106 CAMPBELL'S SOIL CULTURE MANUAL 



and to this end we have spent nearly a quarter of a century 

 in soil culture experiments, study and general observ- 

 ation. 



In 1891 we became positive of our ability by observing 

 certain physical conditions of the soil to secure good crops 

 during drouthy condition, while others failed; a little 

 later we were convinced by repeated results that the aver- 

 age yield of the great semi-arid section even in good sea- 

 sons could easily be doubled, and now it is evident there 

 can be even a greater increase in the yields and to the devel- 

 opment of increased available fertility by utilizing more 

 of nature's abundant resources, such as heat, air, water 

 and light through chemical action which we have found 

 is great or small, just in proportion to the ability of the 

 soil to combine these elements in proper quantities under 

 such ideal conditions as shall cause the most complete 

 chemical action for the production or development of the 

 necessary amount of fertility, and that this all important 

 ideal condition of the soil can be established by scientific 

 soil culture. 



