8 



A summary of the results from four different methods 

 of applying nitrogen-containing fertilizers to the experi- 

 mental shade trees is given in Table 5. These data were 

 obtained by averaging data from the nitrogen-containing 

 treatments listed in Table 4. Data from treatments 15 and 

 16, in which only P and K were used, are not included in 



Table 5. — Average increases in growth of three deciduous 

 hardwoods during a 2-year period of nitrogen fertilization treat- 

 ments at Lisle, Illinois, 1963 and 1964. 



TABLE 6. — Average increases in growth of three deciduous 

 hardwoods during a 2-year period of soil fertilization treatments 

 at Lisle, Illinois, 1963 and 1964. (Trees given foliar applications 

 are not included. ) 



Table 5. The amount of N applied per tree was the same 

 for each method of application except the foliar spray. 



Trees given the foliar spray did not make substantially 

 greater growth than the unfertilized trees ( Table 5 ) . 

 Growth differences between these two groups of trees were 

 no greater than would be expected from normal biological 

 variation. 



The three methods of soil application appeared to be 

 about equally effective on pin oak. On white ash, the 

 solution injection method produced a noticeably greater 

 response than the hole method of soil application. On 

 honey locust, the surface application produced the greatest 

 response. Of the three methods of soil application, surface 

 application produced the greatest amount of total growth 

 on trees of the three species combined. The precipitation 

 that occurred from April through September in both 1963 

 and 1964 (Table 3) was adequate to carry the surface- 

 applied fertilizer into the soil. 



The response of the experimental shade trees to five 

 fertilizers applied to the soil is summarized in Table 6. 

 The data were obtained by averaging data from the soil 

 treatments included in Table 4. Growth of only those 

 trees receiving nitrogen treatments was significantly better 

 than growth of the untreated trees. The application of 

 phosphorus and potassium to the soil did not bring about 

 a significant growth response; nor did a combination of 

 phosphorus, potassium, and nitrogen produce a response 

 that was significantly greater than that produced by nitro- 

 gen alone. The addition of minor elements to NPK pro- 

 duced no significant growth response. Ammonium nitrate 

 and urea appeared to be about equally effective as nitrogen 

 sources. The addition of nitrogen to the soil resulted in 



• Significant at tl 



•• Significant at thi I level 



