EXPERIMENTAL FIELD STUDIES 

 ON SHADE TREE FERTILIZATION 



E. B. Himelick, Dan Neely, and Webster R. Crowley, Jr. 



MUCH OF THE PUBLISHED INFORMATION con- 

 cerning response of trees to the addition of nutrient ele- 

 ments comes from the fields of pomology and forestry, 

 very little from arboriculture. In orchards, the response 

 is usually measured in yields of fruit, which may or may 

 not be related to tree growth. The fertilization studies in 

 forestry have been directed toward improving the growth 

 of seedlings in the nursery or of young trees in plantations. 

 The responses may be quite different from those of estab- 

 lished trees in lawn areas. Recent reviews of field studies 

 on nutrient response in forest trees were prepared by 

 Stoeckeler & Arneman ( I960) and the Duke University 

 School of Forestry (Anon. 1959). Foliar application and 

 foliar absorption of nutrients is a relatively new field: this 

 research was reviewed by Boynton ( 1954) and by Wittwer 

 & Teubner (1959). 



The fertilization studies in pomology and forestry have 

 little direct application for the arborist and the homeowner, 

 who are interested in maintaining aesthetic appeal of shade 

 trees by improving the color, promoting more vigorous 

 growth, or restoring the condition of trees that have been 

 weakened by disease, insect attack, or unfavorable environ- 

 mental conditions. 



Early research on fertilization of shade trees was con- 

 ducted for 2 years on American elm and Norway maple 

 by Jacobs (1929) in Kent, Ohio. Jacobs applied a 

 5.75-8-3 fertilizer to established street trees approximately 

 2 inches in diameter. His results indicated little difference 

 in benefits between fall and spring treatments but a decided 

 benefit from either treatment. 



Beilman ( 1934) reported studies on shade tree feeding 

 at the Missouri Botanical Garden in St. Louis. His recom- 

 mendations are based on observations of response to appli- 

 cations of various fertilizer treatments over several years 

 rather than on controlled, replicated experiments. He con- 

 cluded that the fertilizer formulation 10-8-6 is best for 

 shade trees, which "cannot be over-fed; they require large 

 amounts of food." 



Wyman (1956) reported a study on nursery-size pin 

 oaks transplanted into a field maintained under lawn condi- 

 tions. He compared ammo-phos (15-30-0 and 11-46-0) 

 and ammonium sulfate by placing the fertilizers in holes 

 10 inches deep and 12 inches from the tree trunks on both 

 stony clay and silty clay loam soils. Three years of data 

 show that both fertilizers materially increased tree growth. 

 The ammo-phos produced a greater response than ammoni- 



Thls I'M" i i published bj authority of thi Stati of Illinois 



[RS ''i> 187 1'.,, 58 18 it is i ntrlbutlon from the Section of 



\|,|.ii,',i Uiituny .mi n I'aiiic.i.iev <>f the Illinois Natural 



Hlstorj Survej Dr K B, Himelick and Dr Dan Neelj are 

 Associate Planl Pathologists »iiii the Illinois Natural History 

 Survej Mi Webster l: Crowley, Jr., Is Head ol Applied Re- 

 sciir.li nl llio Moil. ,n Arlniri'tiiiii. Lisl.-. Illinois 



um sulfate on both soil types: in 2 of the 3 years, the 

 response was greater on the silty clay loam soil than on 

 the other type. 



Chadwick ( 1935, 1937, 1940) contributed considerable 

 information on shade tree fertilization practices through 

 his study of a block of 500 American elms. Ulmin amtri- 

 cana L. He recorded 7 years of data (1933-1939) on the 

 results from 12-6-4, 6-6-4, ammonium sulfate, and a mix- 

 ture of ammonium sulfate and superphosphate ("or an 

 approximate equivalent i applied in the spring, summer, 

 and fall to the soil surface over the entire area beneath 

 the spread of the branches. Chadwick's study indicated 

 that fall was as favorable as, or more favorable than, other 

 seasons for application of fertilizers and that complete fer- 

 tilizers were more beneficial than nitrogen alone. 



Chadwick et al. ( 1950) in a test on Norway maples, 

 Acer platanoides L., evaluated various methods of fertiliz- 

 ing shade trees. The trees, averaging 1.5 inches dbh at 

 the start of the experiment, had been planted in the test 

 plot in the fall of 1935. They were fertilized in 1941 and 

 again in 1947. Trunk diameters were recorded annually, 

 the last time in 1948. The greatest increase in diameter 

 resulted from surface application of a complete fertilizer to 

 a mulch, 2 to 5 inches deep, of rotted stable manure around 

 each tree. The complete fertilizer alone (without peat or 

 stable manure) produced better results when applied to the 

 surface than when placed in holes made by a drill or crow- 

 bar. There were no significant differences between the other 

 methods of application: fertilizer applied with air or water, 

 or both air and water, in drilled holes, or fertilizer placed 

 in holes made with a crowbar. In plots from which one 

 or more of the nutrient elements had been omitted, nitrogen 

 was considered the limiting element: when phosphorus 

 was added to nitrogen, a greater stimulation resulted than 

 from nitrogen alone. 



Pirone (1951) reported experiments in New York 

 City with foliar application of nutrients to more than $00 

 street trees of five species. He noted that the general 

 appearance of treated trees was better than that of un- 

 treated trees. His chemical analyses of leaves from a small 

 number of London plane trees and pin oaks showed more 

 of both nitrogen and phosphorus in leaves from the treated 

 trees than in leaves from the untreated trees. He concluded 

 that both nitrogen and phosphorus can be absorbed directly 

 by leaves and are of benefit when applied as foliar sprays 



The investigation reported here was initiated to com- 

 pare and evaluate current shade tree fertilization recom- 

 mendations concerning formulations and methods of ap- 

 plication. It is expected to form the basis for future shade 

 tree research relating soil fertility and tree vigOI to certain 

 physiological and pathological diseases 



