Rice husk biochar and crop residue amendment in subtropical cropping soils: Effect on biomass production, nitrogen use efficiency and greenhouse gas emissions

We investigated the effect of maize residues and rice husk biochar on biomass production, fertiliser nitrogen recovery (FNR) and nitrous oxide (N2O) emissions for three different subtropical cropping soils. Maize residues at two rates (0 and 10 t ha−1) combined with three rates (0, 15 and 30 t ha-1) of rice husk biochar were added to three soil types in a pot trial with maize plants. Soil N2O emissions were monitored with static chambers for 91 days. Isotopic 15N-labelled urea was applied to the treatments without added crop residues to measure the FNR. Crop residue incorporation significantly reduced N uptake in all treatments but did not affect overall FNR. Rice husk biochar amendment had no effect on plant growth and N uptake but significantly reduced N2O and carbon dioxide (CO2) emissions in two of the three soils. The incorporation of crop residues had a contrasting effect on soil N2O emissions depending on the mineral N status of the soil. The study shows that effects of crop residues depend on soil properties at the time of application. Adding crop residues with a high C/N ratio to soil can immobilise N in the soil profile and hence reduce N uptake and/or total biomass production. Crop residue incorporation can either stimulate or reduce N2O emissions depending on the mineral N content of the soil. Crop residues pyrolysed to biochar can potentially stabilise native soil C (negative priming) and reduce N2O emissions from cropping soils thus providing climate change mitigation potential beyond the biochar C storage in soils. Incorporation of crop residues as an approach to recycle organic materials and reduce synthetic N fertiliser use in agricultural production requires a thorough evaluation, both in terms of biomass production and greenhouse gas emissions.

Experimental investigation of the effects of oxygenated fuels on exhaust emissions in a heavy duty diesel engine

Physical and chemical properties of biofuels vary among various feedstocks and their subsequent conversions to fuels. The biofuels contain various amounts of oxygen, and this has a significant influence on exhaust emission. This oxygen content has been considered in order to investigate its effect on diesel engine exhaust emissions. The experiments have been conducted with a heavy duty diesel engine and various oxygenated fuels. It is found that the amount of oxygen in the fuel has a high level of influence on its exhaust emissions, and this provides agreement with diesel emissions results such as PN reduction. By increasing the amount of oxygen in the blend (by adding more biofuel), the particulate number (PN) is reduced and NOx increases gradually. However, the variation of PN and NOx are not similar for waste cooking biodiesel (WCBD) and butanol blend, even though their oxygen content are the same in the blends. This is due to the source of the biofuel and their internal chemistry.

Levels and predictors of exercise referral scheme uptake and adherence: A systematic review

Background The effectiveness of exercise referral schemes (ERS) is influenced by uptake and adherence to the scheme. The identification of factors influencing low uptake and adherence could lead to the refinement of schemes to optimise investment. Objectives To quantify the levels of ERS uptake and adherence and to identify factors predictive of uptake and adherence. Methods A systematic review and meta-analysis was undertaken. MEDLINE, EMBASE, PsycINFO, Cochrane Library, ISI WOS, SPORTDiscus and ongoing trial registries were searched (to October 2009) and included study references were checked. Included studies were required to report at least one of the following: (1) a numerical measure of ERS uptake or adherence and (2) an estimate of the statistical association between participant demographic or psychosocial factors (eg, level of motivation, self-efficacy) or programme factors and uptake or adherence to ERS. Results Twenty studies met the inclusion criteria, six randomised controlled trials (RCTs) and 14 observational studies. The pooled level of uptake in ERS was 66% (95% CI 57% to 75%) across the observational studies and 81% (95% CI 68% to 94%) across the RCTs. The pooled level of ERS adherence was 49% (95% CI 40% to 59%) across the observational studies and 43% (95% CI 32% to 54%) across the RCTs. Few studies considered anything other than gender and age. Women were more likely to begin an ERS but were less likely to adhere to it than men. Older people were more likely to begin and adhere to an ERS. Limitations Substantial heterogeneity was evident across the ERS studies. Without standardised definitions, the heterogeneity may have been reflective of differences in methods of defining uptake and adherence across studies. Conclusions To enhance our understanding of the variation in uptake and adherence across ERS and how these variations might affect physical activity outcomes, future trials need to use quantitative and qualitative methods.

Information flow, trading activity and commodity futures volatility

Based on unique news data relating to gold and crude oil, we investigate how news volume and sentiment, shocks in trading activity, market depth and trader positions unrelated to information flow covary with realized volatility. Positive shocks to the rate of news arrival, and negative shocks to news sentiment exhibit the largest effects. After controlling for the level of news flow and cross-correlations, net trader positions play only a minor role. These findings are at odds with those of [Wang (2002a). The Journal of Futures Markets, 22, 427–450; Wang (2002b). The Financial Review, 37, 295–316], but are consistent with the previous literature which doesn't find a strong link between volatility and trader positions.

Embodied energy of service trading in Hong Kong

Purpose Energy is a resource of strategic importance for high density cities. International trade reshapes the urban economy and industrial structure of a city, which will indirectly affect energy use. As an international trade hub, Hong Kong relies on the import and export of services. Energy performance in the international trading of these services needs to be properly understood and assessed for Hong Kong’s urban renewal efforts. Design/methodology/approach This study evaluates Hong Kong’s embodied energy in service trades based on an input-output analysis. The three criteria used for assessment include trading areas, industry sector, and trade balance. Findings Analyzed by region, results show that Mainland China and the USA are the two largest sources of embodied energy in imports of services, while Mainland China and Japan are the two largest destinations of exports. In terms of net embodied energy transfer, Hong Kong mainly receives net energy import from Mainland China and the USA and supplies net energy export to Japan, the UK and Taiwan. Among industry sectors, Manufacturing services, Transport and Travel contribute most significantly to the embodied energy in Hong Kong’s imported services, while Transport and Travel contribute most to the energy embodied in exported services. Originality/value This study identifies the characteristics of energy consumption of service trading and establishes a feasible approach to analyze energy performance of service trade in energy-deficient Hong Kong for the first time. It provides necessary understanding and foundation for developing energy strategies in a service-based, high density urban economy.

Establishing turf grass increases soil greenhouse gas emissions in peri-urban environments

Urbanization is becoming increasingly important in terms of climate change and ecosystem functionality worldwide. We are only beginning to understand how the processes of urbanization influence ecosystem dynamics and how peri-urban environments contribute to climate change. Brisbane in South East Queensland (SEQ) currently has the most extensive urban sprawl of all Australian cities. This leads to substantial land use changes in urban and peri-urban environments and the subsequent gaseous emissions from soils are to date neglected for IPCC climate change estimations. This research examines how land use change effects methane (CH4) and nitrous oxide (N2O) fluxes from peri-urban soils and consequently influences the Global Warming Potential (GWP) of rural ecosystems in agricultural use undergoing urbanization. Therefore, manual and fully automated static chamber measurements determined soil gas fluxes over a full year and an intensive sampling campaign of 80 days after land use change. Turf grass, as the major peri-urban land cover, increased the GWP by 415 kg CO2-e ha 1 over the first 80 days after conversion from a well-established pasture. This results principally from increased daily average N2O emissions of 0.5 g N2O ha-1 d-1 from the pasture to 18.3 g N2O ha-1 d-1 from the turf grass due to fertilizer application during conversion. Compared to the native dry sclerophyll eucalypt forest, turf grass establishment increases the GWP by another 30 kg CO2-e ha 1. The results presented in this study clearly indicate the substantial impact of urbanization on soil-atmosphere gas exchange in form of non-CO2 greenhouse gas emissions particularly after turf grass establishment.

Carbon dioxide emissions in the short run: The rate and sources of economic growth matter

This paper investigates the short-run effects of economic growth on carbon dioxide emissions from the combustion of fossil fuels and the manufacture of cement for 189 countries over the period 1961-2010. Contrary to what has previously been reported, we conclude that there is no strong evidence that the emissions-income elasticity is larger during individual years of economic expansion as compared to recession. Significant evidence of asymmetry emerges when effects over longer periods are considered. We find that economic growth tends to increase emissions not only in the same year, but also in subsequent years. Delayed effects - especially noticeable in the road transport sector - mean that emissions tend to grow more quickly after booms and more slowly after recessions. Emissions are more sensitive to fluctuations in industrial value added than agricultural value added, with services being an intermediate case. On the expenditure side, growth in consumption and growth in investment have similar implications for national emissions. External shocks have a relatively large emissions impact, and the short-run emissions-income elasticity does not appear to decline as incomes increase. Economic growth and emissions have been more tightly linked in fossil-fuel rich countries.

Decomposition of energy-related CO2 emissions in Australia: Challenges and policy implications

Changes in energy-related CO2 emissions aggregate intensity, total CO2 emissions and per-capita CO2 emissions in Australia are decomposed by using a Logarithmic Mean Divisia Index (LMDI) method for the period 1978-2010. Results indicate improvements in energy efficiency played a dominant role in the measured 17% reduction in CO2 emissions aggregate intensity in Australia over the period. Structural changes in the economy, such as changes in the relative importance of the services sector vis-à-vis manufacturing, have also played a major role in achieving this outcome. Results also suggest that, without these mitigating factors, income per capita and population effects could well have produced an increase in total emissions of more than 50% higher than actually occurred over the period. Perhaps most starkly, the results indicate that, without these mitigating factors, the growth in CO2 emissions per capita could have been over 150% higher than actually observed. Notwithstanding this, the study suggests that, for Australia to meet its Copenhagen commitment, the relative average per annum effectiveness of these mitigating factors during 2010-2020 probably needs to be almost three times what it was in the 2005-2010 period-a very daunting challenge indeed for Australia's policymakers.

Changes in CO2 emissions over business cycle recessions and expansions in the United States: A decomposition analysis

This paper examines the asymmetry of changes in CO2 emissions over business cycle recessions and expansions using yearly data from 1949 and monthly data from 1973 for the United States (US). In addition, decomposition analysis is applied to investigate the relative roles of various proximate contributing factors to observed changes in total and per capita CO2 emissions and emissions intensity, over business cycle phases. The results suggest, inter alia, that aggregate emissions and emissions intensity reduce much faster in contractions than they increase in expansions. In addition, unlike the three previous expansions, in the most recent post-GFC US expansion, emissions per capita have continued to decline, and at a rate very similar to the rate of reduction in preceding contractions. This suggests the real possibility that the most recent contraction may have had an ongoing impact on the path of per capita emissions well beyond the immediate impact experienced during the contraction itself.

Co2 emissions and income trajectory in Australia: The role of technological change

This study investigates the relationship between per capita carbon dioxide (CO2) emissions and per capita GDP in Australia, while controlling for technological state as measured by multifactor productivity and export of black coal. Although technological progress seems to play a critical role in achieving long term goals of CO2 reduction and economic growth, empirical studies have often considered time trend to proxy technological change. However, as discoveries and diffusion of new technologies may not progress smoothly with time, the assumption of a deterministic technological progress may be incorrect in the long run. The use of multifactor productivity as a measure of technological state, therefore, overcomes the limitations and provides practical policy directions. This study uses recently developed bound-testing approach, which is complemented by Johansen- Juselius maximum likelihood approach and a reasonably large sample size to investigate the cointegration relationship. Both of the techniques suggest that cointegration relationship exists among the variables. The long-run and short-run coefficients of CO2 emissions function is estimated using ARDL approach. The empirical findings in the study show evidence of the existence of Environmental Kuznets Curve type relationship for per capita CO2 emissions in the Australian context. The technology as measured by the multifactor productivity, however, is not found as an influencing variable in emissionsincome trajectory.

Energy-output linkages in Australia: Implications for emissions reduction policies

The study investigates the long-run and dynamic relationships between energy consumption and output in Australia using a multivariate cointegration and causality framework. Using both Engle-Granger and Johansen cointegration approaches, the study finds that energy consumption and real Gross Domestic Product are cointegrated. The Granger causality tests suggest bidirectional Granger causality between energy consumption and real GDP, and Granger endogeineity in the system. Since the energy sector largely contributes to carbon emissions in Australia, we suggest that direct measures to reduce carbon by putting constraints on the energy consumption would pose significant economic costs for the Australian economy.

Greenwashing the Trans-Pacific Partnership: Fossil fuels, the environment, and climate change

There has been much controversy over the Trans-Pacific Partnership (TPP) – a plurilateral trade agreement involving a dozen nations from throughout the Pacific Rim – and its impact upon the environment, biodiversity, and climate change. The secretive treaty negotiations involve Australia and New Zealand; countries from South East Asia such as Brunei Darussalam, Malaysia, Singapore, Vietnam, and Japan; the South American nations of Peru and Chile; and the members of the 1994 North American Free Trade Agreement (NAFTA), Canada, Mexico and the United States. There was an agreement reached between the parties in October 2015. The participants asserted: ‘We expect this historic agreement to promote economic growth, support higher-paying jobs; enhance innovation, productivity and competitiveness; raise living standards; reduce poverty in our countries; and to promote transparency, good governance, and strong labor and environmental protections.’ The final texts of the agreement were published in November 2015. There has been discussion as to whether other countries – such as Indonesia, the Philippines, and South Korea – will join the deal. There has been much debate about the impact of this proposed treaty upon intellectual property, the environment, biodiversity and climate change. There have been similar concerns about the Trans-Atlantic Trade and Investment Partnership (TTIP) – a proposed trade agreement between the United States and the European Union. In 2011, the United States Trade Representative developed a Green Paper on trade, conservation, and the environment in the context of the TPP. In its rhetoric, the United States Trade Representative has maintained that it has been pushing for strong, enforceable environmental standards in the TPP. In a key statement in 2014, the United States Trade Representative Mike Froman insisted: ‘The United States’ position on the environment in the Trans-Pacific Partnership negotiations is this: environmental stewardship is a core American value, and we will insist on a robust, fully enforceable environment chapter in the TPP or we will not come to agreement.’ The United States Trade Representative maintained: ‘Our proposals in the TPP are centered around the enforcement of environmental laws, including those implementing multilateral environmental agreements (MEAs) in TPP partner countries, and also around trailblazing, first-ever conservation proposals that will raise standards across the region’. Moreover, the United States Trade Representative asserted: ‘Furthermore, our proposals would enhance international cooperation and create new opportunities for public participation in environmental governance and enforcement.’ The United States Trade Representative has provided this public outline of the Environment Chapter of the TPP: A meaningful outcome on environment will ensure that the agreement appropriately addresses important trade and environment challenges and enhances the mutual supportiveness of trade and environment. The Trans-Pacific Partnership countries share the view that the environment text should include effective provisions on trade-related issues that would help to reinforce environmental protection and are discussing an effective institutional arrangement to oversee implementation and a specific cooperation framework for addressing capacity building needs. They also are discussing proposals on new issues, such as marine fisheries and other conservation issues, biodiversity, invasive alien species, climate change, and environmental goods and services. Mark Linscott, an assistant Trade Representative testified: ‘An environment chapter in the TPP should strengthen country commitments to enforce their environmental laws and regulations, including in areas related to ocean and fisheries governance, through the effective enforcement obligation subject to dispute settlement.’ Inside US Trade has commented: ‘While not initially expected to be among the most difficult areas, the environment chapter has emerged as a formidable challenge, partly due to disagreement over the United States proposal to make environmental obligations binding under the TPP dispute settlement mechanism’. Joshua Meltzer from the Brookings Institute contended that the trade agreement could be a boon for the protection of the environment in the Pacific Rim: Whether it is depleting fisheries, declining biodiversity or reduced space in the atmosphere for Greenhouse Gas emissions, the underlying issue is resource scarcity. And in a world where an additional 3 billion people are expected to enter the middle class over the next 15 years, countries need to find new and creative ways to cooperate in order to satisfy the legitimate needs of their population for growth and opportunity while using resources in a manner that is sustainable for current and future generations. The TPP parties already represent a diverse range of developed and developing countries. Should the TPP become a free trade agreement of the Asia-Pacific region, it will include the main developed and developing countries and will be a strong basis for building a global consensus on these trade and environmental issues. The TPP has been promoted by its proponents as a boon to the environment. The United States Trade Representative has maintained that the TPP will protect the environment: ‘The United States’ position on the environment in the TPP negotiations is this: environmental stewardship is a core American value, and we will insist on a robust, fully enforceable environment chapter in the TPP or we will not come to agreement.’ The United States Trade Representative discussed ‘Trade for a Greener World’ on World Environment Day. Andrew Robb, at the time the Australian Trade and Investment Minister, vowed that the TPP will contain safeguards for the protection of the environment. In November 2015, after the release of the TPP text, Rohan Patel, the Special Assistant to the President and Deputy Director of Intergovernmental Affairs, sought to defend the environmental credentials of the TPP. He contended that the deal had been supported by the Nature Conservancy, the International Fund for Animal Welfare, the Joint Ocean Commission Initiative, the World Wildlife Fund, and World Animal Protection. The United States Congress, though, has been conflicted by the United States Trade Representative’s arguments about the TPP and the environment. In 2012, members of the United States Congress - including Senator Ron Wyden (D-OR), Olympia Snowe (R-ME), and John Kerry (D-MA) – wrote a letter, arguing that the trade agreement needs to provide strong protection for the environment: ‘We believe that a '21st century agreement' must have an environment chapter that guarantees ongoing sustainable trade and creates jobs, and this is what American businesses and consumers want and expect also.’ The group stressed that ‘A binding and enforceable TPP environment chapter that stands up for American interests is critical to our support of the TPP’. The Congressional leaders maintained: ‘We believe the 2007 bipartisan congressional consensus on environmental provisions included in recent trade agreements should serve as the framework for the environment chapter of the TPP.’ In 2013, senior members of the Democratic leadership expressed their opposition to granting President Barack Obama a fast-track authority in respect of the TPP House of Representatives Minority Leader Nancy Pelosi said: ‘No on fast-track – Camp-Baucus – out of the question.’ Senator Majority leader Harry Reid commented: ‘I’m against Fast-Track: Everyone would be well-advised to push this right now.’ Senator Elizabeth Warren has been particularly critical of the process and the substance of the negotiations in the TPP: From what I hear, Wall Street, pharmaceuticals, telecom, big polluters and outsourcers are all salivating at the chance to rig the deal in the upcoming trade talks. So the question is, Why are the trade talks secret? You’ll love this answer. Boy, the things you learn on Capitol Hill. I actually have had supporters of the deal say to me ‘They have to be secret, because if the American people knew what was actually in them, they would be opposed. Think about that. Real people, people whose jobs are at stake, small-business owners who don’t want to compete with overseas companies that dump their waste in rivers and hire workers for a dollar a day—those people, people without an army of lobbyists—they would be opposed. I believe if people across this country would be opposed to a particular trade agreement, then maybe that trade agreement should not happen. The Finance Committee in the United States Congress deliberated over the Trans-Pacific Partnership negotiations in 2014. The new chair Ron Wyden has argued that there needs to be greater transparency in trade. Nonetheless, he has mooted the possibility of a ‘smart-track’ to reconcile the competing demands of the Obama Administration, and United States Congress. Wyden insisted: ‘The new breed of trade challenges spawned over the last generation must be addressed in imaginative new policies and locked into enforceable, ambitious, job-generating trade agreements.’ He emphasized that such agreements ‘must reflect the need for a free and open Internet, strong labor rights and environmental protections.’ Elder Democrat Sander Levin warned that the TPP failed to provide proper protection for the environment: The TPP parties are considering a different structure to protect the environment than the one adopted in the May 10 Agreement, which directly incorporated seven multilateral environmental agreements into the text of past trade agreements. While the form is less important than the substance, the TPP must provide an overall level of environmental protection that upholds and builds upon the May 10 standard, including fully enforceable obligations. But many of our trading partners are actively seeking to weaken the text to the point of falling short of that standard, including on key issues like conservation. Nonetheless, 2015, President Barack Obama was able to secure the overall support of the United States Congress for his ‘fast-track’ authority. This was made possible by the Republicans and dissident Democrats. Notably, Oregon Senator Ron Wyden switched sides, and was transformed from a critic of the TPP to an apologist for the TPP. For their part, green political parties and civil society organisations have been concerned about the secretive nature of the negotiations; and the substantive implications of the treaty for the environment. Environmental groups and climate advocates have been sceptical of the environmental claims made by the White House for the TPP. The Green Party of Aotearoa New Zealand, the Australian Greens and the Green Party of Canada have released a joint declaration on the TPP observing: ‘More than just another trade agreement, the TPP provisions could hinder access to safe, affordable medicines, weaken local content rules for media, stifle high-tech innovation, and even restrict the ability of future governments to legislate for the good of public health and the environment’. In the United States, civil society groups such as the Sierra Club, Public Citizen, WWF, the Friends of the Earth, the Rainforest Action Network and 350.org have raised concerns about the TPP and the environment. Allison Chin, President of the Sierra Club, complained about the lack of transparency, due process, and public participation in the TPP talks: ‘This is a stealth affront to the principles of our democracy.’ Maude Barlow’s The Council of Canadians has also been concerned about the TPP and environmental justice. New Zealand Sustainability Council executive director Simon Terry said the agreement showed ‘minimal real gains for nature’. A number of organisations have joined a grand coalition of civil society organisations, which are opposed to the grant of a fast-track. On the 15th January 2013, WikiLeaks released the draft Environment Chapter of the TPP - along with a report by the Chairs of the Environmental Working Group. Julian Assange, WikiLeaks' publisher, stated: ‘Today's WikiLeaks release shows that the public sweetener in the TPP is just media sugar water.’ He observed: ‘The fabled TPP environmental chapter turns out to be a toothless public relations exercise with no enforcement mechanism.’ This article provides a critical examination of the draft Environment Chapter of the TPP. The overall argument of the article is that the Environment Chapter of the TPP is an exercise in greenwashing – it is a public relations exercise by the United States Trade Representative, rather than a substantive regime for the protection of the environment in the Pacific Rim. Greenwashing has long been a problem in commerce, in which companies making misleading and deceptive claims about the environment. In his 2012 book, Greenwash: Big Brands and Carbon Scams, Guy Pearse considers the rise of green marketing and greenwashing. Government greenwashing is also a significant issue. In his book Storms of My Grandchildren, the climate scientist James Hansen raises his concerns about government greenwashing. Such a problem is apparent with the TPP – in which there was a gap between the assertions of the United States Government, and the reality of the agreement. This article contends that the TPP fails to meet the expectations created by President Barack Obama, the White House, and the United States Trade Representative about the environmental value of the agreement. First, this piece considers the relationship of the TPP to multilateral environmental treaties. Second, it explores whether the provisions in respect of the environment are enforceable. Third, this article examines the treatment of trade and biodiversity in the TPP. Fourth, this study considers the question of marine capture fisheries. Fifth, there is an evaluation of the cursory text in the TPP on conservation. Sixth, the article considers trade in environmental services under the TPP. Seventh, this article highlights the tensions between the TPP and substantive international climate action. It is submitted that the TPP undermines effective and meaningful government action and regulation in respect of climate change. The conclusion also highlights that a number of other chapters of the TPP will impact upon the protection of the environment – including the Investment Chapter, the Intellectual Property Chapter, the Technical Barriers to Trade Chapter, and the text on public procurement.

Denitrification losses from an intensively managed sub-tropical pasture: Impact of soil moisture on the partitioning of N2 and N2O emissions

Intensively managed pastures in subtropical Australia under dairy production are nitrogen (N) loaded agro-ecosystems, with an increased pool of N available for denitrification. The magnitude of denitrification losses and N2:N2O partitioning in these agro-ecosystems is largely unknown, representing a major uncertainty when estimating total N loss and replacement. This study investigated the influence of different soil moisture contents on N2 and N2O emissions from a subtropical dairy pasture in Queensland, Australia. Intact soil cores were incubated over 15 days at 80% and 100% water-filled pore space (WFPS), after the application of 15N labelled nitrate, equivalent to 50 kg N ha−1. This setup enabled the direct quantification of N2 and N2O emissions following fertilisation using the 15N gas flux method. The main product of denitrification in both treatments was N2. N2 emissions exceeded N2O emissions by a factor of 8 ± 1 at 80% WFPS and a factor of 17 ± 2 at 100% WFPS. The total amount of N-N2 lost over the incubation period was 21.27 kg ± 2.10 N2-N ha−1 at 80% WFPS and 25.26 kg ± 2.79 kg ha−1 at 100% WFPS respectively. N2 emissions remained high at 100% WFPS, while related N2O emissions decreased. At 80% WFPS, N2 emissions increased constantly over time while N2O fluxes declined. Consequently, N2/(N2 + N2O) product ratios increased over the incubation period in both treatments. N2/(N2 + N2O) product ratios responded significantly to soil moisture, confirming WFPS as a key driver of denitrification. The substantial amount of fertiliser lost as N2 reveals the agronomic significance of denitrification as a major pathway of N loss for sub-tropical pastures at high WFPS and may explain the low fertiliser N use efficiency observed for these agro-ecosystems.

Legumes or nitrification inhibitors to reduce {N2O} emissions from subtropical cereal cropping systems in Oxisols?

The DAYCENT biogeochemical model was used to investigate how the use of fertilizers coated with nitrification inhibitors and the introduction of legumes in the crop rotation can affect subtropical cereal production and {N2O} emissions. The model was validated using comprehensive multi-seasonal, high-frequency dataset from two field investigations conducted on an Oxisol, which is the most common soil type in subtropical regions. Different N fertilizer rates were tested for each N management strategy and simulated under varying weather conditions. DAYCENT was able to reliably predict soil N dynamics, seasonal {N2O} emissions and crop production, although some discrepancies were observed in the treatments with low or no added N inputs and in the simulation of daily {N2O} fluxes. Simulations highlighted that the high clay content and the relatively low C levels of the Oxisol analyzed in this study limit the chances for significant amounts of N to be lost via deep leaching or denitrification. The application of urea coated with a nitrification inhibitor was the most effective strategy to minimize {N2O} emissions. This strategy however did not increase yields since the nitrification inhibitor did not substantially decrease overall N losses compared to conventional urea. Simulations indicated that replacing part of crop N requirements with N mineralized by legume residues is the most effective strategy to reduce {N2O} emissions and support cereal productivity. The results of this study show that legumes have significant potential to enhance the sustainable and profitable intensification of subtropical cereal cropping systems in Oxisols.

Non-linear response of soil N2O emissions to nitrogen fertiliser in a cotton-fallow rotation in sub-tropical Australia

Nitrogen fertiliser is a major source of atmospheric N2O and over recent years there is growing evidence for a non-linear, exponential relationship between N fertiliser application rate and N2O emissions. However, there is still high uncertainty around the relationship of N fertiliser rate and N2O emissions for many cropping systems. We conducted year-round measurements of N2O emission and lint yield in four N rate treatments (0, 90, 180 and 270 kg N ha-1) in a cotton-fallow rotation on a black vertosol in Australia. We observed a nonlinear exponential response of N2O emissions to increasing N fertiliser rates with cumulative annual N2O emissions of 0.55 kg N ha-1, 0.67kg N ha-1, 1.07 kg N ha-1 and 1.89 kg N ha-1 for the four respective N fertiliser rates while no N response to yield occurred above 180N. The N fertiliser induced annual N2O EF factors increased from 0.13% to 0.29% and 0.50% for the 90N, 180N and 270N treatments respectively, significantly lower than the IPCC Tier 1 default value (1.0 %). This non-linear response suggests that an exponential N2O emissions model may be more appropriate for use in estimating emission of N2O from soils cultivated to cotton in Australia. It also demonstrates that improved agricultural N management practices can be adopted in cotton to substantially reduce N2O emissions without affecting yield potential.