Infection potential of farm soils as mycorrhizal inocula for Leucaena leucocephala

A greenhouse experiment was conducted to assess the arbuscular mycorrhizal (AM) fungi inoculum potential for Leucaena leucocephala in a range of nutrient-depleted farm soils in western Kenya. Leucaena was grown in 12 uninoculated farm soils with pH 5.0–6.7, with or without rock P and farmyard manure. Root infection, nodulation, and shoot and root weight were determined 25, 46, and 69 days after planting. Spore concentrations in the farm soils at the start of the experiment ranged from 44 to 126 live spores per 100 g dry soil with 6–10 species per soil, principally Scutellospora spp. and Acaulospora spp. Nodulation was absent or poor in all soils, indicating the need for rhizobial inoculation of species belonging to the leucaena crossinoculation group in this agrosystem. Rock-P alone increased final shoot dry weight by a factor of 1.4, manure alone by 1.8, and rock-P plus manure by 1.9, compared with no ameliorant. Root infection with AM fungi was detected in all soils 25 days after planting and increased linearly in the different farm soils to values of 33–65% 69 days after planting. Soil pH and root infection 25 days after planting accounted for much of the variation in final shoot weight among soils with no amelioront (87%). As early root infection increased from 20 to 40% at soil pH 5.0, the predicted final shoot dry weight was doubled, and the response to ameliorants was reduced by two-thirds. The growth responses to increased infection became smaller as pH increased from 5.0 to 6.5.     

Density-dependent habitat selection and the ideal free distribution in marine fish spatial dynamics: considerations and cautions

Current methods and theory used in the study of the spatial dynamics of marine fish are problematic. Positive relationships between population abundance and occupied area are typically interpreted as evidence of density‐dependent habitat selection. However, both abundance and area may co‐vary with an un‐parameterized variable, such as a density‐independent effect. In addition, if density‐dependent habitat selection is present, population growth rates in optimal habitats would be expected to be lower than in marginal habitats. This same pattern can also evolve from a large‐scale, spatially autocorrelated change in a density‐independent factor. The theory underlying density‐dependent habitat selection, the ideal free distribution, can be tautological when no a priori information of how habitat suitability changes with density is known. In this case, an ideal free distribution can be defined for any pattern of habitat‐specific population growth rates. However, these problems are not insurmountable and solutions may be found by considering spatial variation in proxies of fitness and explicitly allowing for the relative importance of habitat selection (density dependent) and environmental (density independent) effects to vary with spatial scale.     

Alkylresorcinols in cereals and cereal products

The alkylresorcinol (AR) content of 8 commonly consumed cereals, 125 Triticum cultivars, milling fractions of wheat and rye, bread, and other cereal products was analyzed. ARs were found in wheat (489-1429 microgram/g), rye (720-761 microgram/g), triticale (439-647 microgram/g), and barley (42-51 microgram/g), but not in rice, oats, maize, sorghum, or millet. One durum wheat variety was found to have an exceptionally low level of ARs (54 microgram/g) compared to other durum wheat varieties (589-751 microgram/g) and Triticumspecies analyzed. The AR content of milling fractions closely followed the ash content and could be used as a marker of the presence of bran in flour. Using hot 1-propanol extraction, all ARs could be extracted from bread, contrary to previous studies which suggested that ARs were destroyed during baking. Cereal products varied greatly in AR content, with those containing wheat bran or whole rye having the highest content.     

Prediction of carbon mineralization rates from different soil physical fractions using diffuse reflectance spectroscopy

Soil carbon (C) mineralization rate is a key indicator of soil functional capacity but it is time consuming to measure using conventional laboratory incubation methods. Recent studies have demonstrated the ability of visible-near infrared spectroscopy (NIRS) for rapid non-destructive determination of soil organic carbon (SOC) and nitrogen (N) concentration. We investigated whether NIRS (350-2500 nm) can predict C mineralization rates in physically fractionated soil aggregates (bulk soil and 6 size fractions, n=108) and free organic matter (2 size fractions, n=27) in aerobically incubated samples from a clayey soil (Ferralsol) and a sandy soil (Arenosol). Incubation reference values were calibrated to first derivative reflectance spectra using partial least-squares regression. Prediction accuracy was assessed by comparing laboratory reference values with NIRS values predicted using full hold-out-one cross-validation. Cross-validated prediction for C respired (500 days) in soil aggregate fractions had an R² of 0.82 while that of C mineralized (300 days) in organic matter fractions was 0.71. Major soil aggregate fractions could be perfectly spectrally discriminated using a 50% random holdout validation sample. NIRS is a promising technique for rapid characterization of potential C mineralization in soils and aggregate fractions. Further work should test the robustness of NIRS prediction of mineralization rates of aggregate fractions across a wide range of soils and spectral mixture models for predicting mass fractions of aggregate size classes.     

Successful treatment of hypereosinophilic syndrome in a dog

An 11-year-old crossbred dog was presented with a history of episodic vomiting, diarrhoea, abdominal discomfort and coughing. These signs had been present for several years. Marked peripheral eosinophilia (10.3 x 10(9)/L) was found. No underlying cause of reactive eosinophilia was apparent. Bone marrow aspiration biopsy showed hyperplasia of the eosinophilic cell line, with some increase in immaturity, although all cells were morphologically normal. There were numerous eosinophils in bronchial wash fluid and eosinophilic infiltrates were evident in biopsies of pancreas, liver, small intestine and colon but not stomach. Hypereosinophilic syndrome was diagnosed. The dog responded well to twice daily treatment with hydroxyurea and prednisolone. Clinical signs are well-controlled 16 months later.     

Implications of soil substrate and land use for properties of fen soils in North-East Germany Part III: Soil quality for grassland use

Abstract

The aim of the study was to analyse aspects of fen soil quality for grassland use with regard to the different topsoil structure and their status of earthification/moorshification (degradation). Fifty fens of different origin, structural status and land use intensity were sampled, analysed and scored by different methods: Visual Soil Assessment, Peerlkamp test and Muencheberg Soil Quality Rating. Suitable soil structure scores were found at different land use intensities with the exception of stock tracks on pastures. These had lower water and air permeability and lower soil strength. Highest visual scores of macrostructure were found where the water table was deeper; while highest overall soil quality scores occurred where the water table was optimum. The accelerated status of moorshification had no effect on the soil quality scores and on the crop yield. At lower levels of soil development (earthification) the crop yield was slightly lower due to higher proportions of inedible plants. It may be concluded that degraded peat soils will have no loss of soil quality and have relatively high soil quality for grassland use if the water table can be managed in a suitable range and the sward quality is maintained.