46 AGRICULTURE FOR COMMON SCHOOLS 



than the dry layer and so is not evaporated. It must be 

 understood, however, that not every bit of moisture can be 

 saved. Some of it finds its way through the dry layer and is 

 lost. A dry layer two and one-half or three inches deep is 

 best for saving the moisture. It is better not to stir the 

 ground deeper than this, for by so doing the roots of the plant 

 are likely to be disturbed. 



When corn plants are eighteen inches high their roots 

 reach clear across the middle between the rows, and some of 

 the roots are not far from the surface. If one of these roots 

 is cut off the plant has to do without the food and water 

 which that root would have furnished. When we stir the 

 ground two or three inches deep we are giving shallow culti- 

 vation. Deeper than three inches is generally called deep 

 cultivation. It is better to have the surface left nearly level 

 after cultivating than to have high ridges. If the cultivator 

 has small teeth or shovels the ridges will not be very high. 

 The high ridges give more surface for the evaporation of 

 water, hence they are not desirable. It is not necessary for 

 the ground between and around the plants to be ridged up 

 to make the plants stand up well. 



The number of times that a crop should be cultivated can- 

 not be told exactly. It should be cultivated often enough to 

 keep down the weeds and to keep the surface loose. Even if 

 the weeds are all killed the ground should be stirred about 

 once a week until the crop is well grown, for the loose surface 

 will become more or less settled and more water will be 

 evaporated. In other words, the soil mulch will wear out and 

 must be renewed. 



There are many kinds of cultivators, but to be effective 

 they must all have two merits. They must be easily regulated 



