40 GENERAL CONSIDERATIONS 



of short periods of tillage with cover crops is the best 

 possible form of management for most agricultural 

 soils. 



Improvement of the Soil 



Some soils are in their natural condition exceed- 

 ingly well fitted for the production of crops. . Others 

 require to be altered and improved in one or more 

 directions before they can be made to yield profit- 

 able returns. 



Drainage. — Some of the richest soils are low and 

 flat, and in their natural condition crops are injured 

 by too much water. A water-logged soil can never 

 be productive. In such cases improvement by drain- 

 age becomes a first necessity. Drains are of two 

 kinds, open ditches or surface drains and underdrains. 

 The amount of ditching required to properly drain a 

 piece of wet land will depend on many things. If 

 the land is low and is flooded by water running down 

 from above, a single ditch dug along the upper side to 

 divert the surface water may be all that is necessary. 

 If, however, the land is inclined to be boggy from 

 water that rises up from below through the subsoil, 

 deep ditches at comparatively frequent intervals will 

 be required. Ditches should always be carefully 

 laid out with a level so as to give them a gradual but 

 uniform fall in order that they may carry off the 

 water promptly. In laying out a system of ditches 

 it is necessary to give careful consideration to 

 the matter of securing a free outlet for the water. 

 In very flat level countries it is sometimes necessary 

 to dig large canals for a considerable distance in 



