Theses and Dissertations at Montana State University (MSU)
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Item Spatial patterns in soil depth and implications for offseason nitrogen dynamics in dryland wheat systems of central Montana(Montana State University - Bozeman, College of Agriculture, 2022) Fordyce, Simon Isaac; Co-chairs, Graduate Committee: Clain Jones and Craig Carr; Pat Carr, Clain Jones, Jed Eberly, Scott Powell, Adam Sigler and Stephanie Ewing were co-authors of the article, 'Exploring relationships between soil depth and multi-temporal spectral reflectance in a semi-arid agroecosystem: effects of spatial and temporal resolution' submitted to the journal 'Remote Sensing of environment' which is contained within this thesis.; Pat Carr, Clain Jones, Jed Eberly, Rob Payn, Adam Sigler and Stephanie Ewing were co-authors of the article, 'Spatiotemporal patterns of nitrogen mineralization in a dryland wheat system' submitted to the journal 'Agriculture, ecosystems, and environment' which is contained within this thesis.Shallow soils (< 50 cm) under dryland wheat (Triticum aestivum L.) production lose large amounts of inorganic nitrogen (N) to leaching. Crops grown in shallow soils may be more responsive to N fertilizer due to lower fertilizer recovery and suppressed mineralization, raising questions as to whether standard practices of N fertilizer rate determination can increase risks of leaching and groundwater contamination in these environments. Mineralized N can be a major nutritional supplement for wheat crops in dryland agroecosystems, so accurate estimates of mineralization inputs can have important economic and environmental implications. To assess the potential for suppressed N mineralization in shallow soils, we used spectral reflectance from up to three sensors (unmanned aerial vehicle, National Agricultural Imagery Program, and Sentinel 2) to spatially characterize soil depth on three fields in Central Montana (Chapter 2) and compared surface (0-20 cm) carbon and N cycling indices across soil depth classes (Chapter 3). Carbon dynamics were stable across depth classes while N mineralization was lower in the shallow class. Results confirm multispectral imagery as a valuable tool for non-destructively characterizing fine-scale spatial patterns in soil depth and corroborate previous findings of lower N mineralization in shallow soil environments. Given the potential for heightened fertilizer responsiveness due to lower mineralization in these environments, decision support systems for site-specific fertility management (e.g., variable rate fertilizer application) should assess the environmental consequences of leaching alongside the economic benefits of applied fertilizer rates which maximize responses of yield, quality and same-year net revenue.Item Integrating crop diversity, forage crops, and targeted grazing to manage Avena fatua L.(Montana State University - Bozeman, College of Agriculture, 2021) Wong, Mei-Ling; Chairperson, Graduate Committee: Fabian D. Menalled and Tim F. Seipel (co-chair)Wild oat (Avena fatua L.) is one of the most difficult weeds to manage in spring cereal crops and causes large economic losses throughout the Northern Great Plains. The continual use of herbicides for wild oat management has selected for herbicide resistant and multiple herbicide resistant biotypes and has left no selective herbicide options for farmers in small-grain fields. To sustain crop production, this thesis aimed to develop ecologically based practices to manage wild oat populations. We evaluated the impact of spring wheat height, seeding rate, crop type, forage termination method, and tillage on wild oat tiller density, biomass, and seed production. Two studies were conducted: (1) from 2017 through 2019 in Bozeman, Montana and (2) from 2018 through 2019 in Moccasin, Montana. The first study examined the combined effect of spring wheat height and seeding rate on its competitiveness against wild oat. We found that the tall near-isogenic wheat line did not have greater wild oat suppression than the short line. Spring wheat seeded at a higher than recommended rate reduced wild oat biomass and seed production only when nitrogen fertilizer was applied. The second study assessed management practices including integrating lentil, fall and spring forage mixture, sheep grazing and tilled fallow, in addition to spring wheat height and seeding rate. Forage mixtures, sheep grazing, and tillage were the most successful tactics in suppressing wild oat growth and seed production. However, wild oat suppression was not different between spring wheat and lentil, regardless of spring wheat height and seeding rate. Our results indicate that spring wheat height was not correlated with increased suppression of wild oat. A higher seeding rate of spring wheat also did not increase wild oat suppression; we suggest that fertilization may be needed to enhance crop competitiveness. Integrating forage crops with sheep grazing has the best potential to reduce the wild oat seed bank. This information can help redesign cropping systems. However, there is a continual need to develop other integrated weed management techniques to limit wild oat growth and seed production and to reduce reliance on herbicides.Item Assessment of host selection behaviors and oviposition preferences of Cephus cinctus Norton (Hymenoptera: Cephidae) using wheat and smooth brome(Montana State University - Bozeman, College of Agriculture, 2020) Bhandari, Rekha; Chairperson, Graduate Committee: David K. Weaver and Tracy M. Sterling (co-chair)Wheat stem sawfly, Cephus cinctus Norton (WSS), is an important pest of cereal crops in Northern Great Plains. Smooth brome has historically been suggested as a potential trap crop around wheat fields in Montana. The objective of this study was to compare oviposition preference and selection behaviors of female WSS and measure subsequent larval survival in wheat and smooth brome stems. We compared infestation, parasitism and larval development of WSS using field transects in smooth brome and adjacent wheat fields. We found no clear difference in infestation between the two host plants. There was greater larval mortality and less tunneling in smooth brome stems compared to wheat at a site near Big Sandy, Montana. At a second site near Big Sandy, there was greater infestation in smooth brome compared to wheat, but there were more dead larvae and greater parasitism in smooth brome. In Y-tube olfactometer studies, WSS females were more attracted to volatiles emitted by smooth brome than wheat. In greenhouse trials, the observation of specific behaviors leading to oviposition indicated differences in duration of ovipositor insertion and in number of ovipositor insertions that favored greater oviposition in smooth brome, but only by emergence of the first awn of the inflorescence (Zadoks 49 growth stage). There were different numbers of eggs in smooth brome stems relative to wheat, with no difference in the proportion of infested stems in choice tests conducted for two days at Zadoks 49. In no-choice tests, there were differences in both infested stems and in the number of eggs in stems at Zadoks 49. We found significantly greater amounts of key behaviorally active compounds used by female WSS, like (Z)-3-hexenyl acetate and beta-ocimene, that were among the few differences in the amounts of volatile compounds collected from two plant species. The greater amount of these compounds leads to more eggs that subsequently experience greater larval mortality in young plants, resulting in fewer cut stems in mature plants. Our findings support the consideration of smooth brome for use in trap crops to improve integrated pest management strategies for WSS.Item Potential for and implications of cover cropping and grazing cover crops in wheat agroecosystems in Montana(Montana State University - Bozeman, College of Agriculture, 2017) Walker, Robert Matthew; Chairperson, Graduate Committee: Perry MillerGrowing interest in cover cropping may provide a way to recouple crop and livestock production in semiarid Montana. This two-year field study examined edaphic and agronomic implications of cool- vs warm-season cover cropping, with and without grazing, compared to the grower standard practice of chemical-fallow. After one year of cover cropping/grazing, Olsen-P and acid phosphatase activity were higher in cover cropped/grazed treatments than the fallow treatment. Potentially mineralizable Nitrogen was higher in spray-terminated cover crop treatments than graze-terminated treatments, while soil Nitrate-N was statistically lower in cover cropped/grazed treatments than in the fallow treatment. Wheat yields were not statistically different between cover cropped/grazed and the fallow treatments; however, the fallow treatment had higher wheat seed protein than cover cropped/grazed treatments. This research also utilized the Land Suitability Analysis approach to examine four exemplary Montana counties for: 1) warm-season cover crop adoption; 2) integrated crop-livestock adoption; and, 3) warm-season cover crop use as forage in an integrated crop-livestock adoption. Fergus and Fallon Co.'s both contain portions of land highly suitable for warm-season cover crop production, while all four counties have areas where integrated crop-livestock systems appear to be a logistical possibility. The conclusions taken from this research - both the agricultural field experiment and land suitability analysis - will help inform land managers across Montana's agricultural community about these emerging practices in sustainable agriculture.Item Surface-atmosphere exchange of carbon dioxide, water, and heat across a dryland wheat-fallow rotation(Montana State University - Bozeman, College of Agriculture, 2015) Vick, Elizabeth Segourney K.; Chairperson, Graduate Committee: Paul C. Stoy; Paul C. Stoy was co-author of the article, 'The influence of dryland agriculture wheat-fallow rotation on the exchange of carbon, water, and heat with the atmosphere' submitted to the journal 'Journal of agriculture, ecosystems and environment' which is contained within this thesis.Summerfallow - the practice of keeping a field out of production during the growing season - is a common practice in dryland wheat (Triticum aestivum L.) cropping systems, including those of Montana. It is currently unknown how seasonal patterns of carbon dioxide, water, and heat flux between ecosystems and the atmosphere differ between fallow and wheat. This study quantifies the impact of dryland wheat vs. chemical fallow agricultural management practices on these important surface-atmosphere exchanges using the eddy covariance method across a winter wheat - spring wheat - fallow rotation in the Judith Basin, MT. I used a suite of meteorological sensors to measure relative humidity, air temperature, soil moisture, wind speed and direction, incident and reflected shortwave radiation, upwelling and downwelling longwave radiation, crop height, and soil heat flux to further quantify the impacts of this cropping sequence on biophysical attributes of the land surface and to model turbulent fluxes. Both wheat fields were carbon sinks on the order of 110 to 205 g C m -2 during the April to September study periods of 2013 and 2014, while the fallow field was a carbon source to the atmosphere on the order of 135 g C m -2 during the April to September study period of 2014. Evapotranspiration (ET) was over 100 mm greater in a spring wheat field than in a simultaneously measured fallow field during the 2014 study period, and modeled maximum daily atmospheric boundary layer height was up to 800 m higher in fallow compared to spring wheat. Results demonstrate that fallow has a detrimental impact to soil carbon resources yet is less water intensive, with consequences for regional climate via its impacts on atmospheric boundary layer development and global climate via its carbon metabolism.Item The effect of osmotic stress on growth characteristics of two spring wheat varieties(Montana State University - Bozeman, College of Agriculture, 1961) Richardson, GlennItem An evaluation of plant drought stress parameters in spring wheat(Montana State University - Bozeman, College of Agriculture, 1987) Touray, Katim SeringeItem Wheat yield estimates using multi-temporal AVHRR-NDVI satellite imagery(Montana State University - Bozeman, College of Agriculture, 1999) Henry, Mari PatriciaItem Nitrogen fertilizer strategies and empirical models for rainfed spring wheat(Montana State University - Bozeman, College of Agriculture, 1994) Mahmood, ShaukatItem Quantification of Persian darnel (Lolium persicum) interference in monoculture, spring wheat, canola and sunflower(Montana State University - Bozeman, College of Agriculture, 2002) Holman, Johnathon Douglas
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