114 



LAND DRAINAGE AND IRRIGATION 



rated with water to within three feet or even eighteen inches of the 

 surface. Most farm crops, however, do best when such lands are 

 thoroughly drained. 



Use of Spade May be All That is Necessary. Frequently 

 water standing in a cropped field may be gotten rid of by spading 

 a shallow trench to some drain or roadside ditch. Sometimes 

 the placing of a galvanized steel culvert under a road-bed, or the 

 mere lowering of such a culvert, is all that is necessary to enable 

 the water to escape, or to prevent its backing up on the land. 



FIG. 48. A well-sodded surface-run. The grass prevents soil washing. (Wisconsin Station.) 



Plow Furrows as Drains. On tight soils, and where fields have 

 little slope, water from rainfall causes much injury because of 

 insufficient natural surface drainage. The plowing of these fields 

 in narrow strips of about four rods wide up and down the gentle 

 slopes often provides good surface drainage. When this method 

 is practiced, the "back furrows" should form slight elevations 

 running lengthwise through the middle of each plowed strip, and 

 the "dead furrows" should be kept open. In this manner the 

 water from rains or melting snow drains from the back furrows to 

 the dead furrows, thence down the dead furrows and off the 

 field (Fig. 47). 



Surface-run a Necessary Drain. A surface-run is a shallow 

 low runway for water about one and one-half feet deep and ten 



