104 CAM SPELL'S son, QULTUBE M \\ir.vL 



ments on a tract of land in Iowa "which with stable manure 

 every time produces a smaller crop than without." No 

 explanation. 



WHAT THE SOIL IS. 



Now the soil is, in fact, a part of the volcanic matter 

 which composes most of the earth. It is broken into 

 minute fragments. These fragments are perfect speci- 

 mens of rocks and stones or pulverized minerals. But 

 they are so fine that the different minerals readily combine 

 by chemical action. The plant food is organic in nature. 

 It is composed of different mineral substances united by 

 chemical action or otherwise. We do not know and we 

 never can know just how and why these combinations 

 are effected. 



We do know that nitrogen plays a large part in form- 

 ing these organic substances which are the food of the 

 plants. We know that nitrogen abounds in the air and 

 that it may easily be separated from the other component 

 parts of the air. We know that this chemical 'action is 

 possible only where there is water, and we know that it is 

 promoted by the rays of light from the sun. We feel sure 

 also, that in some way the electricity ever present in the 

 earth and in the air plays a part in this laboratory in 

 developing growth. 



What we can do by cultivation of the soil is to bring 

 about the conditions best suited to whatever action is 

 necessary to develop plant food in the soil. The ideal soil 

 condition is one where there is just the right amount of 

 water and air and other elements. We can do a great 

 deal in assisting nature, or at least in not obstructing 

 nature, in this laboratory work. And this is scientific 

 soil culture. 



The scientific investigator does not go far in making 



