Influence of agro-ecosystem modeling approach on the greenhouse gas profiles of wheat-derived biopolymer products.

An approach is presented to include a wider range of factors involved in the nitrogen and carbon cycles in agro-ecosystems than is typical of many Life Cycle Assessments (LCAs) of agriculture-based products. This use results from the process-oriented Denitrification-Decomposition (DNDC, modified version) model. Here we evaluate the effects of using site-specific N(2)O emissions derived from the DNDC model rather than the values derived from the commonly used Intergovernmental Panel on Climate Change (IPCC) Tier 1 empirical model on the results of whole life cycle greenhouse gas (GHG) profiles for wheat-based biopolymer products. Statistical methods were also used to analyze the quality of the DNDC and IPCC outputs and to characterize the uncertainty in the GHG results. The results confirm that the GHG profiles of the wheat-derived biopolymer products are sensitive to how the agricultural system is modeled and uncertainty analyses indicate that DNDC is preferred over the IPCC Tier 1 approach for site-specific LCAs. The former allows inclusion of a wider range of important site-specific agricultural parameters in the LCA, provides for improved quality in the LCA data, and permits better calibration of uncertainty in the LCA inventory.

Effect of arbuscular mycorrhizal fungus (Glomus caledonium) on the accumulation and metabolism of atrazine in maize (Zea mays L.) and atrazine dissipation in soil.

Effects of an arbuscular mycorrhizal (AM) fungus (Glomus caledonium) on accumulation and metabolism of atrazine in maize grown in soil contaminated with different concentrations of atrazine were investigated in a series of pot experiments. Roots of mycorrhizal plants accumulated more atrazine than non-mycorrhizal roots. In contrast, atrazine accumulation in shoot decreased in mycorrhizal compared with non-mycorrhizal plants. No atrazine derivatives were detected in the soil, either with or without mycorrhizal colonization. However, atrazine metabolites, deethylatrazine (DEA) and deisopropylatrazine (DIA), were detected in plant roots and the AM colonization enhanced the metabolism. After plant harvest atrazine concentrations decreased markedly in the soils compared to the initial concentrations. The decreases were the most in rhizosphere soil and then near-rhizosphere soil and the least in bulk soil. Mycorrhizal treatment enhanced atrazine dissipation in the near-rhizosphere and bulk soils irrespective of atrazine application rates.

The impact of tropospheric ozone pollution on trial plot winter wheat yields in Great Britain - an econometric approach.

Numerous experiments have demonstrated reductions in the yields of cereal crops due to tropospheric O(3), with losses of up to 25%. However, the only British econometric study on O(3) impacts on winter wheat yields, found that a 10% increase in AOT40 would decrease yields by only 0.23%. An attempt is made here to reconcile these observations by developing AOT40 maps for Great Britain and matching levels with a large number of standardised trial plot wheat yields from many sites over a 13-year period. Panel estimates (repeated measures on the same plots with time) show a 0.54% decrease in yields and it is hypothesised that plant breeders may have inadvertently selected for O(3) tolerance in wheat. Some support for this is provided by fumigations of cultivars of differing introduction dates. A case is made for the use of econometric as well as experimental studies in prediction of air pollution induced crop loss.

Responses of herbaceous plants to urban air pollution: effects on growth, phenology and leaf surface characteristics.

Vehicle exhaust emissions are a dominant feature of urban environments and are widely believed to have detrimental effects on plants. The effects of diesel exhaust emissions on 12 herbaceous species were studied with respect to growth, flower development, leaf senescence and leaf surface wax characteristics. A diesel generator was used to produce concentrations of nitrogen oxides (NO(x)) representative of urban conditions, in solardome chambers. Annual mean NO(x) concentrations ranged from 77 nl l(-l) to 98 nl l(-1), with NO:NO(2) ratios of 1.4-2.2, providing a good experimental simulation of polluted roadside environments. Pollutant exposure resulted in species-specific changes in growth and phenology, with a consistent trend for accelerated senescence and delayed flowering. Leaf surface characteristics were also affected; contact angle measurements indicated changes in surface wax structure following pollutant exposure. The study demonstrated clearly the potential for realistic levels of vehicle exhaust pollution to have direct adverse effects on urban vegetation.