34 BULLETIN 355, U. S. DEPARTMENT OF AGEICULTUEE. 



Surface drainage (Ref. No. 8, pp. 7-9). — In the removal of surface 

 water it is ordinarily necessary to use open ditches of sufficient size 

 to carry the water coming to the dramed land from adjacent terri- 

 tory. The size of the ditch necessary in such a case can be approxi- 

 mately estimated by observing the flow of water following a severe 

 freshet. Wlien the surface water from large areas is to be carried 

 away it is best to secure the services of an engineer who, after mak- 

 ing the necessary survey of the area to be drained, can compute the 

 size of the ditch necessary. 



In the case of comparatively level land, where it is impossible to 

 establish an outlet for subsurface drainage, surface drainage should 

 be made as effective as possible. This is especially necessary where 

 the land is underlain by an impervious clay subsoil. It is often 

 practical to use the common plow in ditching 'such level areas. The 

 plowing should be done in long narrow lands, and the dead furrows 

 should be carefully cleaned out to serve as drainage ditches. It is 

 frequently necessary to cut ditches across from one dead furrow to 

 another in order to drain a slight depression which would otherwise 

 be fiUed with water. These narrow plow lands should usually be 

 kept in the same position for two or three years in order to round up 

 the back furrow somewhat and deepen the dead furrow, but they 

 can not be kept longer than three years ordinarily without widening 

 the dead furrow to an undesirable extent. After this the plowing 

 must be reversed, and the first two furrows of the lands turned into 

 the dead furrows. This method of surface drainage has its greatest 

 objection, perhaps, in the difficulty which comes from working over 

 the open-furrow ditches. 



The timely use of a shovel or large hoe in the spring will greatly 

 aid in removing the surface water coming from rain and melting snow. ' 



Subsurface or underdrainage (Ref. No. 8, pp. 27-34). — Practically 

 all underdrainage is now accomplished through the use of common 

 porous clay tile or glazed tile, laid loose jointed so that the water 

 may pass into the drains through the joints or where the tile meet. 

 The glazed tile are usually more expensive than the porous, but they 

 are also more durable. Factors of greatest importance to be deter- 

 mined in planning an underdrainage system are (1) depth at which 

 the tile should be placed, (2) the available fall or grade of the tile, 

 (3) the system to be used, (4) the distance apart of tile lines or laterals, 

 and (5) the size of tile to be used. 



Depth. — The depth for placing tile is dependent upon several 

 things. First of all, tUe must always be placed below the depth of 

 tillage and also below the frost line. Freezing will crumble porous 

 tile, and it causes heaving of the ground and displacement of the tile 

 in any case. The depth to which tile should be placed varies also 

 with the type of soil and the desired depth of water table. The 



