Browsing by Subject "Carbon footprint"

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Effects of nitrification inhibitors and application technique on trace gas fluxes from a maize field after cattle slurry fertilization
(2019) Herr, Christina; Müller, Torsten
In a time of climate change and against the background of intensive animal husbandry and biogas production in Germany, strategies for mitigation of greenhouse gas (GHG) release and Nitrogen (N) losses from silage maize production become increasingly important, especially for organic fertilizers. Consequently, the main objective of this study was to determine the height of GHG release from silage maize production on a medium textured soil which is typical for this region in Southwest Germany and to evaluate useful fertilization opportunities to mitigate carbon dioxide (CO2) footprint per yield unit. To identify management factors improving GHG budget from silage maize, annual nitrous oxide (N2O) and methane (CH4) measurements were carried out during maize growth and subsequent black fallow at least weekly. Investigations were conducted over two years on two adjacent fields (one for each study year). Amounts of ammonia (NH3) volatilizations after fertilization and nitrate (NO3-) leaching losses were also included in GHG balances. In dependence on available data, determined or estimated values were used. Additionally, yield and N removal from maize plants were quantified. The basic treatments of this study which investigated impact of fertilizer form and application techniques, were an unfertilized control (CON), a mineral fertilization (MIN), a banded cattle slurry application by trailing hose and subsequent incorporation (INC) and a cattle slurry injection (INJ). As confirmed repeatedly, in contrast to broadcast slurry incorporation, slurry injection efficiently reduced the risk of NH3 losses by direct slurry placement into the soil, but simultaneously provoked N2O formation more strongly, probably due to the anaerobic conditions in the injection slot favoring denitrification. For reducing N2O release from slurry injection, the applicability of six single or combined nitrification inhibitors (NIs) concerning potential GHG reduction were investigated. This N2O reduction should be reached through the desynchronized availability of carbon (C) and NO3-, derived from nitrified slurry ammonium (NH4+). Thus, in the period after slurry application, N2O losses from denitrification as well as from nitrification should be reduced through NIs. For final evaluation, collection of measured and estimated data (including direct and indirect N2O losses (NH3, NO3-), CH4 budget, pre-chain emissions from mineral fertilizer and fuel consumption) were converted into CO2 equivalents and summarized as area- or yield-related GHG balances. Except for one of the INJ treatments with NI (exclusively investigated in the first year) and one INC treatment with NI (exclusively investigated in the second year), all remaining treatments were tested in both experimental years. The height of NH3 emissions from INC treatment (12-23 % of applied NH4+-N) was more weather-dependent than those from INJ treatment (12-15 % of applied NH4+-N). In mean over both years, cumulative N2O emission from INJ treatment (13.8 kg N2O-N ha-1 yr-1), was significantly higher than from CON, MIN, and INC which recorded 2.8, 4.7, and 4.4 kg N2O-N ha-1 yr-1. NIs decreased the fertilization-induced N2O emissions from injection by 36 % (mean over all NIs and years) by an order of magnitude comparable to slurry incorporation. The NIs investigated tended to be categorized in inhibitors with prior and delayed inhibitory maximum. Whether low persistence, or poor biological degradability was an advantage, depended on environmental conditions. A combination of two NIs, one with putative prior and one with delayed release behavior reached the highest N2O reduction. In the additional INC treatment, this NI combination tended to reduce annual N2O release by 20 % in comparison to incorporation without inhibitor. Beside the potential of reducing fertilization-induced N2O emissions, NIs might also help to improve CH4 budgets in silage maize production. In general, CON, MIN and INC were net CH4 sinks in both years with mean uptakes of 460, 127, and 793 g CH4-C ha-1 yr-1, respectively. Conversely, slurry injection resulted in net CH4 emissions of 3144 g CH4-C ha-1 yr-1 (mean over both years). However, NIs tended to reduce CH4 emissions from injection by around 48 % and increased CH4 consumption from slurry incorporation by 20 %. Across all treatments and years, direct N2O emissions were the major contributor to total GHG balance. Yield-related GHG budgets from both years were lowest for CON, followed by INC or MIN treatment and significantly highest for sole slurry injection. NIs decreased fertilization-induced GHG release from injection in mean over both years by order of magnitude comparable with slurry incorporation. Consequently, alongside slurry incorporation and broadcast mineral fertilization, slurry injection combined with recommended NIs was evaluated as an equally appropriate fertilization strategy in terms of the atmospheric burden for livestock farmers.
Environmental and economic assessment of the intensive wheat - maize production system in the North China Plain
(2016) Ha, Nan; Bahrs, Enno
To ensure food security for its vast population input intensification in crop production has been one of China’s major strategies in the last decades. However, the negative environmental impact of the highly intensive crop production becomes apparent. Especially the emission of greenhouse gases (GHG) constitutes a major sustainability issue of crop production in China. The winter wheat - summer maize (WW-SM) double cropping system plays a crucial role for China’s national food security. Strong research efforts mainly focusing on field experiments insufficiently consider the economic viability of the proposed improvement strategies and farmers’actual crop management. Therefore this study aims to fill this void by assessing farmers’actual crop management in the WW-SM production system, with regard to its environmental and economic performance to derive suitable improvement strategies for more sustainable crop production in the North China Plain (NCP). This cumulative PhD thesis consists of three papers published or accepted with revisions in international peer-reviewed journals. A field survey conducted in 2011 interviewing 65 WW-SM producing farm households constitutes the core data base for the thesis’analysis. The data was supplemented by expert interviews and specific secondary data. Partial life cycle analysis and economic assessment were conducted, comprising GHG emission, product carbon footprint (PCF), gross margin (GM), variable cost per unit product and life cycle costing (LCC) as key environmental and economic indicators, respectively. The first article describes the status quo of single farm environmental and economic performance of 65 WW-SM producers. The results revealed a huge heterogeneity among farms. Astonishingly no trade-off between productivity and sustainability could be identified in the region. Building on cluster analysis, with farms grouped according to their economic and environmental performance into “poor”, “fair” and “good” producers, the regional GHG mitigation potential was estimated. Under the scenario assumption that all grain in the NCP is produced under “good” production conditions, 21% and 7% of GHG could be mitigated in wheat and maize production, respectively. To be able to address the existing heterogeneity and develop strategies towards attaining GHG mitigation in practice, the second article aimed at assessing the factors determining farmers’ current environmental and economic performance. Using stepwise multiple linear regression (SMLR) it was revealed that nitrogen (N) input and electricity for irrigation were responsible for 0.787 and 0.802 of variability (adjusted R2) in the GHG emission results of the WW and SM production, respectively. Electricity for irrigation and labor were the most significant factors explaining the differences in LCC of WW and SM production, with an adjusted coefficient of determination (adjusted R2) of 0.397 and 0.29. This finding indicates that N input, electricity for irrigation and labor are key target areas for lowering GHG emissions and production costs of the WW-SM production system in the NCP. As revealed in the second article overuse of N fertilizer, which actually constitutes a major current issue in China, offers great potential for reducing GHG emissions and production costs in the WW-SM production system. Therefore in the third article three simple and easily to apply N fertilizer recommendation strategies are tested, which could be implemented on large scale through the existing agricultural advisory system of China, at comparatively low cost. Building on the household dataset, the effects of the three N strategies under constant and changing yield levels on PCF and GM were determined for every individual farm household. The N fixed rate strategy realized the highest improvement potential in PCF and GM in WW; while the N coefficient strategy performed best in SM. The analysis furthermore revealed that improved N management has a significant positive effect on PCF, but only a marginal and insignificant effect on GM. On the other side, a potential 10 % yield loss would have only a marginal effect on PCF, but a detrimental effect on farmers’income. It will be of vital importance to avoid any yield reductions and respective severe financial losses, when promoting and implementing advanced fertilization strategies. Therefore, it is furthermore recommended to increase the price of fertilizer, improve the agricultural extensions system, and recognize farmers’ fertilizer related decision-making processes as key research areas. The presented thesis gives valuable contributions to the development of environmentally and economically more sustainable crop production systems in the NCP. The thesis concludes that an adjustment in the agricultural advisory system is required, supported by more interdisciplinary research, which is able to address the inherent complexity of realizing more sustainable crop production in China.
Varietal effects on methane intensity of paddy fields under different irrigation management
(2023) Vo, Thi Bach Thuong; Johnson, Kristian; Wassmann, Reiner; Sander, Bjoern Ole; Asch, Folkard
Alternate wetting and drying irrigation (AWD) has been shown to decrease water use and trace gas emissions from paddy fields. Whereas genotypic water use shows little variation, it has been shown that rice varieties differ in the magnitude of their methane emissions. Management and variety‐related emission factors have been proposed for modelling the impact of paddy production on climate change; however, the magnitude of a potential reduction in greenhouse gas emissions by changing varieties has not yet been fully assessed. AWD has been shown to affect genotypic yields and high‐yielding varieties suffer the greatest loss when grown under AWD. The highest yielding varieties may not have the highest methane emissions; thus, a potential yield loss could be compensated by a larger reduction in methane emissions. However, AWD can only be implemented under full control of irrigation water, leaving the rainy seasons with little scope to reduce methane emissions from paddy fields. Employing low‐emitting varieties during the rainy season may be an option to reduce methane emissions but may compromise farmers’ income if such varieties perform less well than the current standard. Methane emissions and rice yields were determined in field trials over two consecutive winter/spring seasons with continuously flooded and AWD irrigation treatments for 20 lowland rice varieties in the Mekong Delta of Vietnam. Based on the results, this paper investigates the magnitude of methane savings through varietal choice for both AWD and continuous flooding in relation to genotypic yields and explores potential options for compensating farmers’ mitigation efforts.