The above-ground part of a plant has an important contribution to plant development and yield production. Physiological activities of a plant canopy highly correlate to morphology of plant vegetation. Obviously, leaf area index is a good indicator for leaf area, but does not provide any information about the spatial architecture of plant canopy. With the development of fractal theory, a quantitative toot is now available for the investigation of complex objects and shapes such as plant structure. Vegetation structure of corn ( Zea mays L.) and soybean (Glycine max. (L.) Merr.] plants might be affected by the plant population density (low, normal, high) of each crop and corn-soybean intercropping. Skeletonized leaf-off images provided acceptable information to estimate the fractal dimension of the soybean plant 2-dimensionally, using the box-counting method. Fractal dimension varied among soybean treatments, with rankings: low > normal > intercrop > high, in the overall mean and normal ≈ intercrop ≈ low > high, in the slope of time plots. An adjustment of field corn plants to treatments, by changing the orientation of the plane of developed leaves with respect to the row, was observed. Thus, the fractal dimension of corn plant skeletal images from each of two sides, side I (parallel to row) and side 2 (perpendicular to row), was analyzed. On the basis of overall means of fractal dimension, treatments were ranked as: high > normal ≈ intercrop ≈ low for side 1 and intercrop > low ≈ normal > high for side 2. In both cases of soybean and corn plants, leaf area index, plant height and number of leaves (only in case of soybean plant) increased over the experiment for all the treatments, indicating a positive correlation with fractal dimension. In contrast, light penetration decreased during crop development, indicating a negative correlation with fractal dimension. Furthermore, a modified version of the Beer-Lambert equation, in which fractal dimension mu

Thesis (Ph. D.)--Oregon State University, 1989. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph.D.)--University of Alberta, 2010. / Title from PDF file main screen (viewed on May 27, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Plant Science, [Department of] Agricultural, Food and Nutritional Science, University of Alberta. Includes bibliographical references.

Thesis (M.Sc.)--University of Alberta, 2010. / Title from PDF file main screen (viewed on May 28, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Rangeland and Wildlife Resources, Department of Agriculture, Food and Nutritional Science, University of Alberta. Includes bibliographical references.

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Experiments were performed to determine the nature of maize influence on bean disease in additive-type intercrops. Overall effects of intercrops on angular leaf spot (caused by Phaeoisariopsis griseola) in Kenya indicated >23% reductions (P<0.05) in area under the disease progress curve (AUDPC) in two of three season-site combinations. Fertilization tended to increase disease (135-205%, P<0.10), but changes in bean density or planting pattern had no effect. Intercrops reduced temperature and wind velocity, but increased relative humidity. A 27% AUDPC reduction (P=0.07) in bean rust (caused by Uromyces appendiculatus) due to intercropping was observed in Oregon in 1989 and 1990 in two of three locations. Mechanisms of maize influence on rust were also assessed in Oregon. Intercropping, and competition of maize with beans alone, consistently steepened dispersal gradients (P<0.10). Interference of maize with dispersal alone tended to flatten gradients. Spore retention in plots was increased in mid-season, then decreased late in the season, due to competition in both years (P<0.05). Intercropping reduced infection by 96% late in 1989 (P<0.05), probably due to microclimatic influence of maize. The data from these experiments were used as inputs for computer simulation to evaluate effects of specific mechanisms on disease dynamics. Combination of all mechanisms (= intercrop) reduced AUDPC to 32% of monocrop, using 1989 data. Infection efficiency reductions, and to a lesser extent dispersal effects, were responsible for these changes. Intercrop effects declined as pathogen multiplication rate (DMFR) increased. No intercrop effect occurred at any DMFR using 1990 data, although interference and competition effects of maize alone both increased AUDPC at low DMFR. Partitioning dispersal effects into those due to gradient slope changes and spore retention indicate that the latter accounts almost entirely for disease alteration. / Graduation date: 1992

Monoculture corn (Zea mays L.) production may result in increased soil degradation through intensive cultivation and N fertilizer use. Intercropping may reduce these negative effects. The objectives of the study were to examine at two sites the effects of monocropping and intercropping corn on soft physical and chemical properties. A sandy loam soil of the Chateaugay series and a sandy loam soft of St Dainase series were used in a field experiment for 1993 and 1994 growing seasons. Soil with corn monoculture planted at 60 and 90 cm row width had lower soil, organic matter than that under intercrops. Soil aggregate stability treatment effects varied with soil. Corn intercropped with perennial rye grass (Lolium perenne L.) showed the highest of aggregate stability. Similar trends were noted with wet-sieved aggregate diameters. Monoculture corn tended to produce higher soil bulk density than intercrops. There was some evidence of compaction after late seeding of intercrops. Monoculture corn resulted in more acidity and lower pH than corn with intercrops. Extractable P and K by Mehlich III were lower in monoculture corn than corn-soybean intercrops. Intercropping tended to reduce residual soil NO3 -- levels but this effect varied with depth. Single and broadcast N application resulted in higher N residues with corn planted at 75 cm row width than split and banded application. Intercropping tended to reduce soil degradation and pollution as measured by aggregate stability and NO3 -- residues.