36 



ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 51 



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FILL 



STRAW 



GRAVEL 



Fig- 37. — Coarse jjra'^'pl spread over the original soil surface before ad- 

 ditional soil is applied as a fill will give adequate aeration to prevent root 

 injury. 



Another method of providing adequate aeration and drain- 

 age when the grade level is raised is shown in Fig. 38. With this 

 system, air and water can reach the roots through the tile even 

 when fills are quite deep. Also it is easy to fertilize and water a 

 tree as needed through the radiating tile. First arrange five or 

 more lines of 4- to 6-inch porous drainage tile as spokes of a 

 wheel with the trunk as the hub. Next, arrange a circle of tile 

 as the rim of the wheel, or connect the spokes with straight lines 

 of tile. Make the ends of the tile lines near the tree trunk higher 

 than the ends that join the circle or rim of tile. The outer ends 

 of the radial tile lines may stop where they join the circle of tile, 

 or they may be extended beyond the circle, and they should slope 

 downward for good drainage as illustrated in Fig. 38. Place 

 6-inch bell tiles upright over the junctions of the lines of radial 

 tile and the circle to serve as vents. Extend these upright tiles, 

 held in place by stones, to the planned grade level. 



The opening or well around the trunk can be made of stone 

 or brick and must be as high as the level of fill. Build the well 

 large enough to allow for a 1- or 2-foot open area between the 

 trunk and the well wall. Cover all ground tile to a depth of 12-18 

 inches with rock, then cover the rock with gravel. Place a thin 

 layer of straw or hay over the rock and gravel, then complete 

 the fill with about 12 inches of good topsoil, leaving the well 

 around the trunk, and the bell tiles open. Cover the ends of the 

 lines of tile opening into the well with coarse gravel. A vertical 

 section of the completed fill is shown in Fig. 39. 



In some instances it may be desirable to fill the bell tiles 

 with coarse gravel and cover them with a screen. Also, the entire 

 well can be filled with coarse gravel or with a mixture of equal 

 parts of crushed charcoal and sand. However, if the well is to be 

 filled, it is not necesary to build the stone or brick wall. 



