20 ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 51 



to a suitable free outlet or, if such an outlet is not available, a 

 dry well may be installed. A dry well (Fig. 17) is a large hole 

 filled with gravel into which the water can flow. In some locations 

 the drain tiles empty into a storm sewer. Never connect a drain 

 to a sanitary sewer. Do not use crushed limestone in the bottom of 

 the hole; it tends to create an alkaline condition and cause a 

 tree to develop chlorosis. 



Impnjving soil fertility and texture. — Heavy clay soil, low 

 in nutrients, does not allow for adequate aeration and retains 

 too much water for good root growth. Light, sandy soil is low in 

 nutrients, allows for excessive aeration, and does not retain 

 enough moisture for good root growth. 



Poor quality soil can be improved in texture by adding peat 

 moss, granulated sphagnum, well-rotted manure, or other suita- 

 ble materials. Well-rotted manure supplies some nutrients. Usu- 

 ally it is not necessary to add commercial fertilizer until new 

 root grow^th has developed. However, if the soil is low in nutri- 

 ents you can improve it by adding superphosphate or commercial 

 fertilizer high in superphosphate such as a 4-12-4 formulation. 

 Five pounds of 20 percent superphosphate is recommended for 

 each cubic yard of soil (S-^'j. ounces per bushel). The amount of 

 commercial fertilizer to use varies from 3 pounds per cubic yard 

 of soil (2^4, ounces per bushel) for small trees with bare roots to 

 10 pounds per cubic yard of soil (7V2 ounces per bushel) for 

 large trees with balls of soil. 



Breaking the ball. — Delay in planting after a tree is dug may 

 result in the formation of a hard crust an inch or more deep at 

 the surface of the ball of soil, especially if the soil is heavy clay. 

 To assure a better moisture and air supply for good root growth, 

 you can fork off or fracture the hard crust, or punch holes 

 through it, before the backfill is added. A light surface applica- 

 tion of a nonionized detergent (not over 1 ounce in 1 gallon of 

 water) may help in initiating water penetration of the ball of 

 soil that has a hard crust. 



Placing the plant. — Before placing the tree in the hole, put 

 2-3 inches of good loam soil in the bottom, or over any drainage 

 material provided, including tile and gravel. To avoid air pockets 

 under the soil ball, arrange the soil at the bottom of the hole so it 

 is slightly higher in the center. If the tree was marked for proper 

 orientation before it was dug, set it so that each side will have 

 the same exposure or position that it had in its previous location. 



