30 



ILLINOIS NATURAL HISTORY SURVEY CIRCULAR 46 



by tree roots soon leaches away. After the need for annual ap- 

 plications of phosphorus and potassium has passed, annual ap- 

 plications of nitrogen may be needed to maintain vigorous tree 

 growi;h. 



Dry Feeding. — When being applied to a very small tree (less 

 than about one-half inch in diameter near the base), tree food in 

 dry form may be scattered on top of the soil around the tree and 

 worked in with a hoe or soaked in with water. 



Dry feed for a larger tree is commonly placed in holes IV2 

 to 2 inches in diameter and 18 to 24 inches deep. Make the holes 

 with a punch-bar or soil auger, spacing them 24 to 30 inches 

 apart in concentric circles around the trunk (Fig. 30). The 

 outermost circle should be somewhat beyond the limit of branch 

 spread and the inner circles should be spaced to maintain the 

 required distance between the holes. Holes may be within 3 to 5 





Fig. .30. — Dry tree food may be supplied to a tree through holes in the 

 soil arranged in concentric circles around the trunk. These holes, IY2 to 2 

 inches in diameter, 18 to 24 inches deep, should be 24 to 30 inches apart. 



