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Call number: LD2668 .T4 1962 G36

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

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A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Doctor of Philosophy School of Animal, Plant and Environmental Sciences, Johannesburg, 2014 / Water hyacinth (Eichhornia crassipes) is one of the most notorious aquatic weeds in the world. Its management, despite the release of seven biocontrol agents since 1974, remains a problem in South Africa. This is often attributed to the high level of eutrophication. However, information on the effect of heavy metals or AMD on Neochetina eichhorniae and N. bruchi, which are the common and most widely established biocontrol agents in the country, is limited. In addition integrated management, which combines herbicides with biological control methods, is the current water hyacinth control method, and requires regular monitoring of the weed’s health status. This can be assessed via the canopy chlorophyll and water content, and can facilitate the decision when to intervene and what intervention measures are appropriate and timely. Hyperspectral Remote sensing (HRS) has the potential to be that monitoring tool. This thesis investigates the physiological status of water hyacinth grown with eight different heavy metals in a single-metal tub trial, three different simulated acid mine drainage (AMD) treatments in a pool trial under the influence of biocontrol agent from Neochetina spp., and in the Vaal River at the inlets of its tributaries, the Koekemoerspruit and the Schoonspruit. A hand-held spectrometer, the analytic spectral device (ASD), was used to measure reflectance. The hypothesis that HRS can detect the response of the plant to both the heavy metals and the biocontrol-induced stresses and their interactions was tested. Different spectral indices associated with the canopy chlorophyll and water content of water hyacinth were evaluated. Among these the modified normalized difference vegetation index (mNDVI) and those associated with the red edge position (the linear extrapolation and the maximum first derivative indices) were able to detect the metal, or AMD or weevil-induced plant health stresses and showed a strong positive correlation with the actual leaf chlorophyll content, measured by a SPAD-502 chlorophyll meter. Among the contaminants Cu, Hg, and Zn treatments from the single-metal tub trial and sulphate concentrations exceeding 700 mg/L in the AMD pool trial were detected by the RS as stressful to the plants. The RS also indicated that the water contamination level was greater downstream at the inlet of the Schoonspruit into the Vaal River, compared to the other sites after rainfall. These results were also consistent with actual measurements of the different plant growth parameters in all the trials and the weevils’ feeding and reproductive activities in the tub and pool trials. Thus, the results of this study indicated that the HRS has potential as a tool to assess the physiological status of water hyacinth from a remote position, which could be helpful in management of a serious national problem. The acquisition of spectral reflectance data at a larger scale, from aerial platforms, involves a complex data set with additional atmospheric interference that can mask the reflectance and which demands more complicated image analysis and interpretation. Thus, further such studies in future are recommended.

Yellow starthistle (Centaurea solstitialis L.) is an introduced Asteraceae that has become established on 10 million acres in the Pacific Northwest and California. This weed functions as an annual or short-lived perennial and depends on seeds for reproduction. Strategies of control that reduce plant fitness or lower seed production or viability may help limit the rate of spread of yellow starthistle. Previous work has shown that grazing and mowing can influence seed production. This study tested the hypothesis that proper timing and frequency of defoliation can reduce the number and viability of seeds produced. The study was conducted in Umatilla County, Oregon using a randomized block design with 4 replications of each of 4 defoliation treatments: (1) single defoliation at the bolting stage; (2) single defoliation at the bud stage; (3) two defoliations, once at the bolting stage and again at the bud stage; (4) non-defoliated control. Each of 4 blocks consisted of a 12 x 12 m area, with 16 plots measuring 3 x 3 m. Plants were defoliated at ground level using a gas-powered string-type mower. Response measurements were collected at the end of the growing season (September) following potential regrowth and included: (1) number of seedheads per plant; (2) number of seeds per seedhead; (3) number of seeds per plant; (4) number of seeds m⁻², (5) seed viability (% germination rates). Supporting measurements included: seedhead diameter; plant height, number of branches per plant; pre-dawn xylem pressure; soil moisture; and documentation of 5 biological control insect species. A single defoliation at bolting resulted in fewer seeds per seedhead, and fewer seeds per plant than non-defoliated controls. A single defoliation at the floral bud stage or repeated defoliation (bolting and again at the bud stage) resulted in equally fewer seeds per plant and fewer seeds m⁻² compared to non-defoliated controls. There was no statistical difference in percent germination of seeds among treatments. Defoliation had no effect on the infestation rates of seedheads by biological control insects. A second study examined nutrient content of yellow starthistle during 6 phenological stages from sites in Union, Baker and Umatilla Counties, Oregon during each of 2 years. Acid detergent fiber, lignin, cellulose and neutral detergent fiber contents increased through phenological development. Crude protein ranged from 16.7 to 5.0%. In Vitro dry matter digestibility ranged from 84.8% to 57.0%. Mineral nutrients P, K, CA, Mg, Mn, Fe, Cu, Zn, and Na were analyzed and determined to be adequate for maintenance needs of ewes. / Graduation date: 2002