beneath the oak, ash, or locust trees treated by surface 

 application with urea or ammonium nitrate at the rate of 

 6 pounds of N per 1,000 square feet. Also, we observed 

 no injury to grass when the fertilizer was applied dry in 

 holes or injected into the soil in solution. Since such 

 variables as time of application, rate of application, and 

 the presence or absence of moisture droplets on the grass 

 blades were not investigated in the Morton Arboretum 

 tests, we included these variables in a series of fertilizer 

 toxicity tests on a lawn near Urbana, Illinois, in the spring 

 and summer of 1964. 



The lawn of a farm residence 1 mile south of Urbana 

 was used in this study. The lawn was predominantly Ken- 

 tucky bluegrass. It had no hisrory of previous fertiliza- 

 tion. The grass was regularly cut throughout the test to 

 a height of approximately 3 inches. Rain provided the 

 only source of water except in one of the tests in which 

 the grass was sprinkled to simulate a heavy dew. A lawn 

 fertilizer spreader, 20 inches wide and typical of the push 

 type commonly used by homeowners ( Fig. 8 ) , was cali- 

 brated to spread 3 pounds of N per 1,000 square feet of 

 soil surface for each of the five fertilizers used in this test. 

 The five fertilizers applied were ureaform, urea, 10-10-10, 

 ammonium nitrate, and ammonium sulfate. 



Each fertilizer was applied at rates of 3, 6, 9, and 12 

 pounds of N per 1,000 square feet on April 15, May 15, 

 and July 30 in bands 20 inches wide and 20 feet long. 

 The 6-pound rate required two applications at the 3- 

 pound rate; the 9-pound rate required three applications; 

 and the 12-pound rate required four applications. An 

 additional test was made on May 15 and July 30 to com- 

 pare the effect of applying fertilizers to wet grass. For 

 this test, a strip of lawn 10 feet long was sprinkled with 

 water immediately prior to applying the 20-inch-wide 

 band of fertilizer. 



FIG. 8. — Surface application of dry fertilizer. A common lawn 

 fertilizer spreader may be used in applying fertilizer to either 

 grass or trees. 



Observations were made 4 and 7 days after each appli- 

 cation, and the phytotoxicity of each application was rated 

 on a scale of through 7 (Table 10). No injuty was 

 recorded for the April 15 applications. Some injury re- 

 sulted from several of the May 15 and July 30 applications. 

 Ureaform caused no observable injury at any time, or in 

 any amount used, on either dry or wet grass. Urea used 



TABLE 10. — Phytotoxicity ratings (1 to 7 ) t of five fertilizers applied to Kentucky bluegrass at Urbana, Illinois. 1904. 



t Phytotoxlcli -in Injurs to ECentuckj bluegrass 0, none: I. vers sliKlii; 



i. moderate; ."'. moderi evere ; '-. severe; .. very severe. 



I, sliatit : :f. sliehi to moderate; 



