen, and that leguminous crops grown on this soil 

 will improve it. It is not necessary that he should know all about 

 the particular family of microbe that lives on the roots of these 

 legumes, making the gathering of this nitrogen from the air possible, 

 or how it is deposited there and held as available plant food. 



Aside from the nitrogen gathering power of the legum.es, cover 

 crops may be said to enrich the soil. While they really add nothing 

 chemically speaking, yet they bring about a transformation of min- 

 eral substances hitherto unavailable and leave this with the soil for 

 the nutrition of other plants. This transformation is brought about 

 by the combined chemical and physiological action of the roots of all 

 plants. At the tip of each root there is through the physiological ac- 

 tion of the plant an exudation of chemical substances that act on the 

 insoluble mineral matter rendering it available as food which the 

 same root may take up and store in the same plant. If this plant is 

 placed under or even remains on the soil, the latter is enriched to 

 the extent of such chemical change. 



