100:13:65. On this basis, the relative amounts 

 of N and P in the central treatment used here 

 were satisfactory while the amount of K 

 should have been 3 to 4 times greater. The 

 response surface analysis of the study data, 

 by indicating that the K supply was low, 



agrees with these general relationships. Thus, 

 further testing is needed to determine the 

 optimum levels of supply; and the results re- 

 ported here should be considered as a first 

 approximation only. 



References 



1. Bjorkbom, John C. 



1972. Response of paper birch seedlings to 

 nitrogen, phosphorus, and potassium. usda 

 Forest Serv. Res. Note NE-157. 4 pp. NE Forest 

 Exp. Sta., Upper Darby, Pa. 



2. Chapmain, Homer D., and Parker F. Pratt. 

 1961. Methods of analysis for soils, plants 

 AND waters. Univ. Calif. Div. Agr. Sci. 169-170. 



3. Clutter, Jerome L. 



1968. Design and analysis of forest fertiliza- 

 tion experiments. In Forest fertilization, 

 theory and practice. Tenn. Valley Auth., Nat. 

 Fert. Develop. Cent. Muscle Shoals, Alabama. 



4. Cochran, William G., and Gertrude M. Cox. 



1957. Experimental designs. Second Edition. 

 661 p. John Wiley and Sons, Inc. 



5. Ingestad, Torsten. 



1971. A definition of optimum nutrient re- 

 quirements in birch seedlings. II. Physiol. 

 Plant. 24: 118-125, illus. 



6. Mader, D. L., and M. C. Hoyle. 



1964. An inexpensive portable unit for per- 

 chloric ACID digestions AND SEMIMICRO-KJEL- 

 dahl DETERMINATIONS. Soil Sci. 98: 295-299, 

 illus. 



7. Perkin-Elmer Corp. 



1968. Analytical methods for atomic absorp- 

 tion SPECTROPHOTOMETRY. Perkin-Elmer Corp., 

 Norwalk, Conn. 



—JOHN C. BJORKBOM 



Research Forester 

 Northeastern Forest Experiment Station, 

 Forest Service, U. S. Department of Agriculture 



Warren, Pa. 



Manuscript received for publication 7 August 1972. 



4 



U. S. GOVERNMENT PRINTING OFFICE: 1973-710-081/144 



