TILLAGE. 81 



The longer weeds are allowed to grow the greater the 

 loss of food and water which the crop might otherwise 

 have made use of. 



Aaother chief purpose of crop cultivation is to keep 

 the surface of the soil loose and porous. Some soils 

 "bake" or "cake'^ on the surface, especially if they 

 have been stirred while wet. Shallow cultivation is 

 all that is needed in such cases. If the soil has been 

 deeply plowed or is naturally loose, it will hardly be- 

 come too compact while the crop is growing. The 

 roots of such plants as corn often grow more rapidly 

 than do the stalks while the plant is young. Close, 

 deep culture necessarily injures or destroys many 

 roots. Root pruning is almost always injurious to 

 the crop. It may be a necessary evil, but no more of 

 it should be done than is necessary. Deep culture 

 should be given, if at all, while the plants are small. 



The relation of cultivation to ^oil moisture and its 

 evaporation is important. Improving the capillary 

 power of the soil may be accomplished by tillage in 

 many cases, by compacting too open soil, and loosen- 

 ing too compact soils. This work, except at the sur- 

 face, should be done before the crop is planted. At- 

 tempts to improve the physical condition of the soil to 

 the depth of six inches after the crop has well started 

 its growth will usually do more harm than good. 

 Stirring the surface soil during drouth causes some' 

 loss of moisture by increase of evaporation. If it is 

 desired to have a pan of wet sand dry rapidly, it is 

 , well to stir it. But the loosening of the surface soil 

 and its becoming quite dry saves the moisture in the 

 soil by the dried surface acting as a mulch and thus 

 checking evaporation. A thin coating of finely di- 



