Browsing by Subject "Fertilizer"

Now showing 1 - 4 of 4
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    Agricultural intensification and global environmental change
    (2013-08) Mueller, Nathaniel Dean
    Intensification of agricultural management has allowed substantial increases in food production on existing agricultural lands, but with major global environmental costs. This dissertation explores the global-scale possibilities and tradeoffs associated with agricultural intensification using spatial data analysis and modeling. In Chapter 2, we analyze intensification opportunities from closing yield gaps, and find that large production increases (45% to 70% for most crops) are possible. We also examine what changes to management practices may be necessary to close these yield gaps, and find these vary considerably by region and current management intensity. A sub-national, crop-specific dataset of cropland nutrient use was developed to support this analysis. Chapter 3 focuses on intensification potential in the context of climate change. We find that a moderate yield gap closure scenario could result in net yield increases across much of the globe, even in the context of circa 2050 climate change. However, the capacity for intensification to overcome climate impacts erodes considerably under uniform global temperature increases of 4-5°C. Chapter 4 examines the opportunity space for improved nitrogen (N) management. We find that a reallocation of spatial N use intensity could achieve current cereal production with ~50% less N application and ~60% less excess N. We quantify a tradeoff frontier for nitrogen use and cereal production, and discuss the potential for efficiency improvements to push the frontier forward. This dissertation highlights the importance of improving agricultural management across the globe to meet food security and environmental goals.
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    Fertilizer Guidelines for Agronomic Crops in Minnesota
    (University of Minnesota Extension, 2023-07-27) Kaiser, Daniel E
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    Management strategies for control of soybean cyst nematode and their effect on the nematode community
    (2013-06) Grabau, Zane Joseph
    Soybean cyst nematode (SCN), Heterodera glycines, is the major yield-limiting pathogen on soybean and various plant-parasitic nematodes can damage corn. Additionally, the nematode community is a useful bioindicator for soil health. In chapter 1, relevant research is reviewed. Chapter 2 describes experiments testing ten organic soil amendments at various rates for SCN control in the greenhouse. Some amendments-particularly canola meal, pennycress seed powder and condensed distiller's solubles-effectively reduced SCN populations at 40 days after planting soybeans. By 70 days after planting, SCN control by amendments was diminished. Additionally, phytotoxicity was a concern, particularly at 40 days after planting. Based on these experiments, organic soil amendments have value for SCN management, but more work is needed to optimize amendment efficacy particularly at the field scale. Chapter 3 describes the impact of tillage, granular nematicide (aldicarb or terbufos), synthetic fertilizers (NPKS combinations), and organic fertilizer (swine manure) on plant-parasitic nematodes, the nematode community, and plant yield as assessed in a corn-soybean cropping system. H. glycines, Helicotylenchus spp, Xiphinema spp, and Pratylenchus spp were the major plant-parasitic nematodes present at the sites. Tillage had only minor impacts on populations of major plant-parasitic nematode genera. While aldicarb reduced H. glycines and Helicotylenchus populations, albeit inconsistently, terbufos did not affect major plant-parasitic nematode populations. Nematicides increased soybean and corn yields under some conditions suggesting plant-parasitic nematodes impacted corn and soybean, although this impact was inconsistent. Tillage, fertilizer, and nematicide impacts on the nematode community were often site- and season-specific. Manure application compellingly shifted the nematode community to one of increased enrichment and decreased community structure. The inorganic fertilizers had minimal impact on the nematode community. Conventional tillage decreased nematode community structure based on some measures, but increased bacterivore and fungivore population densities. In contrast, aldicarb nematicide decreased bacterivore and fungivore population densities. Effects of terbufos nematicide on nematode populations and community composition were inconsistent.
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    Renewable ammonia for sustainable agriculture and energy: Process, system, and enterprise optimization
    (2021-08) Palys, Matthew
    Synthetic ammonia (NH3) used as fertilizer is essential for modern agriculture, but its production at present is fossil energy and emissions intensive. A more sustainable NH3 production alternative is to use renewable-derived electricity to obtain its precursors, specifically hydrogen (H2) from water electrolysis and nitrogen (N2) separated from air. The transformative impact of renewable NH3 is not limited to agriculture alone. Energy storage costs using NH3 are considerably lower than with H2or batteries, making it an ideal candidate for the high capacity, long duration seasonal energy storage necessitated by high fractions of renewables in the power generation mix. Internal combustion technologies which are well-developed for fossil fuel feedstocks can be easily modified to be fueled with NH3, allowing its use for controllable power generation or as a carbon neutral liquid fuel. Despite its promise, a number of challenges remain in realizing the full potential of this alternative paradigm. This thesis aims to collectively address some of these challenges through the use of mathematical optimization. The economics of small-scale renewable NH3 production for agriculture are analyzed and optimized at both the synthesis process and supply chain level. A flowsheet model is developed for optimal design and technoeconomic analysis of an absorbent-enhanced NH3 synthesis process which can reduce pressure and increase separation temperature, the main drivers of capital cost in traditional condenser-based synthesis process. Absorbent-enhanced process design optimization gives 30% lower capital costs and comparable energy efficiencies to the condenser-based process at production scales smaller than conventional by one to two orders of magnitude. Optimal deployment of this absorbent-enhanced process via wind-powered NH3 production modules in fertilizer supply chains makes renewable NH3 economically viable at approximately 25% lower conventional NH3 prices than if the traditional synthesis process is simply scaled down. The economic competitiveness of synergistic renewable NH3 production and utilization systems is maximized through combined optimal design and scheduling (CODS). These CODS models select and size the best technologies for given applications while simultaneously scheduling their operation to accommodate renewable intermittency. Performing CODS for wind-powered production of NH3 for use as fertilizer, agricultural fuel, and energy storage enabled 95% emissions reduction at a cost less than $20/tonCO2. Then, the optimal economics of H2- and NH3-based electrical energy storage were investigated for 15 locations throughout the continental U.S. which comprehensively represent its different climate-demand regions. Lowest cost systems in every location included both H2 and NH3 storage pathways and optimized the trade-off between H2's higher overall efficiency and NH3's lower storage cost. This hybrid energy storage concept was extended to combined heat and power systems in remote locations as a potential market for early adoption. Low cost, long term NH3 storage and subsequent power and heat cogeneration enabled fully renewable systems to be economically competitive with those that could purchase power and heat from conventional sources. Overall, the results of this thesis demonstrate the promise of renewable NH3 and the power of mathematical optimization in achieving its full potential.