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Title: Soil denitrification : effect of oxygen and moisture and measurement in the field
Creator: Sexstone, Alan John
Date: 1983
Collection: Electronic Theses & Dissertations

Title: Soil factors affecting the growth of carnations
Creator: Rawson, Jesse Melvin, 1915-
Date: 1953
Collection: Electronic Theses & Dissertations

Title: Soil factors influencing arsenic soil tests and growth of selected turfgrasses
Creator: Carrow, Robert N.
Date: 1972
Collection: Electronic Theses & Dissertations

Title: Soil fungistasis : Sensitivity of spores ; mechanism in reinoculated sterilized soils
Creator: Steiner, Gary W.
Date: 1968
Collection: Electronic Theses & Dissertations

Title: Soil fungistasis : nature of the inhibition of nutrient-independent propagules
Creator: Bristow, Peter Richard, 1946-
Date: 1974
Collection: Electronic Theses & Dissertations

Title: Soil invertebrate interactions with microplastic pollution
Creator: Helmberger, Maxwell Summit
Date: 2022
Collection: Electronic Theses & Dissertations
Description: Microplastics are an unfortunate byproduct of human society’s increasing reliance on synthetic plastics for packaging, clothing, and other products. Microplastics have long been known to pollute the world’s oceans, but recent work has shown them to be just as prevalent, if not more so, in soil. Early findings indicate similar potential for harm to soil organisms as has been seen for marine microplastics. Yet aside from microplastics’ direct physical and toxicological effects on soil organisms...
Show moreMicroplastics are an unfortunate byproduct of human society’s increasing reliance on synthetic plastics for packaging, clothing, and other products. Microplastics have long been known to pollute the world’s oceans, but recent work has shown them to be just as prevalent, if not more so, in soil. Early findings indicate similar potential for harm to soil organisms as has been seen for marine microplastics. Yet aside from microplastics’ direct physical and toxicological effects on soil organisms, one must also consider their interactions with these organisms, the ways in which organisms may influence microplastics’ formation, occurrence, and distribution in soil as well as mediate their effects on the rest of the soil community. My research is focused on soil invertebrates’ ability to create microplastics by fragmenting large plastic debris. To advance this goal, I first developed a novel fluorescent counterstaining technique, adding a blend of Calcofluor white and Evans blue to the traditional Nile red staining approach. The counterstain allowed microplastics to be visually distinguished from chitin, cellulose, and other biological materials that may survive chemical digestion along with the plastics, making it possible to detect plastics in samples of soil invertebrate fecal material and biomass. I then investigated four soil invertebrates’ ability to generate microplastic from polystyrene (PS) foam debris. Individuals of the beetle larva Zophobas morio, the cricket Gryllodes sigillatus, the isopod Oniscus asellus, and the snail Cornu aspersum were placed in glass arenas with pieces of pristine or weathered PS foam for 24 h, after which I counted microplastic particles in the invertebrates’ fecal material, cadaver biomass, and the sand substrate of their arenas. Z. morio fragmented all plastics and produced the most detectable microplastic, C. aspersum produced almost none, and G. sigillatus and O. asellus fragmented only the weathered plastics. In a follow-up experiment with O. asellus, identical pieces of pristine PS foam were subjected to ultraviolet light, immersion in a soil suspension, and combination treatments to assess the effects of exposure to the elements on fragmentation by the isopods. Plastics immersed in the soil suspension were fragmented to a significantly greater degree than other treatments. Together, these results suggest that large plastic debris could represent a source of microplastics into soil environments, and that laboratory experiments investigating fragmentation of pristine plastics may risk underestimating the phenomenon. My further investigations focused on fragmentation of weathered PS foam by the isopods O. asellus and Trachelipus rathkii, examining fragmentation over different spans of time and the effects of natural materials as alternate substrates for the isopods. Neither species appreciably fragmented the PS foam until after 48 h, an interesting contrast to the previous experience, and O. asellus produced more fragments than T. rathkii. The presence of wood as an alternate substrate did not significantly affect fragmentation. More broadly, these results indicate that laboratory experiments should be conducted over short timescales and do not necessarily need to include alternate or supplementary food for the study organisms. In summary, the potential of soil invertebrates to affect microplastic dynamics, complicating their effects on other organisms compared to what would be seen in a standard ecotoxicological assay, should be considered when assessing this novel pollutant’s impact on soil ecosystems.
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Title: Soil layer cross-section image of how drum aerifier spoons enter and exit a soil profile
Creator: Watson, James, 1920-2013
Date: 19xx
Collection: Dr. James R. Watson, Jr. Image Archive
Description: Cross section soil profile image showing drum aerifier spoons entering and exiting the soil. Probably fake subsoil horizons.

Title: Soil moisture and soil temperature regimes in Zimbabwe : estimated from climatic data
Creator: Watson, J. P. (Of University of Zimbabwe)
Date: 1982
Collection: Zambezia

Title: Soil moisture depletion by various grasses and legumes used as orchard soils
Creator: Higdon, Roscoe John
Date: 1953
Collection: Electronic Theses & Dissertations

Title: Soil moisture regime and soil water balance under upland hardwood forest during a period of subnormal precipitation
Creator: Harlan, Richard L.
Date: 1967
Collection: Electronic Theses & Dissertations

Title: Soil nitrogen and carbon fractions as related to organic amendments and response of oats in the greenhouse
Creator: Wright, George William
Date: 1964
Collection: Electronic Theses & Dissertations

Title: Soil nitrogen availability indexes and effects of potassium carriers and levels of potassium and nitrogen fertilization on the yield and quality of sugar beets
Creator: Gascho, G. J. (Gary John), 1941-
Date: 1968
Collection: Electronic Theses & Dissertations

Title: Soil nitrogen cycling and ectomycorrhizal community composition following disturbance in Michigan jack pine forests
Creator: LeDuc, Stephen Daniel
Date: 2009
Collection: Electronic Theses & Dissertations

Title: Soil nutrient dynamics and shifting microbial processes with increasing rotational complexity in row crops
Creator: Neill, Brendan Edward
Date: 2017
Collection: Electronic Theses & Dissertations
Description: Agriculture faces pressure to supply increased food, fiber, and fuel, while provisioning ecosystem services. Intensive agriculture has contributed to altered global carbon (C) and nitrogen (N) cycles, and is the leading source of nitrous oxide (N2O), a powerful greenhouse gas. New approaches are needed to improve soil nutrient management while sustaining agricultural productivity. In natural systems a strong relationship exists between aboveground diversity and belowground ecosystem controls...
Show moreAgriculture faces pressure to supply increased food, fiber, and fuel, while provisioning ecosystem services. Intensive agriculture has contributed to altered global carbon (C) and nitrogen (N) cycles, and is the leading source of nitrous oxide (N2O), a powerful greenhouse gas. New approaches are needed to improve soil nutrient management while sustaining agricultural productivity. In natural systems a strong relationship exists between aboveground diversity and belowground ecosystem controls on nutrients. While increasing the number of crops in rotation in agroecosystems can have multiple benefits, the linkages between rotational diversity, nutrient cycling pathways, and the soil ecosystem remain poorly understood. My dissertation addresses the effects of increasing crop rotational complexity on soil C and N cycles and the soil ecosystem process that regulate them. I extend this work by testing ecosystem-based measures of soil health on Michigan farms.Long term cropping system experiments are ideal sites to examine how rotational legacy shapes belowground processes. Chapters 1, 2, and 3, focus on a cropping biodiversity experiment in place for 10 years at the initiation of my study. The gradient ranges from continuous summer annuals – corn (Zea mays L.) and soybean (Glycine max.) – to rotations that also include a winter annual (wheat; Triticum aestivum L.), to complex rotations with overwintering cover crops. This experiment has not received any external inputs such as fertilizer or pest control agents, so that changes across the gradient are narrowed to the effect of crop rotational complexity. In Chapter 1 I examine how labile C and N pools, soil enzyme activities, and soil respiration respond to increasing rotational complexity. I found that pools of potentially mineralizable C were nearly twice as high on fields with a history of cover crops, compared to those without. Rotations with a legacy of cover crops sustained higher enzyme activities, significantly higher soil respiration and accumulated significantly higher total soil organic matter.In chapter 2, I tested the relationship between increasing the number of crops in rotation and the species diversity of soil bacteria. I found no significant difference in species diversity of bacteria, but a shift in the community between rotations with and without cover crops. Taxa responsible for this shift were mainly from the Acidobacteria and the Proteobacteria which are characterized by contrasting growth and energy use strategies. I focused on denitrification in Chapter 3, a process carried out by soil microbes that produces N2O. Rotations with cover crops had significantly higher mean N2O flux over two growing seasons. Enzyme assays showed that denitrification was more efficient on these rotations, and rotations with cover crops also had a significantly higher proportion of genes in the N2O-production pathway that derived from ammonia oxidizing bacteria.Finally, in Chapter 4 I tested soil health on fields that Michigan farmers had designated as having either good or poor soil quality. Testing captured soil variability on farmer fields, but interviews with farmers revealed caveats to implementing soil health testing. My work on increasing rotational complexity revealed novel microbial controls on soil C cycling and N2O flux, but ultimately implementing practices that enhance soil ecosystem function depends on human decisions about land use, crop production, and environmental outcomes.
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Title: Soil nutrients in glaciated Michigan landscapes : distribution of nutrients and relationships with stand productivity
Creator: Merkel, Dennis Michael
Date: 1988
Collection: Electronic Theses & Dissertations

Title: Soil organic carbon dynamics and mycorrhizal fungal diversity in contrasting agroecosytems
Creator: Mpeketula, Placid Mike Gabriel
Date: 2016
Collection: Electronic Theses & Dissertations
Description: Maintenance and improvement of soil quality is critical to sustaining agricultural productivity and environmental quality. Soil organic carbon (SOC) and Arbuscular Mycorrhizal Fungi (AMF) are among key soil quality and agronomic sustainability indicators. AMF are involved in nutrient transfers and C sequestration, relevant in the global carbon cycle and greenhouse gas abatement. Conventional agriculture adversely affects SOC, AMF and the environment, yet little is known on the impact of...
Show moreMaintenance and improvement of soil quality is critical to sustaining agricultural productivity and environmental quality. Soil organic carbon (SOC) and Arbuscular Mycorrhizal Fungi (AMF) are among key soil quality and agronomic sustainability indicators. AMF are involved in nutrient transfers and C sequestration, relevant in the global carbon cycle and greenhouse gas abatement. Conventional agriculture adversely affects SOC, AMF and the environment, yet little is known on the impact of alternative options. In this dissertation, I examined the impact some options on selected soil quality indicators in temperate and tropical settings to address some existing research gaps. In Chapter 1, I examined the role of nutrient management and crop diversity on SOC and aggregate stability in a 20 year field study of the Living Field Laboratory (LFL) at KBS-LTER in Michigan. I assessed responses of Integrated Fertilizer and Integrated Compost management on a diversity gradient comprising of monoculture Corn, Corn-soy rotation, Corn-soy-wheat rotation, and Corn-soy-wheat rotation with a cover crop. Management rather than diversity exerted significant influence on SOC and labile carbon (POXC) status across treatments with higher SOC and POXC levels in compost treatments. Crop diversity exerted positive influence on aggregate stability. Diverse rotations had greater aggregate stability than monocultures regardless of nutrient management system. Thus crop diversity can enhance soil structural stability in the long term, and compost management holds promise in ameliorating both poor soil Carbon status and soil structural stability associated with continuous corn monoculture systems. In Chapter 2, I investigated AMF spore diversity using morphological techniques to assess abundance and diversity of AMF in the LFL. Proportions of AMF taxa varied with crop diversity. Surprisingly, nutrient management influenced soil organic matter but not AMF community composition across management systems. In Chapter 3, I report on the influence of land use on soil bio-resources in the tropical landscape of Machinga District in Malawi, a country in Sub-Saharan Africa. I examined communities of AMF in Miombo woodlands and croplands nested within Malosa Forest Reserve. The Shannon- Weiner diversity index (H ́) differed significantly among land use types being higher in agricultural soils than in the natural forest soils reflecting community compositional shifts among communities under study.In Chapter 4, I report on SOC spatial distribution at landscape scale in Machinga district located in sub-Saharan Africa and evaluated SOC prediction accuracy among various interpolation techniques. SOC distribution was greatly influenced by land use type and spatial topographic attributes. Overall, mean SOC content on surface layer soils declined over a period of 2 decades. Ordinary kriging with spherical semivariogram model fitting was found to be the optimal approach for investigating SOC spatial distribution and variability in the complex landscape. The study provides important contributions to the understanding of SOC spatial distribution that can guide land management policy, carbon sequestration and climate change mitigation strategies.
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