Fei tili/ingaiul Watt-ring Trees 1 1 



oxygen decrease with depth, most active, absorbing roots are 

 near the soil surface. 



The placement of fertilizer for the most efficient uptake of 

 the mineral elements by tree roots cannot be determined 

 with precision because the location of the absorbing roots is 

 usually unknown. Between four and ten major woody roots 

 originate from the root collar of most trees. These grow 

 horizontally through the soil and are most often limited to 

 the topsoil. They decrease in diameter rapidly within a 

 distance of 3 to 1 5 feet from the trunk and form an extensive 

 network of long, ropelike roots 'A to 1 inch in diameter. At 

 the ends of these roots, a network of smaller roots branch 

 to form fans or mats composed of thousands of fine, short, 

 nonwoody tips. These fine roots, with accompanying fungi, 

 are the primary sites for the absorption of water and 

 minerals. 



These fans of fine, absorbing roots are not uniformly 

 distributed around the tree. In a mature tree, a circular area 

 four to seven times the area covered by the branches will 

 encompass these scattered fans. In newly established trees, 

 in specimen trees in open lawns, and in trees in parkways, 

 the distance and direction of root spread can be estimated 

 with reasonable judgments. Determining the root area for 

 a particular mature tree in a grove or wood lot is difficult, 

 if not impossible, and the efficiency of fertilization is greatly 

 reduced. 



For ease in calculation and application, we recommend that 

 fertilizer be applied in square or rectangular areas and that 

 the soil area available, not the size of the tree, be the 

 determining factor in placing the fertilizer. The minimum 

 area should have its four corners positioned so that all the 

 surface area beneath the drip line of the tree is treated 

 (Figure 4). Increasing the size of the treatment area may 

 encourage additional tree growth but with decreasing cost 

 effectiveness. 



