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 Title: Weed-soybean canopy apportionment as an estimation of soybean (Glycine max) development and yield loss Author(s): Pike, David Ralph Doctoral Committee Chair(s): Wax, Loyd M. Department / Program: Crop Sciences Discipline: Crop Sciences Degree Granting Institution: University of Illinois at Urbana-Champaign Degree: Ph.D. Genre: Dissertation Subject(s): Agriculture, Agronomy Abstract: Field studies were conducted from 1986 through 1988 to evaluate developmental characteristics of soybean plants growing within 100 cm of a weed and to evaluate the usefulness of weed measurements in predicting the yield losses of soybeans growing next to jimsonweed (Datura stramonium) and common cocklebur (Xanthium strumarium). Dates of soybean planting, locations, weed species, and years, were varied to evaluate the impact of environment on weed-crop competition. Soybean leaf area, mainstem node development and abscission were reduced as much as 10 percent in plants growing within 20 cm of the weed base; these reductions were not well correlated with final soybean yield. The mean yield of all soybean plants growing within 100 cm of the weed base varied from 0 to 26 percent among treatments and was highly correlated with the total projected leaf area of the weed as viewed from a camera directly over the weed-crop canopy (r$\sp2$ = 0.88). The seed yield of these same soybean plants was not so well correlated with actual weed leaf area (r$\sp2$ = 0.46) and weed diameter (r$\sp2$ = 0.80). The average yield of the soybean plants within 20 cm of the weed reliably predicted the mean yield of all soybean plants within 100 cm of the weed (r$\sp2$ =.86). A linear function model for soybean growth within the area of weed influence was generated and found to approximate actual field measurements (r$\sp2$ = 0.96). This model was based upon the selection of the data point from plants nearest the weed and from a point on a three-point moving average 80 cm from the weed. Issue Date: 1989 Type: Text Language: English URI: http://hdl.handle.net/2142/21680 Rights Information: Copyright 1989 Pike, David Ralph Date Available in IDEALS: 2011-05-07 Identifier in Online Catalog: AAI8924919 OCLC Identifier: (UMI)AAI8924919
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