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- Schnürer, Johan, 1957-, et al.
(författare)
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Ergosterol Levels and Mould Colony Forming Units in Swedish Grains of Food and Feed Grade
- 1992
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Ingår i: Acta Agriculturae Scandinavica - Section B. - Oslo, Norway : Scandinavian University Press. - 0906-4710 .- 1651-1913. ; 42:4, s. 240-245
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Tidskriftsartikel (refereegranskat)abstract
- Although ergosterol is considered to be a suitable indicator of mould growth in cereal grains, there are few reference values available for Scandinavian conditions. We have determined the ergosterol levels in Swedish grain of different origins: cleaned food-grade wheat from a commercial mill, feed-grade cereals (oats and barley) with different odours and cereals (winter wheat, ''American wheat'', triticale and rye) from various field trials conducted in south-central Sweden in 1990. Specific objectives were to elucidate the relationships between ergosterol levels and numbers of mould colony forming units (CFU) and between ergosterol and grain odour.Ergosterol levels in the food-grade wheat ranged between 2.4 and 2.8 mug/g DW, and between 3.0 and 5.6 mug/g DW in the field trial cereals, while values in most of the feed grain samples ranged from 8-15 mug/g DW The levels agree with other published data for European grains.A positive correlation was found between numbers of colony-forming units and ergosterol concentration. The degree of correlation was higher when numbers of CFU were determined on dichloran-glycerol 18% agar with a low water activity (aw = 0.95) than on malt extract agar (aw = 0.99). There was no agreement between ergosterol levels and grain odour, since even samples described as having a fresh smell had high ergosterol levels. However, the highest level (33 mug/g DW) was found in a sample with a pronounced musty odour, and the lowest (1.1 gg/g DW) in a sample that smelled as if it had been heat damaged.
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| 4. |
- Bahri, Akissa, et al.
(författare)
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Nitrogen source impact on the spatial variability of organic carbon and nitrogen in soil
- 1996
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Ingår i: Soil Science. - : Ovid Technologies (Wolters Kluwer Health). - 0038-075X. ; 161:5, s. 288-297
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Tidskriftsartikel (refereegranskat)abstract
- Sewage sludge amendment of soils leads to an increase in soil fertility, but may induce heterogeneities not initially present in the soil. Spatial variation of soil organic carbon (C) and nitrogen (N) was studied in a heavy clay soil after a sewage sludge application and NPK-treatment (nitrogen, phosphorus, and potassium) using geostatistical approaches. In total, 314 soil samples were taken on two adjacent 40 m × 40 m plots (one sludge-amended and one NPK-treated) at three different scales (scale 40 m: 40 m × 40 m, scale 10 m: 10 m × 10 m, and scale 2.5 m: 2.5 m × 2.5 m). The coefficient of variation almost doubled for both C and N after sludge treatment. Because of this, more samples were needed to estimate mean values for the sludge-amended plot compared with the NPK-treated plot. To estimate the population mean at the 95% confidence level with 10% uncertainty (for all scales and all treatments), 5 to 13 samples were required for C and 4 to 7 for N. The C was spatially more structured compared to N. Semivariances of the sludge-amended plot displayed higher values compared with the NPK-treated plot, except for N at the smallest scale. This was probably due mainly to the sludge characteristics and the application technique of the sewage sludge. Constant semivariance (sill) was reached at ranges up to 15 m for C, but it was often unbounded (>40 m) for N.
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| 6. |
- Berndtsson, Ronny, et al.
(författare)
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Field variability of element concentrations in wheat and soil
- 1995
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Ingår i: Soil Science. - : Ovid Technologies (Wolters Kluwer Health). - 0038-075X. ; 159:5, s. 311-320
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Tidskriftsartikel (refereegranskat)abstract
- Field variability of element concentrations in crops is important to consider for nutrient application as well as for evaluation of environmental hazards. The paper gives an analysis of spatially sampled wheat plant tissue in the field to determine spatial properties of 20 elements for a partly sludge-applied agricultural soil in northern Tunisia. A comparison is made with the spatial variability of geochemical elements in the soil. A geostatistical analysis shows that both soil and plant metal concentrations have a spatial structure with a range of 10 to 30 m for the sampling scale considered. Compared with the soil, element variability in the plant is almost an order of magnitude larger. Consequently, the study indicates that field variability of element concentrations in plants can only partially be explained by the corresponding soil variability.
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| 7. |
- Berndtsson, Ronny, et al.
(författare)
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Soil water and temperature patterns in an arid desert dune sand
- 1996
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Ingår i: Journal of Hydrology. - : Elsevier BV. - 0022-1694. ; 185:1-4, s. 221-240
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Tidskriftsartikel (refereegranskat)abstract
- Under arid natural conditions, soil water content governs and limits the number and size of perennial plant species. Thus, plant-available soil water is the main constraint for sustainable control of desert encroachment. To evaluate possibilities for re-vegetation of bare sand surfaces, soil water and temperature patterns for typical sand dunes in a desert climate were investigated. Bare and vegetated soil transects were selected for observation of soil water content and temperature. The investigated soil transects covered crest-to-crest spacings (about 60 m horizontally and 15 m vertically) in a shifting sand dune area. Observations were made at Shapotou field research station bordering the Tengger Desert in Northwestern China. The paper presents two-dimensional properties of soil water content (0.1-3.0 m depth) and temperature (0-1.0 m depth) before and after rainfall. Rainfall (15-22 mm) affected soil water distribution down to 1.5-2.0 m and temperature distribution down to 1.0 m. Soil water appeared to be transported through the apparently highly pervious and homogeneous sand along the dune slopes. High water contents and, thus, infiltration occurred mainly at the non-sloping parts, i.e. the dune crests and bottoms. Rainfall changed the temperature patterns from a mainly horizontally layered appearance before the rainfall to increasingly vertically shaped patterns.
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| 8. |
- Berndtsson, Ronny, et al.
(författare)
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Soil water, soil chemical and crop variations in a clay soil
- 1996
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Ingår i: Hydrological Sciences Journal. - : Informa UK Limited. - 0262-6667 .- 2150-3435. ; 41:2, s. 171-178
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Tidskriftsartikel (refereegranskat)abstract
- Spatial properties of field soils vary in a complex manner. Especially in arid and semiarid areas, this variability affects plant quality and crop production. An experimental field plot was extensively sampled regarding soil water (378 gravimetrical samples), soil chemical content (314 samples), and crop yield and chemical content (26 samples) at the Cherfech agricultural field research station in Tunisia. Geostatistical analyses were made to gain a better understanding of the in situ variability of soil water, soil chemical and crop properties. Ranges of correlation were found to vary over distances between 5 and over 40 m. Nugget and sill values for semivariograms were almost an order of magnitude larger for crop samples compared to soil samples. The crop yield components appeared to have larger variability as compared to crop chemical components.
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| 10. |
- Krantz-Rülcker, C., et al.
(författare)
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Adsorption of IIB-metals by three common soil fungi-comparison and assessment of importance for metal distribution in natural soil systems
- 1996
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Ingår i: Soil Biology and Biochemistry. - : Elsevier. - 0038-0717 .- 1879-3428. ; 28:7, s. 967-975
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Tidskriftsartikel (refereegranskat)abstract
- Interactions of IIb-elements, Zn, Cd and Hg, with three common soil fungi, Trichoderma harzianum, Penicillium spinulosum and Mortierella isabellina, have been studied. The accumulation of the metals by the fungi was studied as a function of pH at constant ionic strength and at concentration levels of the metals representative of natural systems. Two stages of fungal activity were considered in the experiments. The fungi generally exhibited high affinity for metal ions indicated by distribution coefficients (log K-d, in 1 kg(-1)) of about 3.5 +/- 1, 2.5 +/- 1 and 4 +/- 1 for Zn, Cd and Hg, respectively. The pH-dependence of the accumulation as well as the isotherms at constant pH were similar between the fungi, and the maximum capacities were at least 50 mmoles kg(-1) mycelium (dw). Metal accumulation by starved mycelia was almost independent of pH, while non-starved mycelia in two cases accumulated more metals at low pH. Calculations of the distribution of metals in a model soil system of inorganic and organic constituents as well as fungal biomass indicated that the amounts of metal associated to the fungi are negligible at neutral pH. However, due to the ability of these fungi to accumulate metals independently of pH, the fraction of metals associated to fungal biomass at low pH may be significant, and, in some cases, predominant. This illustrates that the effects of fungi on metal distribution in soil should not be neglected, e.g. during a progressing acidification.
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