SOIL MANAGEMENT. 35 



The objection to open surface ditches is that they are diffi- 

 cult to keep free from weeds and, further, that they restrict 

 cultural operations and occupy valuable land. However, a 

 great deal of unprofitable land can be reclaimed by this method. 

 Care should be taken that the sides are sloping so that they do 

 not become under-washed and subsequently collapse. 



The most efficient system is tile-draining. Two kinds of 

 tile are in common use — (1) clay tile, well burned, cylindrical 

 and straight, and (2) concrete tile, both being made in about 

 12-inch lengths. These are placed end to end at the bottom of 

 the furrows, the joints being uncemented. The water per- 

 colates through the sides of the tile and through the joints and 

 then down the drain. 



System of Drainage. — Naturally the outlet should be 

 towards the lowest part of the land, and the mains should run 

 along the lines of natural drainage. The laterals are generally 

 single lines serving as collecting drains and usually arranged in 

 parallel systems. Intercepting or cut-off drains are those laid 

 at the base of a slope to collect the water that the heavier sub- 

 soil layers are carrying to the lower level lands. 



Depth and Distance Apart of Drains. — These are 

 matters of extreme importance and are governed by a number 

 of considerations. From the point of view of drainage, the 

 sub-soil is of more importance than the surface soil. In general 

 the finer the texture the shallower the drains and the closer 

 together must the lines be placed. The depth varies from 

 2 feet in heavy soils to 4 feet in more open types. In clay 

 soils the drains are usually placed from 40 feet to 60 feet apart, 

 whereas in open sandy soils they may be placed from 80 to 150 

 feet apart. Naturally, too, in most soils, except heavy clays, 

 the deeper the drains are placed the wider should be the inter- 

 vals between the lines. The size of the tile will vary according 

 to the area to be drained and the grade. The laterals usually 

 consist of 4 to 6 inch tiles, while the sub-mains and mains are 

 composed of tiles 9 and 12 inches in diameter. The grade 

 should be as steep as possible, with a fall not less than six 

 inches in every 100 feet. 



Obstructions may be caused by roots, animals and silting. 

 Usually little difficulty is found in locating these, and if the 

 ends are closed with small meshed wire-netting, small animals 

 will be prevented from entering. It is remarkable how seldom 

 even a deep-rooted crop like lucerne will obstruct a drain. 



