70 THE AMERICAN PEACH ORCHARD 



will be given with light tools and applied to the sur- 

 face, the intention being merely to maintain a light 

 dust mulch upon the land. The purpose of this dust 

 mulch is to prevent the evaporation of water. 



It is well understood at the present time that the 

 soil is a great laboratory in which all kinds of chem- 

 ical and even biological processes are going on, all 

 of which processes are infinitely important to the 

 peach tree. These chemical and bacteriological proc- 

 esses cannot take place except when a certain 

 amount of moisture is present, and .especially do they 

 require a constant supply of air. The presence of 

 fresh air enables the bacteria to live and thrive and 

 serve their various beneficent uses in the soil. The 

 air also assists in the necessary chemical changes, 

 and especially in the conversion of nitrogen in the 

 soil into available forms as nitrates. Until the nitro- 

 gen is changed into these available nitrates it can- 

 not be taken up by the trees. The necessity of these 

 changes brought about by action of the air applies 

 to much of the nitrogen which is given in the form 

 of fertilizer. 



Of course, it is still recognized that tillage kills 

 the weeds and that this is an important office. No 

 man wants to have a weedy orchard unless he pur- 

 poses to leave a heavy stand of weeds in the latter 

 part of the summer to take the place of a better- 

 grown cover crop. The handling of the cover crop 

 is discussed elsewhere, but it is to be observed at 

 this point that the cover crop following at this pe- 

 riod has a definite part in the program of orchard 

 work. The scheme of management will, therefore, 

 provide for a heavy plowing in early spring, for sev- 

 eral successive surface cultivations at periods of 5 

 to 10 days apart, and finally for the introduction of 

 a cover crop. The time when this cover crop will 



