Jim Rasmussen

Elucidating the Key Member of a Linuron-Mineralizing Bacterial Community by PCR and Reverse Transcription-PCR Denaturing Gradient Gel Electrophoresis 16S rRNA Gene Fingerprinting and Cultivation

ABSTRACT A bacterial community from Danish agricultural soil was enriched with linuron [N-(3,4-dichlorophenyl)-N′-methoxy-N′-methylurea] as the sole carbon and nitrogen source. The community mineralized [ring-U-14C]linuron completely to 14CO2 and 14C-biomass. Denaturing gradient gel electrophoresis analysis and cultivation revealed that a Variovorax sp. was responsible for the mineralization activity.

Forbs enhance productivity of unfertilised grass-clover leys and support low-carbon bioenergy

Intensively managed grasslands are dominated by highly productive grass-clover mixtures. Increasing crop diversity by inclusion of competitive forbs may enhance biomass production and sustainable biofuel production. Here we examined if one or all of three forbs (chicory, Cichorium intybus L.; caraway, Carum carvi L.; plantain, Plantago lanceolata L.) included in ryegrass-red clover mixtures enhanced above- and below-ground productivity, and assessed their biofuel potentials, based on a three-year experiment with and without fertilisation as cattle slurry. We determined herbage yield, standing root biomass, and estimated methane energy output and greenhouse gas (GHG) emissions per energy unit using life cycle assessment. Results showed that plantain-containing grass-clover mixtures significantly increased herbage yield, while chicory- or caraway-containing mixtures maintained similar yields to the grass-clover mixture. Standing root biomass of the grass-clover mixture was enhanced by inclusion of caraway and plantain, with that of plantain further enhanced by fertilisation. The highest methane energy output was achieved in plantain-containing grass-clover mixtures. All unfertilised mixtures achieved the 60% reduction in GHG emissions compared to fossil fuel, whereas all fertilised mixtures did not meet the 60% reduction target. These findings suggest that including competitive forbs such as plantain in grass-clover mixtures enhances productivity, supporting low-carbon footprint bioenergy production.

Thin-layer chromatographic methods for the analysis of eighteen different 14 C-labeled pesticides

In recent decades xenobiotics introduced into the environment have been of major interest to the public. One of the largest groups of xenobiotic compounds is the pesticides, which are widely used for pest and disease management in agriculture, households, and public health. Studies of the fate of pesticides in the environment have mainly focused on the parent compounds, but the discovery of degradation products [1, 2] in ground water has raised growing concern about the role of metabolites which may be as harmful as the parent compounds, or even more so [3, 4].

Effect of plant species and temperature on amino acid release from plant material

Agricultural crop production is largely dependent on inputs of mineral fertilizers. Mineral fertilizer prices are expected to rise as the competition for fossil energy increases. In order to increase the sustainability of crop production, alternatives to commercial mineral fertilizers are needed. Organic residues and fresh biomass are potentially important sources of nitrogen (N) in crop production. A study was conducted to investigate the impact of temperature on the release rate and profile of amino acids from soybean seeds (Glycine max L.) and fresh young shoots of chicory (Cichorium intybus), alfalfa (Medicago sativa) and red clover (Trifolium pratense) under anaerobic conditions. Plant material was incubated in water at either 15 °C or 35 °C, and the temporal release of total N, inorganic N, organic N and amino acids was measured during the 240 h incubation period. Amino acids and other organic N sources constituted significant proportions (20–84%) of the soluble N that was released. The contribution of organic N compounds to total N released decreased when the incubation temperature was raised from 15 °C to 35 °C, whereas the increase in temperature resulted in a higher total N release for only alfalfa and soybean. Amino acid profiles differed with plant material, incubation temperature and incubation length, with release patterns that only in a few cases could be described by first-order kinetics. Irrespective of the source, short-term liquid composting solutions will contain a low amino acid:inorganic N ratio with multiple amino acids present, which has to be taken into account when calculating the fertilizer effect. To conclude, this study reports, to our knowledge for the first time, the multiple amino acid release profiles from four different plant materials incubated under anaerobic conditions. The findings demonstrate that amino acids constitute significant proportions of the total N released and that the release patterns only for some amino acids followed first-order kinetics.