Browsing by Subject "Root"
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Item Below-ground plant residues as a source of nitrogen in double-crop forage systems(2016-09) Raskin, DanielDouble-cropping with forages can increase yields and N-use efficiency over sole-crop systems, but reductions in primary crop yield can limit economic returns. This study assessed whether the combination of high value, forage, early maturing corn varieties, and reduced N inputs constitutes an economically viable, low N-input double crop system for Minnesota. Biomass yield, N uptake, and residual soil N were measured in two double-crop (DC) and one sole-crop (SC) systems at site-years in MN, from 2014 to 2016. In DC treatments, a pea- (Pisum sativum L.) barley (Hordeum vulgare L.) forage bi-culture was double-cropped with early-maturing hybrid (DC-HC) or semidwarf (DC-SD) corn (Zea mays, L.) varieties. In SC treatments, full-season hybrid corn (SC-HC) was planted with no preceding forage. Corn was supplied with 6 N rates (0 to 224 kg N ha-1 for each yield component. Corn yielded less biomass in DC-HC (8.2 Mg ha-1) and DC-SD (1.8 Mg ha-1) treatments yielded compared to SC-HC (16.3 Mg ha-1). Biomass yield deficits lowered corn N demand in DC-HC treatments so that N rates >166 kg N ha-1 did not limit biomass yield in DC-HC treatments, where SC-HC corn was limited by N rate in three of four site-years. Total biomass accumulation was similar between DC-HC and SC-HC treatments when forage bi-culture yielded >7 Mg ha-1. This suggests that double-cropping with high-quality forages may constitute an economically viable low N-input alternative to sole-crop corn production in Minnesota.Item Drivers of root and fungal litter decomposition: implications for soil carbon cycling(2021-05) See, CraigGlobally, soils contain more carbon (C) than vegetation and the atmosphere combined. Despite clear importance to the global C budget, estimates of C fluxes into and out of soils remain highly uncertain. Decomposition is the dominant process by which C is lost from soil, but most of what is known about the controls of this process comes from studies of leaf litter at the soil surface. My first two chapters explore factors affecting the decomposition of two common belowground litter types. Chapter one is a global meta-analysis of the drivers of fine root decomposition, and is the first to explore the effects of species-level traits in addition to climate and substrate chemistry. My second chapter describes an experiment characterizing the dynamics and chemical drivers of fungal necromass decomposition, an important and understudied flux of soil C. My final chapter focuses on the role of soil fungi in the formation of “stabilized” soil C in the form of mineral associated organic matter (MAOM). Here, I call into question the current assumption that new MAOM formation in soil occurs in close proximity to root surfaces. Using quantitative estimates of fungal exploration, I put forth the hypothesis that fungal hyphae play an underappreciated role in distributing C through soil, and that hyphal contact with minerals encourages the formation of MAOM. This work suggests that current potential for MAOM formation in soils is significantly underestimated by not accounting for the impact of fungi.Item The influence of vegetation and root density on erosion for Three Streams in Minnesota(2013-08) Underhill, Benjamin LawrenceStreambank erosion is a growing concern in Minnesota as hydrologic conditions continue to change throughout the state. Plant root anchoring and surface protection from vegetation play a role in reducing erosion. The Rosgen Bank Assessment for Non-point source Consequences of Sediment (BANCS) method of erosion prediction uses both root density and surface protection to estimate the resistance of a streambank to erosion. In order to understand how different types of vegetation can influence parameters within the BANCS system thirty sites were selected in the Glacial Lake Plain, Glacial Till, and Loess regions. Root sampling and vegetation surveys revealed no correlation between root density and erodibility factors from the BANCS system. Data from this study can assist restoration efforts in these regions in order to improve or refine current practices, reduce erosion and improve water quality.Item Persistent pain following root canal therapy-a nested case series study(2013-08) Sobieh, RadwaIntroduction: Persistent pain following root canal treatment (RCT), a common dental procedure, can be either of odontogenic or nonodontogenic origin. The prognosis for patients experiencing such pain is dependent on differentiating patients into these 2 categories and deriving specific diagnoses, since appropriate treatment various dramatically. This study aims to present the proportions of specific diagnoses these patients have and provide information about their signs and symptoms, including radiographic findings. Methods: This study was nested within a parent prospective observational study that followed up patients for 6 months following RCT. Patients meeting criteria for persistent pain at 6 months and living in Minnesota were considered eligible cases. Cone-beam Computed Tomography (CBCT) and dental radiographs were obtained and patients were individually evaluated by an endodontist and an orofacial pain practitioner to derive consensus diagnoses. Results: A total of 38 patients met the criteria, of which 19 were evaluated. Odontogenic reasons for persistent pain occurred less frequently than nonodontogenic reasons (42% vs. 53% respectively). There was an overlap of odontogenic and nonodontigenic reasons in 10% of the patients. About 16% reported some level of pain that seemed to be related to normal "healing". Of patients with odontogenic reasons, about one third was related to the previously treated tooth and the other two thirds were related to adjacent teeth. Temporomandibular pain disorder (TMD) was the most common nondontogenic reason for pain, comprising 42% of all patients and 80% of those with nonodontogenic pain. Persistent dento-alveolar pain disorder (PDAP) was less common, comprising 10% of all patients and 20% of those with nonodontogenic pain.Conclusion: Data from this study help in quantifying the frequency of odontogenic versus nonodontogenic reasons for persistent pain following RCT.