Effect of Foliar Applications of Urea on the Physiology and Productivity of Maize
Below, Frederick Earl, Jr.
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https://hdl.handle.net/2142/71590
Description
Title
Effect of Foliar Applications of Urea on the Physiology and Productivity of Maize
Author(s)
Below, Frederick Earl, Jr.
Issue Date
1984
Department of Study
Agronomy
Discipline
Agronomy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Plant Physiology
Abstract
Maize hybrids were sprayed at various stages of development with a mixture of urea and minerals (NPKS) or urea solutions in 1981 and 1982 to determine the effect of foliar fertilization on the physiology and productivity of maize. In 1981, five maize hybrids (P3382, B73xMo17, B84xMo17, B73xB77, FS854) were sprayed with an NPKS solution at 7 days before or 12 days after anthesis to provide a total of 11.7, 3.7, 3.7, 0.5 kg ha('-1) of N, P, K and S, respectively. In 1982, three maize hybrids (P3382, B73xMo17, FS854) were sprayed with urea solutions (two separate but equal applications) at 12 and 6 days before anthesis, 9 and 15 days after anthesis, and 25 and 32 days after anthesis to provide a total of 67 kg N ha('-1). At weekly intervals plants were harvested and subdivided into leaves, stalks (including sheaths), cobs and kernels, and assayed for dry weight, reduced-N, nitrate, and total nonstructural carbohydrates. Grain yields were determined from selected plants and from a center row reserved for final yield determinations.
In 1981, the levels and changes in chemical constituents in the various plant parts and grain yields were not affected by either spray treatment. The overall lack of response to the spray treatments in 1981 was attributed to the small amounts (relative to the abundant amounts available in the soil) of nutrients applied.
In 1982, although whole plant reduced-N content at maturity was significantly increased by spray treatment in seven of nine instances, grain yields were significantly increased only for selected FS854 plants that received the second spray treatment. Grain yields of the center (yield) row were not affected by urea sprays. In all instances grain protein percentages were increased by urea sprays.
Possible adverse effects of urea sprays were indicated by the following plant responses: (a) stalk lodging was increased; (b) indigenous N metabolism was affected as judged by a temporal increase in leaf nitrate and retention of nitrate in the stalk at maturity; (c) approximately 35% of the increased N was retained in the vegetation at grain maturity; (d) harvest indices for dry weight and nitrogen were not increased; (e) the inability to increase and maintain leaf N content; and (f) the decrease in carbohydrate reserves in the stalk. Collectively these observations provide partial explanations for the general ineffectiveness of foliar N treatments in Illinois, where soil N levels are generally high.
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