Assessment of Baseline Nitrous Oxide Emissions in California Cropping Systems PDF Download

Author: William R. Horwath
Publisher:
ISBN:
Category : Atmospheric nitrous oxide
Languages : en
Pages : 96

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Author: Martin Burger
Publisher:
ISBN:
Category : Cropping systems
Languages : en
Pages : 62

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Book Description

Author: William R. Horwath
Publisher:
ISBN:
Category : Atmospheric nitrous oxide
Languages : en
Pages : 50

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"Nitrogen inputs, crop N removal, and cumulative N2O emissions were measured from spring 2011 to fall 2012 in three dairy forage production systems receiving liquid and solid manure, as well as synthetic N fertilizer"--Page vii.

Author: Martin Burger
Publisher:
ISBN:
Category : Cropping systems
Languages : en
Pages : 104

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Author: Thomas P. Tomich
Publisher: Univ of California Press
ISBN: 0520962230
Category : Science
Languages : en
Pages : 341

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Book Description
Nitrogen is indispensable to all life on Earth. However, humans now dominate the nitrogen cycle, and nitrogen emissions from human activity have real costs: water and air pollution, climate change, and detrimental effects on human health, biodiversity, and natural habitats. Too little nitrogen limits ecosystem processes, while too much nitrogen transforms ecosystems profoundly. The California Nitrogen Assessment is the first comprehensive account of nitrogen flows, practices, and policies for California, encompassing all nitrogen flows—not just those associated with agriculture—and their impacts on ecosystem services and human wellbeing. How California handles nitrogen issues will be of interest nationally and internationally, and the goal of the assessment is to link science with action and to produce information that affects both future policy and solutions for addressing nitrogen pollution. This book also provides a model for application of integrated ecosystem assessment methods at regional and state (subnational) levels.

Author: Thomas P. Tomich
Publisher: Univ of California Press
ISBN: 0520287126
Category : Nature
Languages : en
Pages : 340

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"Collaborating Institutions: Agricultural Sustainability Institute at UC Davis, UC ANR Sustainable Agriculture Research and Education Program, UC ANR Kearney Foundation of Soil Science, UC ANR Agricultural Issues Center, UC ANR California Institute for Water Resources, Water Science and Policy Center at UC Riverside."

Author: Charlotte Decock
Publisher:
ISBN: 9781267398338
Category :
Languages : en
Pages :

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Agricultural soils encompass one of the major sources of anthropogenic nitrous oxide (N2O), a potent greenhouse gas and stratospheric ozone depleting substance. Therefore, accurate prediction of N2O emissions from soils and development of effective mitigation strategies are pertinent. However, the scientific understanding of mechanisms underlying N2O emissions is limited, in part, by the lack of suitable methods to assess sources of N2O, especially under field conditions and in undisturbed soil cores. In this dissertation, two ecological applications of source-partitioning N2O were considered: (1) the feedback of N2O emissions to elevated atmospheric CO2 and tropospheric O3 and (2) mechanisms underlying N2O emissions during a simulated rainfall event in a tomato cropping system in California. Furthermore, four methods were evaluated for their utility in source-partitioning N2O with minimal disturbance of the system: (1) tracing of added 15N enriched NH4 and/or NO3− to N2O, (2) use of natural abundance 15N of N2O and its precursors, (3) measuring the intramolecular distribution of 15N in N2O, expressed as site preference (SP), and (4) determining relationships between natural abundance 18O and 15N. Method comparisons elucidated that the use of isotope models that include all natural abundance isotopes of N2O and its precursors and uncertainty deductions for isotope fractionation factors to estimate N transformation rates and sources of N2O during peak N2O emissions is the most promising approach to improve our understanding of mechanisms underlying N2O emissions with minimal sampling-associated disturbance of the system. Various approaches to study sources of N2O and N-cycling suggested that elevated CO2 and O3 will unlikely cause a feedback on global climate change through altered N2O emissions in soybean agroecosystems in the Midwestern USA. Furthermore, elevated CO2 decelerated, whereas elevated O3 accelerated N-cycling if integrated over longer time scales. In a California tomato cropping system, N2O reduction to N2 decreased progressively as soil dried out following wetting up. Overall, this dissertation illustrates the added benefit of studying mechanisms underlying N2O emissions in addition to field N2O fluxes per se and encourages further research to source-partition N2O emissions and its needed methodology to understand N2O responses of agroecosystems in a changing global environment.

Author: Maria Ponce De Leon Jara
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
Crop rotations, organic nutrient amendments, reduced tillage practices, and integration of cover crops are practices that have the potential to increase the sustainability of crop production, yet they also impact nitrous oxide (N2O) emissions. Agricultural soil management has been estimated to contribute 79% of the total N2O emissions in the U.S., and inorganic nitrogen (N) fertilization is one of the main contributors. Nitrous oxide is a potent greenhouse gas that has a global warming potential which is approximately 298 times that of carbon dioxide (CO2) over a 100-year period and is currently the dominant ozone-depleting substance. Few studies have assessed the effects of organic N amendments on direct N2O within the context of a typical dairy forage cropping system. Most research has been limited to studying the effects of one or two sources of N inputs on N2O emissions; however, dairy forage cropping systems often apply manure and have more than two N sources that likely both contribute to N2O emissions. This study investigated how different dairy cropping practices that include differences in crop residues, N inputs (dairy manure and inorganic fertilizer), timing of N amendment applications and environmental conditions influenced N2O emissions from no-till soil planted to corn (Zea mays L.). A two-year field study was carried out as part of the Pennsylvania State Sustainable Dairy Cropping Systems Experiment, where corn was planted following annual grain crops, perennial forages, and a green manure legume crop; all were amended with dairy manure. In the corn-soybean (Glycine max (L.) Merr.) rotation, N sources (dairy manure and inorganic fertilizer) and two methods of manure application (broadcasted and injected) were also compared.Chapter 1 reviews the scientific literature; describing the biotic and abiotic processes of N2O production in soils, summarizing current research on N2O emissions in agricultural systems, and emphasizing the main management and environmental drivers contributing to the emissions. This chapter reviews methods for matching N supply with crop demand, coupling N flow cycles, using advanced fertilizer techniques, and optimizing tillage management. Also, the applicability and limitations of current research to effectively reduce N2O emissions in a variety of regions are discussed.Chapter 2 analyzes the effect of corn production management practices and environmental conditions contributing to N2O in the Pennsylvania State Sustainable Dairy Cropping Systems Experiment. Significantly higher N2O emissions were observed 15-42 days after manure injection and 1-4 days after mid-season UAN application. Manure injection had 2-3 times greater potential for N2O emissions compared to broadcast manure during this time period. Integration of legumes and grasses in the cropping system reduced inorganic fertilizer use compared to soybean with manure or UAN, however, direct N2O emissions were not reduced. The Random Forest method was used to identify and rank the predictor variables for N2O emissions. The most important variables driving N2O emissions were: time after manure application, time after previous crop termination, soil nitrate, and moisture. These field research results support earlier recommendations for reducing N losses including timing N inputs close to crop uptake, and avoiding N applications when there is a high chance of precipitation to reduce nitrate accumulation in the soil and potential N losses from denitrification.Chapter 3 reports the comparison of N2O fluxes predicted with the biogeochemical model DAYCENT compared to measured data from the two-year dairy cropping systems study. Daily N2O emissions simulated by DAYCENT had between 41% and 76% agreement with measured daily N2O emissions in 2015 and 2016. DAYCENT overestimated the residual inorganic N fertilizer impact on N2O emissions in the corn following soybean with inorganic fertilizer and broadcast manure. Comparisons between DAYCENT simulated and measured N2O fluxes indicate that DAYCENT did not represent well organic N amendments from crop residues of perennials and legume cover crops, or manure application in no-till dairy systems. DAYCENT was generally able to reproduce temporal patterns of soil temperature, but volumetric soil water contents (VSWC) predicted by DAYCENT were generally lower than measured values. After precipitation events, DAYCENT predicted that VSWC tended to rapidly decrease and drain to deeper layers. Both the simulated and measured soil inorganic N increased with N fertilizer addition; however, the model tended to underestimate soil inorganic N concentration in the 0-5 cm layer. Our results suggest that DAYCENT overestimated the residual N impact of inorganic fertilizer on N2O emissions and mineralization of organic residues and nitrification happened faster than DAYCENT predicted. Chapter 4 highlights the impact of manure injection and the importance of timing organic N amendments from manures and/or crop residue with crop N uptake to mitigate N2O emissions. More research is needed to better understand the tradeoffs of these strategies in no till dairy cropping systems to help farmers in their operational management decisions. Improving the parametrization of DAYCENT for dairy cropping systems in no-till systems with high surface legume crop residues from perennials and cover crops, will make the model a more useful tool for testing different mitigation scenarios for farmers and policy-designer decision making.

Author: Changsheng Li
Publisher:
ISBN:
Category : Atmospheric nitrous oxide
Languages : en
Pages : 76

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Author: Jonathan Vick
Publisher:
ISBN: 9781369795554
Category :
Languages : en
Pages :

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Nitrous oxide (N2O) is a potent greenhouse gas (GHG) with a global warming potential (GWP) 298 times greater than CO2. Cover crops, those crops grown other than the cash crop, offer a range of benefits for growers. However, cover crops also serve as inputs of carbon (C) and nitrogen (N), that can stimulate microbial N2O emissions. Vineyard agroecosystems represent a unique case for studying the effects of cover crops on N2O emissions as vineyard cover crops are generally non-fertilized and rain-fed. A two-year field study and accompanying laboratory incubation was conducted to examine the effects of three cover crop treatments (a legume mix, a ‘soil builder’ mix, and perennial ryegrass) and a fallow control on soil GHG emissions and soil N-dynamics. N2O emissions over the course of the study period did not show significant differences, with emissions ranging from 550 ± 202 g N2O-N ha−1 from the fallow soil to 951 ± 135 g N2O-N ha−1 from the ryegrass planted soil. Precipitation patterns were an important driver of N2O emissions. The laboratory incubation results showed N2O emissions from the legume mix planted soil to be an order of magnitude higher than the other treatments, with denitrification as the pathway responsible for the observed differences in gaseous N production rates. Additionally, patterns of N-transformations exhibited treatment differences, suggesting that two years of cover cropping influenced soil microbial community behavior.