70 THE PRINCIPLES OF AGRICULTURE 



or spring- tooth harrow, — and its object is pulver- 

 ization of the ground. The finishing is done 

 with a small-toothed and lighter harrow ; and 

 this finishing provides the jeed-bed and the soil- 

 mulch. 



100. The earth-mulch is destroyed by rains : 

 the ground becomes baked. But even in dry 

 times it becomes compact, and capillarity is 

 restored between the under- soil and the air. 

 Therefore, the mulch must be maintained or re- 

 paired. That is, the harrow or cultivator must 

 be used as often as the ground becomes hard, 

 particularly after every rain. In dry times, this 

 surface tillage should usually be repeated every 

 ten days, — oftener or less often as the judgment 

 of the farmer may dictate. The drier the time 

 and the country, the greater the necessity for 

 maintainmg the soil-mulch ; but the mulch is of 

 comparatively little effect in a dry time if the 

 soil moisture was allowed to evaporate earlier 

 in the season. 



101. Surface tillage is usually looked upon 

 only as a means of killing weeds, but we now see 

 that we should till for tillage's sake, — to make 

 the land more productive. If tillage is frequent 

 and thorough — if the soil -mulch is maintained — 

 weeds cannot obtain a start ; and this is the 

 ideal and profitable condition, to which, however, 

 there may be exceptions. 



