Effect of soil texture and wheat plants on N₂O fluxes: a lysimeter study

Agricultural soils are a major source of nitrous oxide (N2O) emissions and an understanding of factors regulating such emissions across contrasting soil types is critical for improved estimation through modelling and mitigation of N2O. In this study we investigated the role of soil texture and its interaction with plants in regulating the N2O fluxes in agricultural systems. A measurement system that combined weighing lysimeters with automated chambers was used to directly compare continuously measured surface N2O fluxes, leaching losses of water and nitrogen and evapotranspiration in three contrasting soils types of the Riverine Plain, NSW, Australia. The soils comprised a deep sand, a loam and a clay loam with and without the presence of wheat plants. All soils were under the same fertilizer management and irrigation was applied according to plant water requirements. In fallow soils, texture significantly affected N2O emissions in the order clay loam > loam > sand. However, when planted, the difference in N2O emissions among the three soils types became less pronounced. Nitrous oxide emissions were 6.2 and 2.4 times higher from fallow clay loam and loam cores, respectively, compared with cores planted with wheat. This is considered to be due to plant uptake of water and nitrogen which resulted in reduced amounts of soil water and available nitrogen, and therefore less favourable soil conditions for denitrification. The effect of plants on N2O emissions was not apparent in the coarse textured sandy soil probably because of aerobic soil conditions, likely caused by low water holding capacity and rapid drainage irrespective of plant presence resulting in reduced denitrification activity. More than 90% of N2O emissions were derived from denitrification in the fine-textured clay loam-determined for a two week period using K15NO3 fertilizer. The proportion of N2O that was not derived from K15NO3 was higher in the coarse-textured sand and loam, which may have been derived from soil N through nitrification or denitrification of mineralized N. Water filled pore space was a poorer predictor of N2O emissions compared with volumetric water content because of variable bulk density among soil types. The data may better inform the calibration of greenhouse gas prediction models as soil texture is one of the primary factors that explain spatial variation in N2O emissions by regulating soil oxygen. Defining the significance of N2O emissions between planted and fallow soils may enable improved yield scaled N2O emission assessment, water and nitrogen scheduling in the pre-watering phase during early crop establishment and within rotations of irrigated arable cropping systems.

Modelling greenhouse gas emissions for Australian residential building construction

International pressure to reduce greenhouse gas emissions has forced many countries to look beyond 'demand side' measures. Several industry sectors are examining indirect requirements for energy and other resources that involve significant greenhouse gas emissions. The operation of buildings is responsible for approximately one quarter of greenhouse gas emissions in Australia. Moreover, he construction process consumes vast quantities of raw materials and complex goods and services each year. Each of the processes required for the provision of these products requires energy, and most of this is fossil fuel based. A national model of greenhouse gas emissions is required for residential building construction, to indicate where emissions reduction strategies should focus. A disaggregated input-output model is developed for the Australian residential building construction sector, and recommendations are made about how this model can be used in the development of policies of emissions mitigation for both the sector and individual residential buildings.

Building materials selection: greenhouse strategies for built facilities

This paper aims to consider the embodied energy of building materials in the context of greenhouse gas emission mitigation strategies. Previous practice and research are highlighted where they have the potential to influence design decisions. Latest embodied energy figures are indicated, and the implications of applying these figures to whole buildings are discussed. Several practical examples are given to aid building designers in the selection of building materials for reduced overall life cycle greenhouse gas emissions.

Comparative greenhouse emissions anayalsis of domestic solar hot water systems

It is commonly assumed that solar hot water systems save energy and reduce greenhouse emissions relative to conventional fossil fuel-powered systems. Very rarely has the life-cycle greenhouse emissions (including the embodied greenhouse emissions of manufacture) of solar hot water systems been analysed. The extent to which solar hot water systems can reduce emissions compared with conventional systems can be shown through a comparative life-cycle greenhouse emissions analysis. This method determined the time it takes for these net greenhouse emissions savings to occur, or the 'emissions payback period'. This paper presents the results of a life-cycle greenhouse emissions analysis of solar hot water systems in comparison with conventional hot water systems for a southern (Melbourne) and a northern (Brisbane) Australian city.

Does firefighting foam affect the growth of some Australian native plants?

Firefighting foams (Class A foams) are an effective and widespread firefighting tool, and are frequently used in environmentally sensitive areas. They are known to be ecologically damaging in aquatic environments; however, their impacts at the plant species or ecosystem level are relatively unknown. Reports of shoot damage to plants, suppressed flowering and changes in plant community composition suggest that the environmental damage caused by their use may be unacceptable. Applications of four levels of foam to seedlings of seven Australian plant species, from five representative and widespread families, showed no detectable impacts on a range of vegetative growth characteristics. The results are encouraging for continued use of firefighting foam in sensitive natural habitats.

The influence of housing size, style and location on energy and greenhouse gas emissions

Concern about the growth of greenhouse gas emissions in Victoria has prompted the introduction of legislation to improve the thermal performance of the residential building envelope. Unfortunately, the size of the house is not considered in the rating tool that underpins the legislation. The energy embodied in the constructional materials is also not considered although it too is directly related to the size of the house. Another intrinsic factor relating residential housing energy and greenhouse gas emissions is the location of the residence and the travel preferences of the homeowner. The relationship between the operational, embodied and travel energy associated with a typical residential scenario in Melbourne over the last 50 years is examined in this paper. The analysis found that by the year 2000, the energy associated with work-related travel (44%) now exceeds the operational energy (37%). In terms of greenhouse gas emissions, the contribution from travel energy is almost double that from operational energy (28%).

An evaluation of personal greenhouse gas calculators

Personal greenhouse gas calculators (PGGC) are important tools to raise awareness of the impact of personal behaviour on carbon dioxide emissions. Per capita, Australians are the highest emitters of greenhouse gases in the world and the task for them to reduce emissions to sustainable levels will be particularly challenging. This paper reviews six PGGC promoted in Australia and evaluates them for their consistency. The emissions for an individual currently practicing a modest green lifestyle are calculated and compared. Emission calculations were found to differ by an order of magnitude in some cases. It was also found that users of PGGC are not adequately informed about the limitations of the calculators. The adoption of modest and radical green lifestyles reduced greenhouse gas emissions to 83% and 53% of the average Australian, indicating that behavioural changes by consumers alone will be insufficient to reduce emissions to sustainable levels.

Estimating the increasing cost of commercial buildings in Australia due to greenhouse emissions trading

The ratification of the Kyoto Protocol by most industrial nations will result in an international greenhouse emissions trading market by or before 2008. Calculating the quantity of embodied energy in commercial buildings has therefore taken on added significance because it is in the creation of energy that most greenhouse gas that causes global warming is released. For energy efficient commercial buildings in Australia, the embodied energy can typically represent between 10 and 20 years of operational energy. When greenhouse emissions trading is introduced in Australia the cost of energy will rise significantly, particularly electricity which relies primarily on burning fossil fuels for generation. This will affect not only the operating energy costs of buildings (light, power & heating/cooling) but also the cost of building materials and construction. Early estimates of the potential cost of future greenhouse emission permits in Australia vary between $IO/tonne to $180Itonne. This cost would be imposed primarily on the producers of energy and passed on by them to consumers via higher energy costs. For a typical commercial building this could lead to an increase in the total procurement cost of buildings of up to 20% due to the energy embodied during the construction or refurbishment of the building. To assist in evaluating these potential cost increases McKean & Park, Sinclair Knight Merz and Deakin University have developed a web-based Carbon Cost Calculator for commercial buildings.