Table S. — Color ratings (1 to 5)f of three deciduous hardwoods during a 2-year period of fertilization treatments at Lisle, Illinois. 

 Each color rating for treated trees represents the average for five contiguous trees in a plot. 



f Color rating: l, yellow green; 2, light green ; 3, green; 4. moderately dark green; 5 dark green. 



TABLE 9. — Color ratings (1 to 5)f of three deciduous hardwoods during a 2-year period of fertilization treatments at Lisle, Illinois. 

 Each color rating tor treated trees represents the average for five contiguous trees in a plot. 



t Color rating: 1. yellow green; 2, light green; 3, green; 4, moderately dark green; 5 dark 



growth that, measured by circumference increase, was con- 

 siderably greater than growth of the controls: 52 r r greater 

 in the pin oak, 39% greater in the white ash, and 739r 

 greater in the honey locust. 



The color data for the fertilizer treatments of the three 

 tree species in the 1963 and 1964 tests are shown in Table 

 7. These data were analyzed statistically. The color re- 

 sponse to the various methods of treatment is presented 

 in Table 8. Nitrogen fertilizers applied to the soil surface, 

 in holes made in the soil, or as solutions injected into the 

 soil, produced a foliage color that was significantly darker 

 than foliage color of the trees receiving no treatment. Dur- 

 ing the 2-year test, the solution injection and surface 

 broadcast methods appeared slightly better than the soil- 

 hole method. 



The foliage color of the trees receiving foliar fertiliza- 

 tion was not significantly better than the foliage color 

 of the untreated trees. In the first year of the experiment, 

 no difference in color of foliage could be detected between 

 the trees receiving foliar treatments and the untreated trees. 

 In the second year, the foliage of all three tree species 

 receiving foliar fertilization appeared slightly darker in 

 color than foliage of the untreated controls. However, the 

 response to foliar fertilization was not nearly as marked 

 as the response obtained from any one of the three soil 

 fertilization methods. 



A comparison of the color responses to the various 

 fertilizers tested is presented in Table 9. Only those trees 

 receiving fertilizer treatments containing nitrogen had 

 leaves that were significantly darker green in color than 

 leaves of the untreated controls. There was little or no 



color response to phosphorus and potassium applied to 

 the soil. The addition of phosphorus and potassium to 

 nitrogen sources did not produce a color response that was 

 greater than that produced by nitrogen alone. The addition 

 of minor elements to NPK produced no measurable color 

 response. Ammonium nitrate as a source of nitrogen ap- 

 peared to give a darker green color to leaves of oak and 

 ash than did urea; on locust, urea appeared more effective 

 than ammonium nitrate in producing the darker color. 



TOXICITY OF FERTILIZERS TO BLUEGRASS 



Because some of our experiments showed that surface 

 applications of nitrogen fertilizers constituted a practical 

 and economical method for fertilizing established shade 

 trees, we conducted additional experiments to determine the 

 rates at which these applications could be made without 

 injuring the grass that is commonly found under and 

 around such trees. 



Wyman ( 1936) reported a 2-year test on the applica- 

 tion of ammonium sulfate ( 20-0-0 ) to a lawn at rates 

 as high as 20 pounds of N per 1,000 square feet. He 

 found that on dormant Kentucky bluegrass, when precipi- 

 tation was ample, no injury resulted from ammonium sul- 

 fate applied at rates of 10 pounds of N per 1.000 square 

 feet and no serious injury at rates as high as 16 pounds 

 After the grass had started to grow, 4 pounds of N per 

 1,000 square feet were applied without injury to grass; 

 K) pounds per 1,000 square feet caused considerable burn- 

 ing but left some grass green. 



In tests at the Morton Arboretum, we observed no 

 injury to the Kentucky bluegrass. Poa pratensil I... growing 



