HARROWING, CULTIVATING 167 



lost in increased draft, deep cultivation is wasteful 

 of soil water, because it Brings to the surface a 

 large amount of moist soil which soon becomes 

 dry. The moisture in this soil might better have 

 been left below where it could have been used by 

 plants. Moreover, a deep-working cultivator 

 leaves the soil in ridges, thus exposing more sur- 

 face for evaporation; for some water is lost from 

 the soil even when it is covered with the very best 

 mulch. Furthermore, the valleys made by deep 

 cultivation are the beginning of erosion. 



Deep cultivation may cut many of the feeding 

 roots of the crop. The roots of plants naturally 

 seek the richest part of the soil. The soil near 

 the surface usually contains the most plant food, 

 because so much soluble plant food has been left 

 there by the evaporation of soil water, and be- 

 cause the surface soil contains more humus, more 

 germ life, more air and more of everything that 

 makes for fertility. 



In all ordinary soils the largest proportion of 

 feeding roots is found immediately below the range 

 of cultivator teeth, provided that part of the soil 

 is in good texture. In a warm climate plants root 

 deeper than in a cool climate. Deep cultivation 

 during the growing season cuts off innumerable 

 rootlets and root hairs that are foraging in the 

 richest places they can find. To "plow out" a 

 corn field four or five inches deep, in July, is to 

 practise root pruning of a severe character. Some 

 farm crops do not seem to be injured appreciably 

 by this kind of root pruning, but none are benefited 

 by it, and some are injured. Deep tillage may 

 be given the crop early in the season, if necessary, 

 but shallow tillage after it begins to shoot. When- 

 ever the soil becomes hard, as after a beating rain, 



