Theses and Dissertations at Montana State University (MSU)
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Item Restoring semi-arid lands with microtopography(Montana State University - Bozeman, College of Agriculture, 2019) Dillard, Shannon Leigh; Chairperson, Graduate Committee: Anthony HartshornWater is often limiting to plant establishment in semi-arid lands, and this limitation can be especially pronounced in restoration contexts where human legacy impacts and/or non-native plants are present. The application of herbicide and mulch can help retain soil moisture by killing unwanted plant species or lowering evaporative losses, respectively. Creation of microtopography, or soil surface variation, is a third technique that could alleviate growing-season water shortages. Here we report findings from a study that explored the effects of these three techniques combined with broadcast seeding a mix of four native grasses, one native shrub, and one native forb for increasing plant canopy cover and density at three sites in northern Yellowstone National Park. One year after treatment, plant cover in control plots averaged 60%. Across plots treated singly with 1.5% glyphosate herbicide, 3 cm of red cedar mulch, or hand-dug microtopography, only mulch and microtopography increased canopy cover relative to control plots, although the increase consisted mostly of non-native species (>97%). Herbicide, not surprisingly, decreased canopy cover, and that decrease also consisted mostly of non-native species. The herbicide treatment was the most effective in encouraging native species canopy cover and density while simultaneously reducing the same measures of non-native species. Microtopography treatments encouraged growth of all plants (native and non-native), particularly in the micro-lows, but for this to be an effective restoration strategy, non-native species must first be controlled. Although herbicide was quite effective at reducing non-native species populations, particularly at the Cinnabar site, spraying must be timed with the phenology of the existing non-native plant community. We learned that reducing competition with non-native plants does not necessarily encourage native plant growth, which may indicate that growing conditions need to be improved at this site before restoration can be successful. Taken together, our results suggest that soil amendments like microtopography and mulch may have beneficial restoration applications in semi-arid lands but may also show little benefit on a short time-scale in a highly disturbed system. Areas plagued by non-native species invasions and legacy agricultural and grazing impacts are likely to require careful planning of restoration approaches in order to claim long-term success.Item The ecology of nutrition : managing soil organic matter to supply soil nutrients, increase soil biotic activity and increase crop nutritive value(Montana State University - Bozeman, College of Agriculture, 2014) Neff, Karin Stockton; Chairperson, Graduate Committee: Catherine A. Zabinski; Bruce D. Maxwell and Catherine A. Zabinski were co-authors of the article, 'Input C:N effects on soil fertility and spinach yields over three years' submitted to the journal 'Agriculture, ecosystems and environment' which is contained within this thesis.; William E. Dyer, Bruce D. Maxwell and Catherine A. Zabinski were co-authors of the article, 'Organic matter effects on spinach antioxidant production' submitted to the journal 'Journal of the science of food and agriculture' which is contained within this thesis.; Karin Neff, Bruce D. Maxwell, Clain Jones, Elizabeth Hummelt and Catherine A. Zabinski were co-authors of the article, 'Estimating plant available nitrogen in organic market garden systems' submitted to the journal 'Soil biology and biochemistry' which is contained within this thesis.; Bruce D. Maxwell, Katie Atkinson and Catherine A. Zabinski were co-authors of the article, 'Thinking like a microbe: the biological mechanisms of fertility in sustainable mixed-vegetable production' submitted to the journal 'Applied soil ecology' which is contained within this thesis.The increasing consumer interest in high quality foods -especially fruits and vegetables with high antioxidant phytochemicals -has led to interest in determining the effects of cropping system practices on phytochemicals over the last decade. Appropriate fertility management is critical to optimize agricultural production, both for yield and crop nutritive value, and minimize losses to the environment. In organic production systems, fertility management generally relies on soil microbial processes to decompose organic matter. To better understand the dynamics of mulch decomposition and the resulting effects on soil fertility and crop yield, a three-year randomized strip-plot experiment was implemented on the Montana State University Horticulture Research Farm. Two mulch inputs with varying carbon to nitrogen ratio (C:N), decomposition rates and microbial responses were contrasted with two non-mulched treatments, urea N fertilizer and a no-treatment control. Spinach biomass, yield, total phenolics and antioxidant capacity were measured as plant response variables to changes in soil fertility and biology due to the different inputs over three years. Water-extractable organic matter (WEOM), available nitrogen (N), phosphorus (P) and potassium (K), carbon (C) respiration, N mineralization, soil enzyme activity, microbial biomass and mycorrhizal infectivity potential were measured to assess soil fertility and biology. The hay mulch treatment increased nutrient availability and soil biological responses, and produced high spinach yields. The straw mulched treatment had a delayed effect on N availability and lower spinach yields initially, but in subsequent years both yield and biological parameters increased in the straw mulched treatments. Both mulch treatments produced cumulative spinach yields comparable to or exceeding the N-fertilizer plots. Only slight differences in total phenolic concentration and antioxidant capacity were measured among treatments indicating that other factors likely influence spinach phytochemicals more strongly than SOM. Measuring biological responses can be a sensitive measure of soil function and an important addition to farm management to better estimate how different management practices will affect soil processes, yields and the environment.Item The effects of native hay mulch on stabilization and revegetation of strip mined lands in southeastern Montana(Montana State University - Bozeman, College of Agriculture, 1983) Darling, Andrea Purmort