Browsing by Subject "Nitrogen"

Now showing 1 - 20 of 33
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    15N labeling of amino acids in Spirodela Polyrhiza
    (2018-02-15) Evans, Erin M.; Freund, Dana M.; Sondervan, Veronica; Cohen, Jerry D.; Hegeman, Adrian D.; jewet033@umn.edu; Evans, Erin M.
    These data comprise15N stable isotopic labeling study of amino acids in Spirodela polyrhiza (common duckweed) grown under three different light and carbon input conditions which represent unique potential metabolic modes. Plants were grown with a light cycle, either with supplemental sucrose (mixotrophic) or without supplemental sucrose (photoautotrophic) and in the dark with supplemental sucrose (heterotrophic). In this study, stable isotopic labeling with 15N of S. polyrhiza allowed for estimation of amino acid pool sizes, turnover, and kinetics.
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    Below-ground plant residues as a source of nitrogen in double-crop forage systems
    (2016-09) Raskin, Daniel
    Double-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.
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    Best Management Practices for Nitrogen on Coarse Textured Soils
    (University of Minnesota Extension, 2008) Rehm, George; Lamb, John; Rosen, Carl J; Randall, Gyles
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    Best management practices for Nitrogen use in northwestern Minnesota
    (University of Minnesota Extension, 2008) Sims, Albert; Rehm, George; Lamb, John
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    Best management practices for Nitrogen use in South-Central Minnesota
    (University of Minnesota Extension, 2008) Randall, Gyles; Rehm, George; Lamb, John; Rosen, Carl J
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    Best Management Practices for Nitrogen Use in Southeastern Minnesota
    (University of Minnesota Extension, 2008) Randall, Gyles; Rehm, George; Lamb, John
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    Best management practices for Nitrogen use in southwestern and west-central Minnesota
    (University of Minnesota Extension, 2008) Rehm, George; Lamb, John; DeJong-Hughes, Jodi; Randall, Gyles
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    Best Management Practices for Nitrogen Use: Irrigated Potatoes
    (University of Minnesota Extension, 2008) Rosen, Carl J; Bierman, Peter M
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    Biogeochemistry of southwestern Lake Superior and watershed, 2017-2021
    (2023-09-28) Sterner, Robert W.; Lafrancois, Brenda M; stern007@d.umn.edu; Sterner, Robert W.; Large Lakes Observatory, University of Minnesota
    Between 2017 and 2021, 1368 water samples were collected from Lake Superior and its watershed in the region generally between Duluth-Superior and Ashland, WI. Parameters include forms of carbon, nitrogen, and phosphorus, along with total suspended solids, chlorophyll, and phycocyanin.
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    Denitrification in Agricultural Surface Waters: Quantifying the Effect of Environmental Parameters and Hydrologic Connectivity on Nitrate Uptake and Microbial Communities
    (2017-10) Tomasek, Abigail
    The development of synthetic fertilizer has led to increases in crop yields and allowed for global population growth over the past century. However, this increase in available nitrogen has greatly altered the global nitrogen cycle, including increased nitrate loading to surface water and groundwater in the Midwestern United States, with negative effects on human health and aquatic ecosystems. Therefore, there is a need for effective management strategies and an understanding of the mechanisms for nitrate transport and uptake. Denitrification, the microbiological reduction of nitrate to nitrogen gas, can be viewed as a net sink for reactive nitrogen in aquatic systems. Small areas, termed hot spots, and short time periods, termed hot moments, frequently account for a large portion of denitrification. This research focuses on identifying the environmental parameters and hydrologic regimes that promote denitrification, along with determining how parameters, denitrification rates, and microbiological communities are related at multiple temporal and spatial scales. At the finest scale, a recirculating laboratory flume was used to determine the effect of turbulence and organic carbon on denitrification rates and the microbial community. An outdoor experimental stream and flow-through basin in the Outdoor StreamLab at the St. Anthony Falls Laboratory (SAFL) were used to determine the effect of short-term inundation and periodic inundation on denitrification. At the largest scale, water and sediment samples were collected over two years from a field site in an agricultural watershed in Southern Minnesota. The objectives of this research were to: (1) determine how turbulence and organic carbon affect denitrification, (2) investigate how inundation and hydrologic connectivity leads to the formation of denitrification hot spots and hot moments, (3) quantify and correlate the driving environmental parameters of microbial denitrification and the differences in these relationships for in-channel and riparian locations in an agricultural watershed, (4) develop and evaluate functional relationships between environmental parameters and denitrification rates, and (5) identify how denitrifying gene abundances, denitrification rates, and environmental parameters are related across a hydrologic gradient from channels to riparian areas.
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    Ecology and ecosystem impacts of common buckthorn (Rhamnus cathartica): a review
    (2007) Knight, Kathleen S; Kurylo, Jessica S; Endress, Anton G; Stewart, J. Ryan; Reich, Peter B
    In this review, we synthesize the current knowledge of the ecology and impacts of Rhamnus cathartica L., a shrub from Europe and Asia that is a successful invader in North America. Physiological studies have uncovered traits including shade tolerance, rapid growth, high photosynthetic rates, a wide tolerance of moisture and drought, and an unusual phenology that may give R. cathartica an advantage in the environments it invades. Its high fecundity, bird-dispersed fruit, high germination rates, seedling success in disturbed conditions, and secondary metabolite production may also contribute to its ability to rapidly increase in abundance and impact ecosystems. R. cathartica impacts ecosystems through changes in soil N, elimination of the leaf litter layer, possible facilitation of earthworm invasions, unsubstantiated effects on native plants through allelopathy or competition, and effects on animals that may or may not be able to use it for food or habitat.
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    Ecology of Giant, Sulfur-Oxidizing Thioploca Bacteria in Great Lakes Sediments
    (2021-06) McKay, Elizabeth
    Microorganisms play a key role in regulating the cycling of carbon, oxygen, nitrogen, sulfur, and other important elements in aquatic ecosystems. Thioploca is a giant, filamentous bacteria that oxidizes sulfide and reduces nitrate, coupling the nitrogen and sulfur cycles in its benthic habitats. Thioploca can achieve high abundances in marine sediment where it is known to alter nitrogen and sulfur dynamics by removing toxic sulfide and recycling fixed nitrogen back into the sediment and water column. Thioploca can also achieve high abundances in freshwater sediments; however, its distribution and biogeochemical function are poorly understood in freshwater environments, making it difficult to determine how it impacts elemental cycling in these habitats. To analyze Thioploca abundance, factors affecting its distribution, and its biogeochemical function in the Great Lakes, I quantified Thioploca biomass and water column and sediment characteristics at 33 sites that spanned a gradient of depth and trophic conditions in the Apostle Islands region of Lake Superior and Green Bay in Lake Michigan. Sediment cores were also collected at eight of my study sites to analyze vertical Thioploca biomass distribution and sediment chemistry. Thioploca was common in both the Apostle Islands and Green Bay and reached biomasses of up to 250 g/m2 wet weight at some sites. While PCA and logistic regression analysis indicated that Thioploca may be more likely to be present under eutrophic conditions, Thioploca was also common and abundant at some oligotrophic sites in the Apostle Islands. Thioploca was more abundant in fine-grained than coarse-grained sediment, suggesting Thioploca distribution may be linked to depositional areas of lakes. At most sites, Thioploca was most abundant in the top 5 cm of sediment. Ammonia profiles in some sediment cores appear to indicate possible ammonia consumption in sediment layers with Thioploca, which suggests these freshwater Thioploca may interact with benthic nitrogen cycling differently than marine species of Thioploca. My results, along with other reports from the Great Lakes, suggest that freshwater Thioploca may be widespread throughout the Great Lakes. At the abundances observed, Thioploca is likely significantly influencing nitrogen and sulfur cycling in these areas, although many questions remain about Thioploca’s biogeochemical functioning in freshwater environments, including how it achieves high biomass in low sulfur environments, whether it reduces nitrate to ammonia or N2, and whether it promotes the recycling of fixed nitrogen or acts as a fixed nitrogen sink.
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    Effect of nitrogen on Bt gene expression in corn roots, resulting trait performance against corn rootworms (Diabrotica spp.), and transgenic hybrid performance
    (2013-01) Franz, Trisha Marie
    This study examined the impact of nitrogen rates on the expression of corn rootworm (Diabrotica spp.) resistant traits in transgenic corn engineered to express one or more of Bt (Bacillus thuringiensis Berliner) Cry protein(s). The resulting protection against corn rootworm, and the comparative performance of hybrids containing zero, one or multiple (pyramided) corn rootworm traits were evaluated. Recommended nitrogen application rates have been suggested based on economics, but not for optimal expression of Bt Cry proteins. Specifically, this experiment explored the need to shift N rates to optimize Bt trait expression, corn rootworm protection provided by different traits, and a possible revision of nitrogen requirements for optimal yield with pyramided traits. The experiment featured a factorial treatment arrangement in a split-plot randomized complete block design with six nitrogen rates as the main plots and three hybrids differing in corn rootworm traits as the sub-plots. Corn roots were sampled at the beginning of and just after peak larval feeding and run through an Enzyme-linked Immunosorbant Assay (ELISA) to determine gene expression levels. Resulting root injury and adult emergence were measured to assess impacts on larval survival and damage. Root injury generally decreased with nitrogen rate in all hybrids while Bt gene expression, for Cry3Bb1, increased. Nitrogen rate did not affect expression of Cry34 Ab1/Cry35Ab1. Below-ground biomass was found to be highest in the Round-UpTM Ready hybrid at growth stage V6, along with nitrogen uptake. Nitrogen uptake was similar in VT TripleTM to the Round-Up Ready hybrid, which were both significantly higher than the Smart StaxTM hybrid. Yield for the Smart Stax hybrid did not plateau with the nitrogen rates applied at one site in this study, while the unprotected Round-Up Ready hybrid could not take advantage of the higher N rates. Implications of these results for growers in terms of adjusting nitrogen application rates in fields to obtain better gene expression, optimizing hybrid protection from corn rootworm traits, and reducing the risk of resistance are discussed.
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    Effect of nitrogen on Bt gene expression in corn roots, resulting trait performance against corn rootworms (Diabrotica spp.), and transgenic hybrid performance
    (2013-01) Franz, Trisha Marie
    This study examined the impact of nitrogen rates on the expression of corn rootworm (Diabrotica spp.) resistant traits in transgenic corn engineered to express one or more of Bt (Bacillus thuringiensis Berliner) Cry protein(s). The resulting protection against corn rootworm, and the comparative performance of hybrids containing zero, one or multiple (pyramided) corn rootworm traits were evaluated. Recommended nitrogen application rates have been suggested based on economics, but not for optimal expression of Bt Cry proteins. Specifically, this experiment explored the need to shift N rates to optimize Bt trait expression, corn rootworm protection provided by different traits, and a possible revision of nitrogen requirements for optimal yield with pyramided traits. The experiment featured a factorial treatment arrangement in a split-plot randomized complete block design with six nitrogen rates as the main plots and three hybrids differing in corn rootworm traits as the sub-plots. Corn roots were sampled at the beginning of and just after peak larval feeding and run through an Enzyme-linked Immunosorbant Assay (ELISA) to determine gene expression levels. Resulting root injury and adult emergence were measured to assess impacts on larval survival and damage. Root injury generally decreased with nitrogen rate in all hybrids while Bt gene expression, for Cry3Bb1, increased. Nitrogen rate did not affect expression of Cry34 Ab1/Cry35Ab1. Below-ground biomass was found to be highest in the Round-UpTM Ready hybrid at growth stage V6, along with nitrogen uptake. Nitrogen uptake was similar in VT TripleTM to the Round-Up Ready hybrid, which were both significantly higher than the Smart StaxTM hybrid. Yield for the Smart Stax hybrid did not plateau with the nitrogen rates applied at one site in this study, while the unprotected Round-Up Ready hybrid could not take advantage of the higher N rates. Implications of these results for growers in terms of adjusting nitrogen application rates in fields to obtain better gene expression, optimizing hybrid protection from corn rootworm traits, and reducing the risk of resistance are discussed.
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    Extractability of carbon, nitrogen, and phosphorus in United States grasslands
    (2015-02) Thompson, Seth K.
    Tracking how energy flows within and across ecosystems is imperative for understanding interactions among biogeochemical cycles. Aquatic ecosystem metabolism is inextricably linked to the terrestrial landscape, with many lakes getting over 50% of their carbon from terrestrial sources. Nonetheless, there are few large scale measurements of actual carbon export from terrestrial ecosystems. Instead, scientists have relied on a mass balance approach to estimate the quantity of carbon coming into aquatic ecosystems based on estimates of riverine carbon delivery to the ocean. This approach has left many unanswered questions related to the controls on terrestrial organic matter export, both in terms of quantity and quality. Here I used Water Extractable Organic Carbon (WEOC) to estimate potential terrestrial carbon export and to understand the mechanisms controlling these exports. Results from extractions performed at 19 grassland sites across the United States suggested that 1-5% of their total soil carbon was in the water extractable organic carbon pool. In addition, this work suggested that soils selectively retained nitrogen and phosphorus, with less organic nutrient export relative to organic carbon to aquatic ecosystems. These data demonstrated the usefulness of measuring water extractable organic matter (WEOM) on broad spatial scales to gain a better understanding of both the amounts and types of organic matter that are available for export from terrestrial ecosystems.
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    Farmer beliefs and personal norms associated with nitrogen best management practices in the Rush River and Elm Creek Watersheds, Mn
    (2013-05) Olson, Bjorn Anders
    Nitrogen from agricultural nonpoint source pollution is a primary cause of water quality impairments in the Mississippi River Basin. The cumulative effects of nitrogen loading cause water resource problems at local, regional, and national scales as epitomized by the hypoxic "dead zone" at the mouth of the Mississippi River. Agricultural best management practices (BMPs) designed to reduce nitrogen runoff are promoted across the U.S., yet adoption rates are discouragingly low. This study explores farmer perspectives on BMP adoption using interviews with 30 farmers across two agricultural watersheds in southern Minnesota. The research questions that drove this study are 1) What drives nitrogen best management practice adoption among farmers in the study watersheds? 2) What constrains nitrogen best management practice adoption?, and, 3) What role do personal norms play in influencing best management practice decisions? Study findings suggest that three primary drivers (land stewardship, economics, and personal responsibility) motivate BMP adoption; seven primary constraints (including economics, knowledge, and autonomy) hinder adoption; and egoistic, social/altruistic, and biospheric-driven personal norms play varied and influential roles in BMP adoption. An understanding of how drivers, constraints, and personal norms combine to influence farmer decision-making processes is described using the Norm Activation Theory. These drivers, constraints, and the role of personal norms may prove useful when approaching farmers to participate in conservation programs or in tailoring conservation programs to fit farmers' needs.
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    Floating Treatment Wetlands in a Northern Climate: Examination of Phosphorus and Nitrogen Removal
    (2016-05) Deering, Emily
    Excess phosphorus is the largest contributor to nutrient impairment in Minnesota waters. Floating treatment wetlands (FTWs) are a novel best management practice (BMP) to reduce excess nutrients in waterbodies. This study examines the nutrient reduction efficiency of floating treatment wetlands in a northern climate under agricultural loading conditions. A field-based, mesocosm study was completed to quantify the removal efficiency of total phosphorus, Orthophosphate-P, Nitrate-N, and Ammonia-N. The FTWs were each planted with wetland plants Juncus effusus, Eleocharis acicularis, and Glyceria canadensis. A system phosphorus budget was prepared to identify phosphorus sources and sinks within the BMP. Floating treatment wetlands had higher total phosphorus reduction efficiencies. Eleocharis acicularis had the fastest growth rate and highest removal efficiency of the three plants studied. Mesocosms with FTWs had statistically significant lower pH and dissolved oxygen concentrations. Further research areas and FTW design improvements are recommended based on findings from this experiment.
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    Hydrologic flowpath and other natural and anthropogenic factors controlling nitrogen movement from the landscape to streams
    (2015-08) Kronholm, Scott
    The growth of food, fuel, feed, and fiber crops on agricultural land requires additions of nitrogen fertilizer to bolster crop yields. The portion of applied nitrogen that is not utilized by the crops is highly susceptible to transport to nearby streams. Elevated nitrogen concentrations in streams can lead to water quality concerns such as ecosystem degradation or drinking water contamination. Identification of geospatial, environmental, and watershed characteristics (variables) that are correlated with nitrogen concentration in streams will provide a greater understanding of the influence that certain variables have on nitrogen transport to streams. The route through which water travels from the landscape to streams (flowpath) is one of these variables. Movement of many forms of nitrogen is linked to the movement of water, therefore, understanding the fluxes of water to streams will help to expand the understanding of nitrogen transport and the affect that landscape management changes will have on the concentrations of nitrogen in streams. In some areas, groundwater is an important flowpath for delivering water and nitrogen to streams. Hydrograph separation can be used to estimate the amount of total streamflow that is attributable to slowflow sources (flowpaths through which water moves slowly) such as groundwater, and fastflow sources (flowpaths through which water moves quickly) such as overland flow. Because flowpaths have an impact on water and nitrogen transport to streams, testing and improving hydrograph separation techniques is needed. Two independent methods of hydrograph separation, the graphical-based BFI program and chemical tracer-based end-member mixing analysis (EMMA), were used to estimate slowflow contributions to the same streams. The estimates of slowflow from the two separate methods of hydrograph separation were not identical, highlighting the differences in how each method works and the difficulty of accurately estimating slowflow. A modified method of EMMA, referred to as a ratio-based EMMA, was created and tested using synthetic and real stream data. The ratio-based EMMA represents a new method of hydrograph separation, as it produced reasonably accurate slowflow estimates when tested against synthetic and real stream data. The importance of flowpath was then tested in six highly modified streams in agricultural watersheds that had extensive data sets and well understood hydrology. The importance of flowpath on stream nitrogen concentrations in these streams aligned with expectations based on what is currently known. Finally, this study was expanded to a large number of small streams where statistical methods were used to gain broader understanding of the controls on water and nitrogen movement to streams, and to allow for extrapolation of this information to unstudied streams. In addition to flowpath, a small number of geospatial, environmental, and watershed variables were shown to be important for estimating total nitrogen loads and concentrations in a large number of small streams. These variables were used in the development of several multiple linear regression models, many of which performed well when applied to a set of validation streams, having reasonable high R2 values and low normalized root mean squared errors. Determination of the important flowpath(s) as well as other important variables which increase nitrogen movement to streams will allow watershed managers to more accurately implement beneficial land management practices in an effort to reduce nitrogen movement to streams. This knowledge will become increasingly important in an effort to maintain or reduce the amount of nitrogen in streams while increasing crop production to support the rising global population.
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    Improving Maize Production and Ground-Water Quality through Nitrogen Management in Minnesota’s Irrigated Coarse-Textured Soils
    (2016-03) Struffert, Anne
    Elevated groundwater nitrate (NO3-N) concentrations in irrigated sandy soils under corn (Zea mays L.) production in the Midwest is of increasing concern, and has prompted the need to identify new or enhanced nitrogen (N) management practices in these areas. The objective of this study was to evaluate agricultural technologies that may improve N management for profitable corn production and mitigate negative effects of NO3-N in groundwater. From 2011 to 2014 corn was grown at two sites in Minnesota on sandy soils, Dakota County, MN with a continuous corn (CC) rotation and Pope County, MN with a CC, corn after soybeans (CSB), and soybean after corn (SbC) rotations. Twelve treatments were applied including urea broadcast at rates of 0, 45, 90, 135, 180, 225, 270, and 315 kg N ha-1 as a split application, half at pre-plant and half at the V4 development stage, pre-plant Super U at 180 kg N ha-1, and pre-plant ESN at 180 and 225 kg N ha-1. Canopy sensing with SPAD, GreenSeeker, and Crop Circle was done at V8 and V12 and NO3-N basal stalk measurements at R6 development stage. Soil water NO3-N samples were collected weekly throughout the growing season below the rooting zone using suction lysimeters. The mean Maximum Return to N (MRTN) was 231 kg ha-1 and produced a mean-yield increase above the unfertilized check of 6.5 Mg ha-1. Canopy sensors and plant measurements provided limited utility and generally under-predicted N needs. Nitrogen use efficiency and yields were increased with split-applied urea compared to all other pre-plant sources at 180 kg N ha-1, but no reduction in NO3-N leaching occurred. Season-long NO3-N concentrations ranged from 10 to 46 mg L-1 and overall annual loss was 27 to 41 kg NO3-N ha-1. Reducing N rate below the MRTN substantially reduced yield without reducing NO3-N leaching losses.
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    Integrating liquid manure and cover crops to measure their impact on soil health, nutrient cycling, and agronomic performance in the upper Midwest
    (2023-08) Sabbagh, Manuel
    On their own, cover crops and manure have been shown to have a positive impact on various soil biological, chemical, and physical parameters related to soil health. However, there is limited information about the integration of both practices on soil health, nutrient cycling, and agronomic performance of the major crops. This is especially the case for the agronomically important region of the upper Midwest. A two-year study was set up to measure the effects integrating cover crops and liquid-injected manure have on various soil health parameters, nutrient cycling, and corn (Zea mays L.) yield. The study was conducted at the University of Minnesota Southern and West Central Research and Outreach Centers located near Waseca and Morris, MN, respectively. Three agronomic production systems were used: sweet corn-grain corn (System 1); silage corn-silage corn (System 2); and soybean (Glycine max [L.] Merr.)-grain corn (System 3). Plots were laid out in a randomized complete block design with split plots. Nutrient source/timing served as the main plot and cover crop type and planting time/method served as the split plots. Cover crops were drilled after sweet corn harvest in System 1 and were interseeded into standing cash crops or drilled after harvest in Systems 2 and 3. Cover crops were given approximately one month to grow before applying manure. Liquid manure was sweep-injected in the fall when soils were above or below 10°C for Systems 1 and 2 and applied only when soils were at or below 10°C in System 3. Plots without manure were fertilized with urea in the spring (SpringN) with equivalent nitrogen rates to manured plots. To represent typical practices in the region, plots with no cover crop and SpringN application served as the control. Cover crops were sampled for above-ground biomass yield and corn was sampled to measure corn grain or silage yield and their tissue was analyzed for nutrient uptake of macro- and micro-nutrients. Soils were sampled throughout the cover crop and corn growing season to measure soil mineral nitrogen across various soil depths in addition to various soil health indicators. Applying manure when soils were above 10°C in the fall reduced corn grain yield by 0.9 Mg ha-1 compared to SpringN but applying manure when soils were at or below 10°C was as good or better than SpringN in System 1. In System 2, manure, regardless of application time, was more effective than SpringN regarding corn silage yield. Corn grain yield did not differ between manure and SpringN in System 3. However, there is increased risk of losing nitrogen from manure through leaching or other pathways when manure is applied too early as soil mineral nitrogen concentration was similar to plots not yet receiving a nitrogen application in the 0–15-cm soil depth. Therefore, producers are encouraged to follow the University of Minnesota guidelines to apply manure when soils are at or below 10°C in order to minimize nitrogen losses. Furthermore, cover crops had a hard time establishing and producing adequate biomass throughout the study in all systems. Therefore, the integration of cover crops and liquid injected manure did not have an impact (statistically and biologically) on the various soil health indicators measured in the short-term.