Browsing by Author "Dr. Thomas W. Rufty, Committee Chair"

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Environmental Factors Influencing Weed Interference in Agricultural Systems
(2004-07-23) Tungate, Kimberly Denise; Dr. Thomas W. Rufty, Committee Chair
In all agricultural systems using few or no herbicides, cultural and mechanical techniques are crucial to economic viability. Further advances in non-chemical weed control will require in-depth knowledge of weed biology. The objective of new strategies likely will be to alter competitive interactions between crop and weed species. An important part of weed biology, and often the basis for competitiveness, is species response to the environment. Environmental conditions differ greatly in different parts of the world. In agricultural systems, the low nitrogen status of some soils requires most crops to be amended. Weed populations can experience a wide range of fertilization regimes from year to year due to different crop rotations. Fertilization patterns in a rotation can lead to differential growth and reproductive performance of weeds and competitiveness with crops. In research described in the first two chapters, we attempt to determine the extent that lowering parental nutrition would impact weed growth, reproduction, and offspring vigor. The purpose was to begin evaluating benefits of controlling nitrogen fertility in agronomic systems on low fertility soils. Another environmental factor that could influence weed competitiveness is temperature. The significance of temperature responses will become increasingly important in the future. Global climate change models are predicting increases in the earth's average surface temperature between 1.4- 5.8 °C during the 21st century. As temperatures increase it is conceivable that warmer temperatures will alter competitive balance between crop and weed species, intensifying weed pressures. The expression of temperature response also will be a function of other interacting factors such as the ability to acquire water and nutrients. Resource acquisition is controlled to a large extent by root growth and interactions with soil microorganisms. The third chapter of this thesis is focused on temperature responses of selected plant species from an agroecological system. The purpose was to begin assessment of possible climate change effects on weed competitiveness. All of our experiments made extensive use of the weed Senna obtusifolia due to its importance in crops in the Southeastern U.S.