Thesis
Cover crops and weed dynamics in organic reduced tillage
Washington State University
Master of Science (MS), Washington State University
2013
Handle:
https://hdl.handle.net/2376/103773
Abstract
Organic reduced tillage using cover crops as grown-in-place mulch for weed management offers environmental benefits but presents management challenges. Reduced tillage organic agriculture can improve soil quality, reduce fossil fuel use, and lessen reliance on chemical fertilizers and pesticides; thus there is interest in its adoption. However, many management options for cover cropping are not well understood, including the impacts of termination method, termination timing, and cover crop variety choice. Two field experiments and a greenhouse trial were conducted to assess the influence of cover crop management choices on soil nitrate and weed germination in western Washington. The goal of the first experiment was to determine the effects of cover crop biomass production, soil nitrate, and light penetration on weed counts in barley, vetch, and a barley-vetch mix cover crop grown for mulch. Amount of light penetrating mulch was not influenced by cover crop variety. The barley supplied essentially no soil nitrate while the vetch and mix input 5.5 to 32 ppm nitrate and average number of weeds m-2 ranged from 15 to 97 at 4 weeks. There was no correlation between weeds and nitrate. The goal of the second experiment was to determine the effect of seven cover crop varieties terminated with two methods and at two different times on cover crop biomass production, effectiveness of cover crop termination, soil nitrate, and weed percentage cover. Cover crop biomass ranged between 3 to 8 Mg ha-1 and soil nitrate ranged from 4.5 to 71 kg ha -1 . Rye varieties were more v effectively rolled than the barley. Weed cover significantly influenced weed cover at the "late" termination time only and soil nitrate did not strongly influence weed cover for any cover crop varieties. In the related greenhouse experiment, mulch depth had a greater effect than cover crop variety on weed germination. The results of these studies indicate that cover crop biomass and termination timing are important factors influencing weed cover and termination effectiveness and that there is no correlation between the increased soil nitrate from a legume cover crop compared with non-legume varieties.
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Details
- Title
- Cover crops and weed dynamics in organic reduced tillage
- Creators
- Sandra Sophia Wayman
- Contributors
- Craig G. Cogger (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Crop and Soil Sciences, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525059701842
- Language
- English
- Resource Type
- Thesis