DAIRY AND SEED IMPROVEMENT MEETINGS. 29 1 



will be over-ripe and shatter very badly. These pure lines, 

 which it will be remembered are each the descendants of a 

 single plant, ripen very evenly. We believe that they will prove 

 to have many other valuable characters. 



Wq are continuing each year to select plants from various 

 commercial varieties,. Some of these new pure lines, selected 

 in 1911 and 1912, are now ready to go into field tests. Of these 

 we shall perhaps have something to say at some future time. 



THE RELATION OF MANURE TO SOIL FERTILITY. 

 Earl Jones^ Instructor in Agronomy, University of Maine. 



The rock from which the soil was formed is the original 

 source of the phosphoric acid and potash found in our soils. 

 These elements of plant food were not available when in that 

 form and rock ground to a powder would not be used for a 

 fertilizer, as the plant food is unavailable. During the long 

 period of time in which our soil has been formed from the solid 

 rock, these materials have been slowly made available. By this 

 we mean that they have been changed into a condition in which 

 they will dissolve in the soil water, so that the plant can take 

 and use them. 



We will briefly consider the factors that make the plant food 

 in the soil available. The soil water, especially water con- 

 taining carbon dioxide, is a very important factor. This carbon 

 dioxide is produced by the decay of organic matter in the soil 

 and is washed down in the rainfall. Acids formed by decaying 

 organic matter and soil bacteria are also important factors. 

 Plant food is made available slowly and of the total supply in 

 the soil only a small portion becomes available each year. If it 

 all became soluble and available at one time, it would be leached 

 out in the drainage waters, because the plants could not use it 

 in such large amounts ; 'hence, this provision that plant food 

 become available slowly is Nature's method of giving perma- 

 nence to our soils. 



Nitrogen, probably the most important plant food element 

 from our standpoint, was not found in the rocks from which 



