Table 1.

A chronological summary of selected shade tree nitrogen nutrition field studies conducted in the United States during the 20th century. The publications have been grouped by author(s).

Year initiated	Tear published	Duration (years)	Author(s)	Species	Spacing	Treatment			Selected findings
Year initiated	Tear published	Duration (years)	Author(s)	Species	Spacing	Ground cover	N rate (#)	Method of application	Selected findings
1929	1929	NA^*	Beilmann	NA	NA	NA	NA	NA	Literature review.
1929	1934	5	Beilmann	Fraxinus Juglans nigra Aesculus glabra Carya ovata Quercus palustris	various	sod	024–2.5/tree	broadcast, crowbar, liquid injection	Formula for fertilizer application based on tree volume; describes deep root feeding by liquid injection.
1929	1936	7	Beilmann	same as 1934	various	sod	0.24–2.5/tree	same as 1934, trenching, post hole	Same as 1934, 10-8-6 best fertilizer; fertilize before July 1, “shade trees cannot be overfed.”
1930	1936	5	Wyman	Quercus palustris	12 by 12 ft	sod	0.2/in.caliper	broadcast, crowbar	Ammon-phos better than ammonium sulfate; fertilized trees had more secondary growth than unfertilized trees.
1930	1937	7	Pridham	Quercus palustris	12 by 12 ft	sod	not described	not described	Continuation of Wymann study; no fertilizer effects at age 7.
1934	1939	5	Pridham	Ulmus americana	not described	sod	0.1/in/ caliper	broadcast, drilled holes	Decreasing growth with age; no response to fertilizer application.
1936	1941	5	Pridham	Quercus rubra	not described	sod	0.13/in. caliper	broadcast, drilled holes	No clear tree growth response; delayed fall color development; sod growth luxuriant.
1931	1934	3	Chadwick	Ulmus americana ‘Moline’	8 by 12 ft	none	36 lb/1,000 ft² 0.25 lb/in. caliper	broadcast	Limited fertilizer response, but fall application better than spring; adequate soil moisture needed for fertilizer response.
1931	1936	5	Chadwick	Ulmus americana	8 by 12 ft	none	0.25 lb/in. caliper	broadcast	Ample soil moisture seems more important for stimulating growth in good soil than additional application of fertilizer; fall fertilizer applications best.
1941	1950	7	Chadwick	Acer platanoides	8 by 8 ft	sod	1 /4 lb/in. caliper	broadcast, punched holes, fertigator, Aero-fertil	N most limiting nutrient; broadcast is best method of application.
1947	1962	4	Curlin	Cornus florida	single tree plots	forest	0 to 297 lb/ac	broadcast	Two-year response to N application.
1959	1966	5	Finn and White	Liriodendron tulipifera	25 tree plots on 6 by 6 ft Spacing	weed	336 lb/ac	broadcast	Height increase 100%, diameter 85%, leaf color greener, delayed leaf abscission.
1956	1965	2	Neely, Himelick, and Crowley	Quercus palustris Fraxinus americana Gleditsia triacanthos var. inermis	15 by 15 ft and 8 by 8 ft	sod	61b/l,000ft²	broadcast, drill, liquid injection, foliar	N applications stimulated growth; similar growth response to different application methods.
1956	1970	5	Neely, Himelick, and Crowley	Quercus palustris Fraxinus americana Gleditsia triacanthos var. inermis	15 by 15 ft and 8 by 8 ft	sod	61b/l,000ft²	broadcast, drill, liquid injection, foliar	Continuation of 1965 study N applications stimulated growth; similar growth response to different application methods; April better than October for fertilizer application.
1972	1990	18	Smith	Tilia cordata ‘Select’ Malus ‘Snowdrift’ Acer saccharum ‘Monumental’	20 by 20 ft	sod	0, 3, 6, or 9 lb/1,000 ft² once per 3 years	broadcast, drill	Response to N fertilizer muted with age as did the effect of application method.

↵^*Not applicable.