Ridged or Flat Cultivation 165 



of the later season are largely retained very close to the surface, 

 so that stirring the surface may hasten the evaporation of it, and 

 at the same time prevent a. part of it from being conducted 

 downward into the soil by capillarity. 



Further than this, in the latter part of the season many plants 

 in humid climates put out new roots, which reach up extremely 

 close to the surface, in order to take advantage of the showers 

 whose waters are retained there; and tillage at once after a 

 rain may do positive injury to the crop, by destroying these roots 

 before they have conveyed the soil moisture to the plant, heavily 

 laden with plant-food, as it is likely to be under these conditions. 



9. Proper Depth of Surface Tillage and Ridged or 

 Flat Cultivation 



It will be readily inferred, from what has already been 

 said, that the best depth of tillage will vary with the season. 

 Early in the season it should almost invariably be deep, not less 

 than 2 to 3 inches, but rarely should it be deeper than this. The 

 deep stirring in the spring is to develop fertility by thoroughly 

 aerating the soil and making it warm, so that the nitrates are 

 rapidly formed. Later in the season the cultivation should be- 

 come more and more shallow, until, as already pointed out, it 

 should be finally abandoned altogether. 



When it is stated that the early tillage should have a depth of 

 2 to 3 inches, this should be understood as meaning that the 

 whole surface of ground not occupied by the plants should be 

 stirred to this depth, and some tool which actually displaces the 

 whole of the soil to a uniform depth does the best work. As a 

 rule, the field should not be furrowed with deep grooves and 

 ridges, for this method early dries out too large a volume of the 

 soil, and thus lessens its productive power. Indeed, it should 

 always be kept in mind that the surface soil in humid climates is 

 the most valuable soil of the field ; and for this reason, after the 

 period of stirring for fertility is passed, as little should be moved 

 and allowed to become dry as will answer the needs of the mulch, 

 because in this condition the soil is valueless in plant feeding. 



