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 Title: Growth Effects of Light and Plant Competition in a High Yield Environment (Soybeans; Zea Mays) Author(s): Cripps, Reed William Department / Program: Agronomy Discipline: Agronomy Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Agriculture, Agronomy Abstract: Studies were conducted to determine the effects of light in a high yield environment on corn Zea mays L.) yields and nutrient uptake, and to explain these effects based on changes in physiology, ontogeny, and physical characteristics. Strip intercropping was experimented with as a possible cultural practice that would allow greater light penetration into corn canopies.Fluorescent lamps were placed inside the canopy of field grown corn to provide supplemental light to the lower leaves. Photosynthetically active radiation was increased an average of 52.9% in rows adjacent to the lamps and resulted in a 52.6% increase in grain yield. Plant content of nitrogen (N), phosphorus (P), and potassium (K) in the rows adjacent to the lights increased an average of 98.5, 74.1, and 39.1%, respectively.Corn was planted in a high yield environment at 6,700, 26,900, 47,800, 74,700, and 107,600 plants ha$\sp{-1}$ using equidistant plant spacings at each population. Plants were sampled periodically during the 1984 and 1985 growing seasons to determine the effects of competition for light on rates of growth and nutrient uptake. Based on dry matter accumulation rates, competition for light began affecting plant growth by 30 days after emergence (DAE) at 107,600 plants ha$\sp{-1}$, by 38 DAE at 74,700 plants ha$\sp{-1}$, and by 52 DAE at 47,800 and 26,900 plants ha$\sp{-1}$. The optimum yield, 11,800 kg ha$\sp{-1}$, was obtained with 74,700 plants ha$\sp{-1}$.Research was also conducted to study the effect of strip intercropping corn and soybeans (Glycine max (L.) Merr.). Alternating 4, 6, and 10 rows of each crop at normal and high production levels were used in 1984. In 1985 strips of alternating 4 and 10 rows of each crop and 1 row of corn alternating with 4 rows of soybeans at normal, medium-high, and high production levels were used. Strip intercropping increased corn yields but decreased soybean yields. The effects of strip intercropping on yields increased as the production level increased. Land equivalent ratio (LER) values did not significantly differ from 1.00, except for the 1 row of corn alternating with 4 rows of soybeans (1:4) which had an LER of 1.15 at the medium-high production level. Issue Date: 1987 Type: Text Description: 208 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1987. URI: http://hdl.handle.net/2142/71634 Other Identifier(s): (UMI)AAI8721620 Date Available in IDEALS: 2014-12-16 Date Deposited: 1987
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