Theses and Dissertations at Montana State University (MSU)
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Item Soil health response to cropping systems in semi-arid Montana(Montana State University - Bozeman, College of Agriculture, 2024) Ashford, Zane Ann; Chairperson, Graduate Committee: Catherine A. ZabinskiTraditional cropping systems in the northern Great Plains (NGP) were dominated by cereal-fallow rotations until the 1970s, resulting in increased soil erosion, decreased soil organic matter (SOM) accumulation, and declines in soil biological activity. Recent shifts toward continuous and more diverse no-till crop production attempt to increase sustainability, diversify economic opportunities, and keep up with the growing food demand without converting more land into agriculture. With a two-year study, I explored the effects of crop types in diverse, no-till, crop sequences on soil health in dryland and irrigated systems on one farm in semi-arid Montana, using biological indicators of potentially mineralizable nitrogen (PMN), soil enzyme activity (beta- glucosaminidase, beta-glucosidase, arylsulfatase, and acid and alkaline phosphatases), and permanganate oxidizable carbon (POxC), a measure of labile carbon. Crop sequences included four crop types -- cereals, oilseeds, legumes, and root crops. Root crops, namely sugar beet, drove soil responses in PMN, evident by increased plant-available N in soils following sugar beet. Soil enzyme activity, an indicator of nutrient cycling capacity, was strongly correlated with SOM, but did not follow a pattern based on crop type. Labile carbon changed in soils between years but did not respond consistently to crops. This research also explored the soil health gap by comparing soil health in cultivated systems to nearby grasslands. In a paired-site comparison on two farms in Montana, biological health indicators were 45% lower, on average, in cultivated soils compared to adjacent uncultivated soils. This difference was consistent with lower SOM averages, offering a simple assessment to quantify the maximum attainable soil health capacity within a specific agroecosystem. Soil acidification, a growing concern for producers across the NGP, contributed to 42% lower soil enzyme activity, based on four enzymes, compared to adjacent neutral pH cultivated soils. Enzyme activity was the only soil health parameter that was lower in acid soils compared to neutral pH soils, demonstrating the sensitivity of soil enzymes. Overall, these results indicate that biological soil health indicators are sensitive to changes in crop production, changing yearly, and provide farmers with the opportunity to fine- tune their management practices to meet their soil health goals.Item Cycling and storage of reactive soil carbon and nitrogen pools: management implications for semiarid crop production(Montana State University - Bozeman, College of Agriculture, 2017) Romero, Carlos Matias; Chairperson, Graduate Committee: Richard E. Engel; Richard Engel, Chengci Chen and Roseann Wallander were co-authors of the article, 'Microbial immobilization of nitrogen-15 labelled ammonium and nitrate in an agricultural soil' in the journal 'Soil Science Society of America journal' which is contained within this thesis.; Richard E. Engel, Chengci Chen, Roseann Wallander and Clain A. Jones were co-authors of the article, 'Late-Fall, Winter, and Spring broadcast applications of urea to no-till Winter wheat II. Fertilizer N recovery, yield, and protein as affected by NBPT' in the journal 'Soil Science Society of America journal' which is contained within this thesis.; Richard E. Engel, Juliana D'Andrilli, Chengci Chen, Catherine Zabinski, Perry Miller and Roseann Wallander were co-authors of the article, 'Bulk optical characterization of dissolved organic matter from semiarid wheat-based cropping systems' in the journal 'Geoderma' which is contained within this thesis.; Richard E. Engel, Juliana D'Andrilli, Chengci Chen, Catherine Zabinski, Perry Miller and Roseann Wallander were co-authors of the article, 'The oxidizable fraction of organic matter by potassium permanganate in semiarid drylands: from soils to spectra' submitted to the journal 'Ecological Indicators' which is contained within this thesis.Changes in the size and distribution of soil organic carbon (C) and nitrogen (N) pools affect the biogeochemical properties of terrestrial ecosystems; particularly in semiarid drylands where environmental constraints limit crop production. Agriculture in the northern Great Plains (NGP) of North America has undergone a tillage reduction revolution over the past 20 years; it is therefore imperative to elucidate how organic matter (OM) and fertilizer-N cycle under no-till (NT) management given its potential for providing more sustainable cropping systems and mitigating environmental losses. The objective of this dissertation was to characterize the cycling of labile, reactive pools of soil organic C and N among NT wheat (Triticum aestivum L.)-based cropping systems subjected to differing cropping intensity and fertilizer-N management. We conducted both laboratory and field experiments following the fate of 15 N-labelled fertilizer as affected by N management principles. In surface soil, microbial uptake of NH 4+ was greater than for NO 3- forms. Lower immobilization of NO 3- might therefore increase fertilizer-N availability to winter wheat relative to NH 4+ or urea-based sources. In plant tissue, fertilizer-N recovery (FNR) by winter wheat was affected by application timing of urea to the soil surface; FNR was greater for spring than late-fall and winter applications. The addition of urease inhibitor N-(n-butyl) thiophosphoric triamide improved FNR of all urea timings, but the response was greater for late-fall and winter compared with spring applications. We also examined the cycling of labile, reactive OM as affected by differing land management. Specifically, we characterized dissolved organic matter (DOM) and permanganate oxidizable carbon (POXC) concentration and composition from soil samples collected from three long-term (>10 yr) cropping field sites. Annual NT cropping increased the concentration and compositional diversity of DOM and POXC pools; higher inputs of biomass-C promoted the accumulation of fresh, plant derived DOM relative to conventional fallow-wheat management. Such enrichment translated into higher OM accretion rates within the uppermost 0-50 cm layer, likely benefiting FNR by winter wheat. Our experimental approach provided a comprehensive tool for agroecosystem evaluation at the farm level, identifying NT scenarios that can be used for sustainable management frameworks within the NGP.Item Weed populations and crop yield as influenced by the temperature and soil moisture characteristics of no-till cropping practices(Montana State University - Bozeman, College of Agriculture, 1978) Dewey, Steven ArlenItem Sensitivity of the Century model for estimating sequestered soil carbon using coarse- and fine-scale map data sources in north central Montana(Montana State University - Bozeman, College of Agriculture, 2003) Bricklemyer, Ross StanleyItem Carabid beetle (Coleoptera: Carabidae) seasonal occurrence and species composition in northern Montana cropping systems(Montana State University - Bozeman, College of Agriculture, 2000) Miller, Carin AnneItem Restoring native species to crested wheatgrass dominated rangelands(Montana State University - Bozeman, College of Agriculture, 2004) Johnson, Janel Denice; Chairperson, Graduate Committee: Bok Sowell.In the 1980's, there were an estimated 7 to 12 million ha of crested wheatgrass (Agropyron cristatum (L.) Gaertn.) in North America. Dense stands of crested wheatgrass lack species diversity, which negatively affects populations of wild mammals, birds, and reptiles. There is new interest among land managers in replacing stands of crested wheatgrass with native species for wildlife habitat, using minimal disturbance techniques such as herbicide and no-till seeding. The objectives of this project were to (1) evaluate the effects of glyphosate on crested wheatgrass and other species and (2) test seedling establishment of native grass and forb seed mixes planted in glyphosate treated crested wheatgrass sod with a no-till drill. Field trials were conducted with two herbicide application treatments and five planting treatments in 2002 and 2003 at five sites in central and eastern Montana. Crested wheatgrass biomass and seedling biomass index were collected in 2002 and crested wheatgrass, seeded species, and non-target species biomass were collected in 2003. Results from the field trials indicate that applying glyphosate in the spring was effective at reducing the biomass of crested wheatgrass for two seasons and shifting the dominance in the stands toward native or weedy species, depending on the plant and seedbank composition. Application of glyphosate increased diversity at sites with low initial diversity but not at sites with high initial diversity. Seeding was generally not successful, due primarily to lack of moisture and nitrogen. Switchgrass (Panicum mrgatum L.) and slender wheatgrass (Elymus trachycaulus (Link) Gould ex Shinners) were the most successful seeded species. Other native bunch grasses and forbs did not establish well. Because of the high cost of native seed and no-till drilling, this treatment is not recommended unless there is sufficient moisture and nutrients in the soil at the time of planting to support seedling growth.Item Understanding carbon sequestration in north central Montana dryland wheat systems(Montana State University - Bozeman, College of Agriculture, 2013) Feddema, Ryan Patrick; Co-chairs, Graduate Committee: Perry Miller and Richard E. EngelAgricultural management practices that reduce tillage and/or increase crop intensity have been shown to promote soil carbon sequestration in many regions of the Great Plains. Comparatively little information is available on the impact of these practices on soil organic carbon (SOC) in Montana's semi-arid climate. The objective of this research was to measure rates of change in SOC in cropland for north central Montana's Golden Triangle related to conversion of crop-fallow to annual cropping, conversion to no-till management, and the implementation of both simultaneously. A second objective was to measure differences in soil microbial biomass carbon (SMBC) as an "early indicator" for soil carbon accrual after six years of management. Field experiments were established at six farm sites in fall 2002. Soil organic C was not affected by the treatments at three of the six sites after six years (2002-2008). Three of the six sites had soil carbon accrual associated with annual cropping ranging from 0.19 to 0.53 Mg ha -1 yr -1. Only one site showed soil carbon accrual associated with no-till management, accruing 0.26 Mg ha -1 yr -1. It proved unreliable to make quantitative comparisons for samples from different collection times using SMBC because stored soil samples had diminished SMBC correlated with months in storage, making it impossible to compare accurately freshly obtained SMBC with earlier baseline values from stored soil samples. It was concluded that annual cropping is likely to increase SOC in many instances; however a longer study period may be required to understand SOC response to soil management in this region.Item Diversity, spatial patterns, and competition in conventional no-tillage and organically managed spring wheat systems in Montana(Montana State University - Bozeman, College of Agriculture, 2007) Pollnac, Fredric Winslow; Chairperson, Graduate Committee: Bruce D. Maxwell.The long term sustainability of agricultural systems has become a major concern. In light of this, interest in integrated weed management systems has increased. A better understanding of ecological processes occurring within the weed community might yield insights into how to control weeds while reducing chemical inputs. The objectives of this study were to 1) compare weed species richness and diversity between conventional no-till and organic spring wheat systems, 2) compare spatial patterns of the weed community between these two systems, and 3) examine the joint effects of weed species richness and density on spring wheat performance. Objective 1 was carried out on experimental plots and three production farms in Montana. A nested plot sampling design was used to generate species-area curves. The intercept and slope of the species-area curves were then used to estimate relative α and β diversity respectively. Data indicated higher species richness, α and β diversity in organic systems. We concluded that levels of α and β diversity may serve as indicators of underlying processes occurring in these two systems.