"Another idea that I pondered over a great deal was tlie state- 

 ment that tillage makes a soil more fertile. Experience had taught 

 me that the better I prepared my corn ground and the more I culti- 

 vated, the better the crop ; but I had supposed that this was merely 

 because the soil was made more mellow and the roots liad a chance 

 to spread out further in the soiL Little by little I have come to 

 understand that good tillage helps to incike digestible^ or available, 

 some of the tough lylant-food tohich lies hi the soil. 



" When you pnblislied your first three lessons on the soil and its 

 fertility, I wish you had directed the printer to put in large letters 

 the idea that the soil is a laboratory which must be kept i?i good 

 repair, so that ' chemical activities,' as you say, can go on rapidly 

 and unlock the locked-up fertility. You ought to liave made more 

 clear that it is my business to keep the laboratory in repair so that 

 the ' chemical activities ' can go on without hindrance. If you 

 were to ask my idea of a worn-out soil, I should say that it is a case 

 in which the farmer has let the soil laboratory go to ruin. If this 

 is true, then the problem of restoring fertility is. How can I best 

 put the laboratory in repair ? 



" They tell me that soil is made of vegetable matter and rock 

 ground into very fine particles, what I should call stone flour. 

 Please let me say vegetable matter instead of organic matter, for 

 that is the way I am in the habit of thinking. Yes, thank you for 

 suggesting humus ; I suppose it means much the same thing. They 

 also tell me that by much cropping this vegetable matter will grad- 

 ually pass out. It came to me that this may become exhausted, 

 leaving only the stone flour behind. Stone flour is next thing to 

 clear sand and clear sand is next thing to a granite boulder. I can- 

 not conceive much ' chemical activity ' going on in a boulder. 



"If I am right in this, then the first step for tne to take towards 



p7'07noting chemical activities is to imitate nature and add more 



hiunus to the soil by plowing under green crops. I have been 



experimenting along this line for several seasons and in the main I 



think this is the first principle in trying to improve worn-out soils. 



I say ' in the main,' for usually one cannot carry a point by one 



idea. It seems to me that this often causes the failure of many 



well-meaning men who would be progressive ; they go on just one 



573 



