1 12 to 15 inches deep. Six of the holes were 



made in a circle having a r.ulius of appro i 

 I ei The remaining 12 holes were distributed in a circle 

 having a radius oi i 1 \ feet, sufficient to include most of 

 the root system of the treated tree. After the fertilizers 

 had been applied, no attempt was made to till hi hoi 

 and no supplemental watering was done 



Injection of Liquid Fertilizers 



The five kinds of fertilizers applied in holes were ap- 

 plied also by the soil injection method. Solutions of the 

 five fertilizers were injected 18 to 24 inches deep with a 

 soil needle (Fig. 5 -nd 6) and a hydraulic sprayer at 150 

 pounds pressure. The volume of fertilizer used at each 

 injection point was carefully regula ed by opening the soil 

 needle valve for a predetermined number of seconds. Fif- 

 teen gallons of a fertilizer solution were used per tree. The 

 15 gallons of liquid fertilizer were evenly divided among 

 14 injection points about each tree. Four injections were 

 made on four sides approximately 2' 2 feet from the ttee 

 trunk, and the remaining 10 injections were made in a 



FIG. 5. — Hydraulic injection of liquid fertilizer at 150 pounds 

 pressure through a soil needle. 



b 



' 





1 "■ ' I i merit ol links .noun. I 



an experimental trei fertilized by thi method 



h-bat (left) and soil needle designed and used 

 in the authors of tins publication The punch-bar is ma 

 .1 hardened steel axle on which arc fool rest and a 



Tin soil needle is hW- types available commercially. 



