104 Peach-Growing 



conception that the chemical activities necessary to fertility 

 could not proceed except when the soil was well filled with 

 humus or decaying vegetable matter was reflected in many 

 ways in the improvement of agricultural conditions generally. 

 The organic chemist has made it clear that the by-products of 

 the growth of roots in the soil, in some cases at least, become 

 poisonous or toxic to the plants themselves after a time, and 

 the bacteriologist has developed the thesis that a fertile 

 soil, in addition to being a laboratory where essential and 

 intricate chemical activities are constantly going on, is also 

 a medium in which bacterial life is active almost beyond 

 man's comprehension. This, then, is the present idea of 

 soil fertility — a combination of moisture (as affected by 

 the physical condition of the soil), humus supply, chemical 

 activities, bacterial and other biological activities, organic 

 compounds (which may act adversely), and the presence of 

 the essential plant-food elements. 



It is obvious at once that there must be an interminable 

 correlation between these various factors, and that they may 

 react differently under varying conditions. 



The real problem in tillage is so to control or manage the 

 soil as to bring about such activity of all the biological and 

 chemical forces that are related to soil fertility as will result 

 at all times in their complete correlation in terms of the 

 plant-food requirements of the trees. It is obvious that the 

 problem is much involved and the means of control are 

 often obscure, but experience has taught much with regard 

 to practical methods of tillage. 



With particular reference to peach orchards, there is 

 comparatively little difference of opinion among experienced 

 growers in regard to tillage. While an occasional instance 

 of a peach orchard which has been successful for a long time 



