Download or read book Effect of Sampling Strategies and Nitrogen Fertilization Best Management Practices on Cumulative Nitrous Oxide Emissions written by Pedro Vitor Ferrari Machado and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis consists of firstly, an assessment of diurnal variation (DV) and effect of sampling frequency on N2O cumulative emissions, and secondly, an evaluation of N2O emissions in response to N fertilization best management practices (BMPs) in a corn field. The first study was performed by sub-sampling a high frequency dataset for growing and non-growing seasons. For growing seasons, taking mid-morning samples twice per week after N fertilization, with an extra sample taken after >10 mm rainfall resulted in lowest uncertainties among the studied strategies. For non-growing seasons mid-morning and mid-afternoon measurements introduced positive errors into the analysis, but taking bi-weekly mid-morning samples still underestimated fluxes due to missing N2O emission events. For the second study, the interaction of soil water content and soil nitrate influenced N2O emissions and the tested BMPs were effective to mitigate N2O emissions when nitrate accumulation was delayed to periods when soil was drier.

Download or read book Effect of mineral N fertilizers N form amount and way of application on nitrous oxide emissions from croplands written by Ulrike Lebender and published by Cuvillier Verlag. This book was released on 2014-07-24 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present work evaluated the effect of mineral nitrogen (N) fertilizer application during crop production on the potential risk of gaseous N loss in the form of nitrous oxide (N2O). Nitrous oxide (N2O) is an environmentally important atmospheric trace gas and contributes to the anthropogenic greenhouse effect. In addition, it is a precursor to photochemical nitric oxide (NO) production in the stratosphere which leads to stratospheric ozone depletion. Agriculture is considered to be the main source of anthropogenic N2O, with agricultural soils representing the single largest source due to nitrogen fertilizer applications during crop production. The purpose of this study was to examine the effects of mineral N fertilizers (N form, amount, mode of application) on N2O emissions from fertilized croplands in north-west Germany. Therefore several field trials, one greenhouse pot experiment and two incubation experiments were conducted. Nitrous oxide fluxes were measured by means of the closed chamber method. The length of the experimental period varied between experiments from several weeks (42 days) up to one-year measurement campaigns. The amount of N2O emitted during the crop growth period depended on the N form applied as well as on the mode of application, and a linear relationship between cumulative N2O emissions and total N fertilizer amount applied was found.

Download or read book Nitrogen in Agricultural Systems written by James Stuart Schepers and published by ASA-CSSA-SSSA. This book was released on 2008 with total page 994 pages. Available in PDF, EPUB and Kindle. Book excerpt: Review of the principles and management implications related to nitrogen in the soil-plant-water system.

Download or read book Nitrous Oxide Emissions in a Landscape Transitioning to the Energy Crops Miscanthus and Switchgrass written by Debasish Saha and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitrous oxide (N2O) emissions from soils are an important component of the greenhouse gas (GHG) balance of agricultural systems. These emissions are particularly relevant when considering the transition of land under the Conservation Reserve Program (CRP) grassland to energy crop, like switchgrass and Miscanthus. The N2O fluxes are in general spatially and temporally variable, which makes field monitoring of this flux challenging. Using the infrequent chamber-based method requires knowledge of spatial and temporal inequality of N2O flux distribution. This dissertation focuses on estimating N2O flux from energy crops aforementioned in a landscape typical of Ridge and Valley region with soil and hydrologic heterogeneity.In chapter 2, I used simulation models and statistical methods to assess the uncertainties of cumulative N2O flux estimates obtained by different temporal sampling frequencies. As a corollary of this work, a robust rule-based sampling framework was designed that provides better estimates of this flux with a lower number of sampling events than the typical fixed-interval sampling methods. The daily soil N2O flux was simulated for Ames, IA; College Station, TX; Fort Collins, CO, and Pullman, WA. A regular sampling of 4- and 8-day interval is required at College Station and Ames, respectively, to yield ±20% accuracy in the flux estimate, while a 12-day interval renders the same accuracy at Fort Collins and Pullman. The uncertainty of the annual N2O flux estimation increased with increasing interval in the fixed interval method, higher in sites with greater flux variability. The rule-based method provided the same accuracy as that of fixed interval with 60% reduction in sampling numbers. The efficiency is higher in sites with greater flux variability.In chapter 3, I examined the effect of land conversion from CRP to energy crops on N2O emissions and how biogeochemical and hydrological factors control the spatial and temporal inequality of N2O flux distribution. The experiment was located in typical Ridge and Valley landscape near the town of Leck Kill, PA. Soil N2O flux, soil mineral nitrogen availability, and profile soil moisture were monitored in shoulder, backslope, and footslope positions under each plot during the growing season of 2013, the second year after land transition. The cumulative N2O flux was significantly (P = 0.009) influenced by vegetation-by-landscape position interaction. Landscape position, nitrate nitrogen, and subsoil soil aeration ([theta]A) were the most important variables to influence soil N2O emissions. The regression tree identified highest N2O emissions occur when [theta]A at 20-40 cm depth is 0.03 m3 m-3, and when there is nitrate in the soil layer. The footslope positions under energy crops were the hot spots of N2O emissions due to prolonged soil saturation and mineral nitrogen availability. The peak emission was triggered by a 100-mm rain event in early June, and contributed 26% of the cumulative flux. Nitrogen fertilization in switchgrass and chisel plowing during Miscanthus establishment caused 48 and 78% higher cumulative flux than the CRP, respectively. The results suggest that land transition only caused significant increase in N2O emissions from the footslope, while the major part of the watershed is at lesser risk of large emissions.The knowledge of hot spots and hot moments of N2O emissions in the landscape is important for its accurate spatial and temporal monitoring, quantification of the emissions, and to minimize the adverse environmental effects of landscape management. A novel application of the concept of inequality (Lorenz curve and Gini coefficients, G) was used to quantify the heterogeneous distribution of N2O in space and time. The G was better correlated (R2 = 0.71, P 0.001, n = 16) with daily N2O emissions than the coefficient of variation and skewness. The hot moment by 100 mm rain event caused highly heterogeneous distribution (G = 0.70) of N2O fluxes in the landscape; however, had little influence on inequality of soil CO2 (G = 0.39) flux distribution among the vegetation types and landscape positions. Overall inequality of N2O flux distribution followed the trend: footslope (G = 0.75) backslope (G = 0.67) shoulder (G = 0.43). Event-based evolution of N2O flux inequality was in accordance with the hydrologic inequality, given the biogeochemical equality prevails in the landscape. The Lorenz curve and G in association with spatial maps are useful tools to guide landscape-scale management strategies to reduce N2O emissions, as well as spatial and temporal monitoring of N2O emissions.Based on the critical threshold of [theta]A

Download or read book Soil Emission of Nitrous Oxide and its Mitigation written by David Ussiri and published by Springer Science & Business Media. This book was released on 2012-11-13 with total page 391 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitrous oxide gas is a long-lived relatively active greenhouse gas (GHG) with an atmospheric lifetime of approximately 120 years, and heat trapping effects about 310 times more powerful than carbon dioxide per molecule basis. It contributes about 6% of observed global warming. Nitrous oxide is not only a potent GHG, but it also plays a significant role in the depletion of stratospheric ozone. This book describes the anthropogenic sources of N2O with major emphasis on agricultural activities. It summarizes an overview of global cycling of N and the role of nitrous oxide on global warming and ozone depletion, and then focus on major source, soil borne nitrous oxide emissions. The spatial-temporal variation of soil nitrous oxide fluxes and underlying biogeochemical processes are described, as well as approaches to quantify fluxes of N2O from soils. Mitigation strategies to reduce the emissions, especially from agricultural soils, and fertilizer nitrogen sources are described in detail in the latter part of the book.

Download or read book The effects of different mineral nitrogen fertilizer forms on N2O emissions from arable soils under aerobic conditions written by Jens Tierling and published by Cuvillier Verlag. This book was released on 2017-05-02 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: Intensively managed agricultural soils are a major source of the greenhouse gas nitrous oxide (N2O), mainly due to the use of mineral nitrogen fertilizers which stimulate microbial processes in soils that form N2O. While oxidized N fertilizer forms can be subject to denitrification, reduced N forms must first be oxidized by nitrification to become available for denitrification. Because the contribution of these processes to N2O emissions depends on the prevailing soil conditions, the choice of the N fertilizer form has the potential to mitigate N2O emissions from fertilized soils. The present study focused on comparing amid-, ammonium- and nitrate-based mineral fertilizers with regard to nitrogen transformation dynamics and N2O production under controlled as well as field conditions. For this two distinct methodological approaches to measure N2O emissions were evaluated and deployed. Furthermore, the effects of soil pH and the alkalizing hydrolysis of urea were investigated. It was shown that especially under aerobic conditions the N fertilizer form can significantly affect N2O production in soils, and that nitrite dynamics are important especially for nitrification-derived N2O emissions. Thus, the careful consideration of the N fertilizer form can be a measure to mitigate emissions from farmland.

Download or read book Impact of Ecologically Based Nutrient Management Strategies on N20 Emissions from Grain Cropping Systems written by Zhen Han and published by . This book was released on 2017 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitrous oxide (N2O) is a potent greenhouse gas and a strong ozone-depletion substance. There is an urgent need to improve management of agricultural nitrogen to reduce N2O emissions from agricultural soils. A vast body of scientific research has investigated the impact of fertilizer-based management strategies, while fewer studies have examined the ecologically-based nutrition management practices (ENM) that manage carbon and nitrogen additions simultaneously and target multiple processes of the nitrogen cycle (e.g. the use of diversified rotations and cover crops). The objective of this work was to better understand the impacts of ENM practices and its interaction with environmental variables on N2O emissions through a meta-analysis, an on-farm experiment, and a 15N tracer experiment. I performed a meta-analysis on 596 pairwise comparisons (129 papers) to compare the efficacy of a wide range of management strategies. ENM practices generally had N2O emissions that were not significantly different from conventional fertilizer-based practices, however this outcome is based on a small number of studies and N was frequently over-applied in the ENM systems. I also conducted an on-farm experiment to assess the interactive effects of landscape characteristics and management regimes. I monitored N2O emissions in two adjacent grain farms in upstate New York that have both undergone the same management for 20 years. I found comparable N2O emissions from winter bare fallow- maize phase in the fertilizer-based field and the legume cover crop (red clover)- maize phase of the cover crop-based rotation. The lowest emissions were found in the winter grain (spelt)- legume cover crop growth period of the organic rotation. The impact of landscape position on N2O emissions was only significant in the fertilizer-based field but not in the cover crop-based field. I conducted a 15N crop residue exchange experiment to measure the contribution of nitrogen from a clover cover crop to N2O emissions. The study found that the dominant source of N2O fluxes shifted from aboveground biomass to belowground sources (root-derived N and soils) around 7 weeks after incorporation. This study provided quantitative evidence that the belowground nitrogen was a significant source of N2O emissions after incorporating legume cover crops. ...

Download or read book Understanding Greenhouse Gas Emissions from Agricultural Management written by Lei Guo and published by OUP USA. This book was released on 2012-04-19 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A valuable source of information for researchers and environmental practitioners, providing the most up-to-date information on greenhouse gas emissions from field crops and livestock animals

Download or read book Carbon and Nitrogen in the Terrestrial Environment written by R. Nieder and published by Springer Science & Business Media. This book was released on 2008-05-30 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon and Nitrogen in the Terrestrial Environment is a comprehensive, interdisciplinary description of C and N fluxes between the atmosphere and the terrestrial biosphere; issues related to C and N management in different ecosystems and their implications for the environment and global climate change; and the approaches to mitigate emission of greenhouse gases. Drawing upon the most up-to-date books, journals, bulletins, reports, symposia proceedings and internet sources documenting interrelationships between different aspects of C and N cycling in the terrestrial environment, Carbon and Nitrogen in the Terrestrial Environment fills the gap left by most of the currently available books on C and N cycling. They either deal with a single element of an ecosystem, or are related to one or a few selected aspects like soil organic matter (SOM) and agricultural or forest management, emission of greenhouse gases, global climate change or modeling of SOM dynamics.

Download or read book Mitigating Gaseous Nitrogen and Carbon Losses From Northeastern Agricultural Soils Via Alternative Soil Management Practices written by Kyle Michael Dittmer and published by . This book was released on 2019 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: Traditional agricultural practices often result in gaseous losses of nitrous oxide (N2O), ammonia (NH3), and carbon dioxide (CO2), representing a net loss of nutrients from agricultural soils, which negatively impacts crop yield and requires farmers to increase nutrient inputs. By adopting best management practices (BMPs; i.e., no-tillage, cover crops, sub-surface manure application, and proper manure application timing), there is great potential to reduce these losses. Because N2O and CO2 are also greenhouse gases (GHGs), climate change mitigation via BMP adoption and emissions reductions would be an important co-benefit. However, adopting a no-tillage and cover cropping system has had setbacks within the Northeast, primarily due to concerns regarding manure nitrogen (N) losses in no-tillage systems as well as uncertainty surrounding the benefits of cover crops. This thesis used two field-trials located in Alburgh, Vermont to assess differences in (i) GHG emissions from agricultural soils, (ii) nitrate and ammonium retention, (iii) corn yield and protein content, and (iv) N uptake and retention via cover crop scavenging under a combination of different BMPs. Chapter 1 evaluates the effects of different reduced-tillage practices and manure application methods (i.e., vertical-tillage, no-tillage, manure injection, and broadcast manure application) on reducing N2O and CO2 emissions, retaining inorganic N, and improving crop yields. Greenhouse gas measurements were collected every other week for the growing season of 2015-2017 via static chamber method using a photoacoustic gas analyzer. Results from this study showed that tillage regimes and manure application method did not interact to affect any of the three research objectives, although differences between individual BMPs were observed. Notably, vertical tillage enhanced CO2 emissions relative to no-tillage, demonstrating the role of soil disturbance and aeration on aerobic microbial C transformations. Manure injection was found to significantly enhance both N2O and CO2 emission relative to broadcast application, likely due to the formation of anerobic micro-zones created from liquid manure injection. However, plots that received manure injection retained greater concentrations of soil nitrate, a vital nutrient for quality crop production, thereby highlighting a major tradeoff between gaseous N losses and N retention with manure injection. Chapter 2 evaluates the effects of tillage practices and timing of manure application to increase N retention with the use of cover crops in order to mitigate GHG emissions, enhance soil nitrate and ammonium retention, and improve cropping system N uptake. Treatments at this field trial consisted of a combination of the presence or absence of cover crops, no-tillage or conventional-tillage, and spring or fall manure application. Greenhouse gas emissions were measured every other week via static chamber method using a gas chromatograph for the growing season of 2018. Results from this study showed that the presence of cover crops enhanced both N2O and CO2 emissions relative to fallow land, irrespective of tillage regime and manure application season, likely as a result of greater N and carbon substrates entering the soil upon cover crop decomposition. Due to enhanced N2O emissions with cover crops, cover crops did not retain significantly greater inorganic N in the system upon termination.

Download or read book The Emissions of Nitrous Oxide from Agricultural Fields in New York State written by Marina Molodovskaya and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The atmospheric nitrous oxide (N2O) is of special interest, due to its persistent effect as a potent greenhouse gas and stratospheric ozone destructor. Animal manure fertilization is one of the key factors contributing to N2O formation. In the Northeastern US, dairy industry is the largest agricultural activity, and the manure cropland fertilization is a common practice. Continuous monitoring of N2O emissions from croplands in New York State was conducted by eddy covariance method from 2006 to 2009. The research was aimed at quantification of N2O emissions from manure-fertilized corn (Zea mays) and alfalfa (Medicago sativa) fields, estimating strength and spatial variability of soil N2O sources by conducting simultaneous static chamber campaign, and analysis of temporal distribution of N2O fluxes as affected by seasonality of climate variations and manure practices. The analysis of cumulative N2O emissions and source contributions into the integrated flux showed that manure nitrogen (N) was the most important factor controlling the extent of N2O formation: areas which received more manure N were stronger N2O emitters. Whereas N availability determined a magnitude of N2O emissions, the environmental changes altering soil moisture and temperature status were major N2O event triggers. The temporal flux distribution demonstrated episodic event-induced nature of N2O peak fluxes, which were primarily driven by strong rainfall and warm temperatures in growing season and soil thaw in winter and early spring. The greatest N2O emissions were observed when flux-triggering weather events coincided with or followed manure application. The most intense single N2O peak event was produced from combination of summer manure spreading and strong rainfall; however spring thaw-induced N2O fluxes showed more consistent seasonal year-to-year trend. The daily average fluxes measured by the EC and chamber techniques were in good agreement. The spatial variability of chamber measurements was mainly caused by high heterogeneity of soil N2O formation, which resulted both in net N2O production and consumption. The EC integrated flux was strongly dependent on wind direction and contributing footprint. The combination of the two different scale methods may help in reducing temporal and spatial variability of N2O estimates and improving N2O emission data quality. .

Download or read book Nitrous Oxide Emissions from California Tomato Cropping Systems Under Conventional and Alternative Management written by Taryn Lee Kennedy and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Primarily associated with soil fertility management practices, nitrous oxide (N2O) is a potent greenhouse gas (GHG) whose emission from farmland is a concern for environmental quality and agricultural productivity. In California, agriculture and forestry account for 8% of the total GHG emissions, of which 50% is accounted for by N2O (CEC, 2005). Furrow irrigation and high temperatures in the Central Valley, together with conventional fertilization, are ideal for the production of food, but also N2O production. These conditions can promote N2O emissions, but also suggest great potential to reduce N2O emissions by optimizing fertilizer and irrigation management. Smaller, more frequent fertilizer applications increase the synchrony between available soil nitrogen (N) and crop N uptake and may result in less N loss to the atmosphere. Given that the ecosystem processes regulating the production of N2O respond to and interact with multiple factors influenced by environmental and managerial conditions, it is not always feasible to approach the study of integrated agricultural systems and their affect on GHG emissions by use of a factorial experiment alone. On-farm studies are therefore an important precursor to research station trials to determine which management practices and components of a complete management system should be targeted and isolated for future study. Farm-based trials also provide a realistic evaluation of current management practices subject to practical and economic constraints. The following study took place on existing farms in order to assess the effect of active, operational farm field conditions and current managements on GHG emissions and to thoroughly characterize two typical management systems. In this study, I determined how management practices, such as fertilization, irrigation, tillage, and harvest, affect direct N2O emissions in tomato cropping systems under two contrasting irrigation managements and their associated fertilizer application method, i.e. furrow irrigation and knife injection (conventional system) versus drip irrigation, reduced tillage, and fertigation (integrated system). Field sites were located on two farms in close proximity, on the same soil type, and were planted with the same crop cultivar. This project demonstrated that shifts in fertilizer and irrigation water management directly affect GHG emissions. More fertilizer was applied in the conventional system (237 kg N ha−1 growing season−1) than the integrated system (205 kg N ha−1 growing season−1). The amount of irrigated water was comparable between the two systems; 64 to 70 cm was applied in the conventional system and 64 cm in the integrated system. Total weighted growing season emissions were 3.4 times greater in the conventional system (2.39 ± 0.17 kg N2O-N ha−1) than the integrated system (0.58 ± 0.06 kg N2O-N ha−1), with a higher tomato yield in the integrated system (131 vs. 86 Mg ha−1). The highest conventional N2O emissions resulted from fertilization plus irrigation events and the first fall precipitation. In the integrated system, the highest N2O fluxes occurred following harvest and the first fall precipitation. Environmental parameters of soil moisture, soil mineral N, and dissolved organic carbon (DOC) were higher and more spatially variable in the conventional system. Reduced N2O emissions in the integrated system, resulting from low soil moisture, mineral N concentrations, and DOC levels, imply that improved fertilizer and water management strategies can be effective in mitigating greenhouse gas emissions from agriculture.

Download or read book Nitrous Oxide Emissions from Variable Rate Application of Nitrogen Fertilizer to Panicum Virgatum L in Qu bec Canada written by Alexia Bertholon and published by . This book was released on 2022 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "Nitrogen (N) fertilizer is essential to maintain agricultural yields but is susceptible to reactions that produce nitrous oxide (N2O), which acts as a greenhouse gas and contributes to stratospheric ozone depletion. It is difficult to predict where these reactions will produce 'hot spots' of high N2O fluxes in a field, as well as the 'hot moments' when peak N2O fluxes occur. The objective of this study is to relate the N2O fluxes in a Panicum virgatum L. (switchgrass) field to N fertilizer application rates of 0, 50, 100, and 150 kg N ha-1 while considering the spatial-temporal heterogeneity of the field. In summer 2017, soil samples were collected at 128 locations in an 8.87 ha switchgrass field in the Cookshire-Eaton region (45°20'N, 71°46'W) of Québec, Canada. The sandy loam soil was analysed for standard soil test parameters: macro- and micro-nutrient content, pH and texture. In addition, proximal soil sensing was done to characterize the elevation, electrical conductivity and surface spectral reflectance. This data was used to generate a spatial soil map of the field with R 3.4.1 statistical software and ArcGIS, which revealed three distinct management zones in the field. In spring 2018, four N fertilizer rates were applied to blocks (15 m wide x 100 m long), which created four blocks with variable N fertilizer rates in the high-yielding switchgrass zone and four blocks with variable N fertilizer rates in the low-yielding switchgrass zone. Non-flow-through non-steady-state chambers were installed (n=3 per block) for manual gas sampling and N2O fluxes were calculated during a 1 h period every 7-10 d during the growing season. The experiment was repeated in spring 2019 in the same management zones but in newly-selected blocks that had uniform fertilization in the 2018 growing season. Four N fertilizer rates were applied at random to 4 blocks in the high-yielding zone, plus 4 blocks in the low-yielding zone, and gas sampling chambers (n=3) were placed in new locations in each block. The "hot moments" of N2O flux occurred in the first 30 d after N fertilizer application. Although N2O fluxes differed in the management zones in 2018, there were no distinctive "hot spots" in the switchgrass field in the 2019 growing season. However, the cumulative N2O emission in each growing season tended to increase with greater N fertilizer rates, suggesting that applying more N fertilizer increased the risk of gaseous N loss, probably through denitrification. I conclude that precision agriculture techniques based on geospatial characterization of agricultural fields may help to calibrate site-specific N fertilizer inputs and meet agroenvironmental goals by improving crop production while reducing N2O emissions"--

Download or read book Atmospheric Boundary Layer Flows written by J. C. Kaimal and published by Oxford University Press, USA. This book was released on 1994 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text gives a simple view of the structure of the boundary layer, the instruments available for measuring its mean and turbulent properties, how best to make the measurements, and ways to process and analyze the data.

Download or read book Methods of Introducing System Models into Agricultural Research written by Lajpat R. Ahuja and published by John Wiley & Sons. This book was released on 2020-01-22 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: Why model? Agricultural system models enhance and extend field research...to synthesize and examine experiment data and advance our knowledge faster, to extend current research in time to predict best management systems, and to prepare for climate-change effects on agriculture. The relevance of such models depends on their implementation. Methods of Introducing System Models into Agricultural Research is the ultimate handbook for field scientists and other model users in the proper methods of model use. Readers will learn parameter estimation, calibration, validation, and extension of experimental results to other weather conditions, soils, and climates. The proper methods are the key to realizing the great potential benefits of modeling an agricultural system. Experts cover the major models, with the synthesis of knowledge that is the hallmark of the Advances in Agricultural Systems Modeling series.

Download or read book Toward Understanding the Impact of Management Practices on Soil Microbial Nitrogen Dynamics in Agroecosystems written by Mara Cloutier and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Emissions were affected by termination timing x day of sampling (DOY) and residue treatment x DOY, but no strong patterns were observed. Cumulative N2O emissions were highly correlated with aboveground residue C and C/N and root C/N. Daylight hours and corn growing degree days were significant predictors of N2O emissions. Interactions between soil temperature, NH4+, and corn growing degree days only explained ~ 10% of the variation in N2O emissions. Assessment of complete denitrification or 15N tracing experiments should be explored in the context of perennial termination to identify strategies to limit N2O emissions. In Chapter 6 I used a novel approach to integrate soil health and soil metagenomes to assess differences in soil health and microbial N metabolisms between uncultivated soils and cropped soils managed with contrasting practices. Soil samples were collected from dairy farms and included samples from forest or hedgerows next to cropping soils managed with either no-till and conventional amendments or tillage and organic amendments. Soil health was assessed using chemical, physical, and biological indicators using two sets of soil health tests. Soil microbially-mediated N transformations were quantified through whole-shotgun metagenomics. Soil health, particularly related to organic C and N, were highest in uncultivated soils followed by cropped soils from no-till farms while cropped soils from tilled-organic farms had the poorest soil health. Microbial genes for organic N use were correlated with soil quality indices and were highest in uncultivated soils, while inorganic N use genes were negatively correlated with ACE protein and were highest in the cropped soils. Dairy farm soil management employing no-till increased soil health and microbial organic N metabolisms relative to tilled-organic soils. Organic N metabolisms like urea production and consumption may be appropriate biological indicators of soil health. Further exploration across a wider range of cropping systems would be necessary to fully assess the validity in urea cycling in delineating soil health.

Download or read book Nitrous Oxide Emissions written by Miguel Andres Arango Argoti and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nitrogen is critical for plant growth and is a major cost of inputs in production agriculture. Too much nitrogen (N) is also an environmental concern. Agricultural soils account for 85% of anthropogenic N2O which is a major greenhouse gas. Management strategies for N fertilization and tillage are necessary for enhancing N use efficiency and reducing negative impacts of N to the environment. The different management practices induce changes in substrate availability for microbial activity that may result in increasing or reducing net N2O emitted from soils. The objectives of this research were to (1) integrate results from field studies to evaluate the effect of different management strategies on N2O emissions using a meta-analysis, (2) quantify N2O-N emissions under no-tillage (NT) and tilled (T) agricultural systems and the effect of different N source and placements, (3) perform sensitivity analysis, calibration and validation of the Denitrification Decomposition (DNDC) model for N2O emissions, and (4) analyze future scenarios of precipitation and temperature to evaluate the potential effects of climate change on N2O emissions from agro-ecosystems in Kansas. Based on the meta-analysis there was no significant effect of broadcast and banded N placement. Synthetic N fertilizer usually had higher N2O emission than organic N fertilizer. Crops with high N inputs as well as clay soils had higher N2O fluxes. No-till and conventional till did not have significant differences regarding N2O emissions. In the field study, N2O-N emissions were not significantly different between tillage systems and N source. The banded N application generally had higher emissions than broadcasted N. Slow release N fertilizer as well as split N applications reduced N2O flux without affecting yield. Simulations of N2O emissions were more sensitive to changes in soil parameters such as pH, soil organic carbon (SOC), field capacity (FIELD) and bulk density (BD), with pH and SOC as the most sensitive parameters. The N2O simulations performed using Denitrification Decomposition model on till (Urea) had higher model efficiency followed by no-till (compost), no-till (urea) and till (compost). At the regional level, changes in climate (precipitation and temperature) increased N2O emission from agricultural soils in Kansas. The conversion from T to NT reduced N2O emissions in crops under present conditions as well as under future climatic conditions.