The influence of the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) on the mineralization of litter-derived alkanes and the abundance of the alkane monooxygenase gene (alkB) in the detritusphere of Pisum sativum (L.)

In the present study, the temporal and spatial variation of the abundance of the alkane monooxygenase gene alkB and 16S rRNA genes in different soil compartments was analysed in the presence or absence of 2-methyl-4-chlorophenoxyacetic acid (MCPA) after the addition of pea litter to soil in a microcosm study. Samples were analysed shortly after litter addition (T0) and 1?week (T1), 3?weeks (T3) and 6?weeks (T6) after the addition of litter. In addition also, the quantity and quality of litter-derived alkanes was analysed and measured. The results revealed a fast and complete degradation of MCPA in all compartments throughout the experiment. Nevertheless, significant changes in the distribution patterns of short- and middle-chained alkanes suggest an interaction of MCPA and alkane degradation. alkB gene copy numbers were highly influenced by the time point of analysis and by the investigated soil compartment. Overall, an increase in alkB gene copy numbers from T0 to T3 was visible in the upper soil compartments whereas a decrease compared to T0 was measured in the deeper soil compartments. MCPA addition resulted in an increase of alkB abundance at T6. Gene copy numbers of 16S rRNA were not influenced by sampling time and soil compartment. In contrast to the control treatments, a slight increase in 16S rRNA gene copy numbers was visible at T1 and T3 compared to T0 in all soil compartments.     

Does the “high sugar” trait of perennial ryegrass cultivars express under temperate climate conditions?

The objective was to evaluate water‐soluble carbohydrate (WSC) and crude protein (CP) concentration of perennial ryegrass (PRG) cultivars with different genetic potential for producing WSC under two contrasting agronomic managements in temperate climate (southern Chile). A 4 × 2 factorial design was randomly allocated to 24 plots (31 m² each, three blocks): four PRG cultivars (diploid standard cultivar, “2nSt”; tetraploid standard cultivar, “4nSt”; diploid high sugar cultivar developed in New Zealand, “2nHSNZ”; and tetraploid high sugar cultivar developed in Europe, “4nHSEU”) and two agronomic managements (“favourable,” defoliations at three leaves per tiller and nitrogen (N) fertilization rate of 83.3 kg N ha^?1 year^?1; “unfavourable,” defoliations at two leaves per tiller and N fertilization rate of 250 kg N ha^?1 year^?1). Herbage samples were collected in early spring, spring, summer and autumn. Concentration of WSC did not differ among cultivars in spring and summer, averaging 194 and 251 g/kg DM, respectively. The cultivar 4nHSEU had the greatest WSC concentration in early spring and autumn (187 and 266 g/kg DM, respectively) and the greatest CP concentration across samplings (average 230 g/kg DM). Favourable management improved WSC concentrations in early spring and summer and decreased CP in spring, summer and autumn. Annual DM yield did not vary with cultivar or management, averaging 8.43 t/ha. Within a 12‐month study at one site in a temperate environment in southern Chile, PRG cultivars have not shown a consistent expression of the “high sugar” trait, where a genetic × environment interaction might be operating.     

Exhaustive Screening of Long-Term Pollutants in Riverbank Sediments of the Wurm River,Germany

Fluvial sediments can act as archives for long-term pollution. However, in environmental studies, often only preselected contaminants and, therefore, only a limited part of the pollution are considered. Herein, geochemical investigations of riverbank samples of the Wurm River (catchment <?400 km²) depict the anthropogenic impact of the city Aachen (250,000 inhabitants) to its main outlet resulting in an exhaustive list of present pollutants including their concentrations. The study is based on 14 riverbank sediment samples at eight sampling sites on a 7.6-km-long segment of the Wurm River. The sediment samples were analyzed for grain size composition (laser diffraction particle size analyzer), total organic carbon (TOC), trace element inventory (X-ray fluorescence), and organic compounds (chromatography-mass spectrometry). Here, we report quantitative data for 71 persistent organic substances as well as six trace elements (Cu, Zn, As, Ba, Hg, and Pb) entering the Wurm River due to domestic and industrial emissions. In general, a slight decline of, e.g., PTEs, DDX, and PCB concentrations with decreasing sampling depth points to a steady improvement of conditions. Whereas no clear trends can be seen for organic pollutants along the investigated reach with increasing distance to the main source of pollution (Aachen city). As obtained concentrations for organic pollutants indicate a rather low level of pollution, trace element values exceed geogenic background values by far. Furthermore, we used selected compounds as time markers for a rough estimation of sedimentation rates. Obtained values point to a highly complex morphodynamic regime with changing sedimentation rates (0.6 to 3.0 cm a^?1) within barely 100 m of river course.     

The accumulation of phytolith-occluded carbon in soils of different grasslands

Purpose

A better understanding of the role of grassland systems in producing and storing phytolith-occluded carbon (PhytOC) will provide crucial information in addressing global climate change caused by a rapid increase in the atmospheric CO₂ concentration.

Materials and methods

Soil samples of typical steppe, meadow steppe, and meadow in Inner Mongolia, China, were taken at 0–10-, 10–20-, 20–40-, and 40–60-cm depths in July and August of 2015. The soil phytoliths were isolated by heavy liquid (ZnBr₂), and the soil PhytOC was determined by the traditional potassium dichromate method.

Results and discussion

The results of our study showed that the storage of soil phytoliths was significantly higher in the meadow (33.44 ± 0.91 t ha^?1) cf. meadow steppe (26.8 ± 0.98 t ha^?1) and typical steppe (21.19 ± 4.91 t ha^?1), which were not different. The soil PhytOC storage was significantly different among grassland types, being: meadow (0.39 ± 0.01 t ha^?1) > meadow steppe (0.29 ± 0.02 t ha^?1) > typical steppe (0.23 ± 0.02 t ha^?1). PhytOC storage in typical steppe soil within the 0–60-cm soil layer is the lowest and that in meadow soils is the highest. The grassland type and the soil condition play significant roles in accumulation of phytoliths and PhytOC in different grassland soils. We suggest that the aboveground net primary productivity (ANPP) is important in soil phytolith accumulation and PhytOC content.

Conclusions

Phytolith and PhytOC storages in grassland soil are influenced by factors such as grass type, local climate and soil conditions, and management practices. Management practices to increase grass biomass production can significantly enhance phytolith C sequestration.

     

Wheat straw biochar application increases ammonia volatilization from an urban compacted soil giving a short-term reduction in fertilizer nitrogen use efficiency

Journal of Soils and Sediments - The potential for using biochar to reclaim degraded urban land into productive land needs to be verified to address the incipient loss of agricultural land. A pot...     

Plant growth responses to biochar addition: an Australian soils perspective

The use of biochar as an agricultural amendment has attracted much attention owing to its potential to improve soil condition and plant growth; however, production outcomes are often uncertain. Although soil type is a major driver of plant productivity, there are relatively few biochar studies that directly compare plant growth responses across a range of soil types. We tested the wheat growth response to biochar derived from poultry litter and from wheat straw applied at 1, 5 and 10 t ha^?1 (approximately 0.13, 0.67 and 1.33 % w/w) in four soils representing major agricultural regions in Australia: an acidic arenosol (Western Australian cereal belt), an acidic rhodic ferralsol (Northern New South Wales), a neutral vertisol (Queensland cropping) and an alkaline haplic calcisol (Eyre Peninsula in South Australia). In the neutral vertisol, where plant growth was vigorous in the control treatments, biochar had little impact, whereas in the alkaline calcisol, there was a small significant increase in shoot biomass at high (10 t ha^?1) application rates. Plant growth responses in the acidic soils were most evident but demonstrated a strong contrast to one another. In the acidic arenosol, negative growth impact correlated with increasing electrical conductivity, while in the acidic ferralsol a small rate-dependent increase in pH correlated with relatively large gains in biomass, possibly due to improved phosphorus nutrition and alleviated Al toxicity. Moving towards effective integration of biochar as a management tool will not only require stratification based on soil types, but wider consideration of the main plant production constraints, such as pH, pertinent to a particular system.     

Detection of a Theileria species in dogs in South Africa

A Theileria species was detected by PCR in blood samples collected from dogs in the Pietermaritzburg area and was also found in dogs presented at the Outpatients Clinic of the Onderstepoort Veterinary Academic Hospital (OVAH), in the Pretoria area, South Africa. In the Pietermaritzburg area, 79 of the 192 samples were positive, while 3 out of 1137 of the Onderstepoort samples were positive. Three positive samples from Pietermaritzburg were co-infected with Ehrlichia canis. PCR positive samples were further analysed by the Reverse Line Blot (RLB) and sequence analysis. Phylogenetic analysis of the 18S rRNA full-length gene sequences of one sample (VT12) from Pietermaritzburg and two samples from OVAH (BC281 and BC295) revealed a close relationship with sequences of Theileria species (sable). Clinical signs of the dogs that were examined at Pietermaritzburg and OVAH included an immune-mediated condition with severe thrombocytopenia. These findings identify a Theileria sp. in dogs for the first time in South Africa and add yet another microorganism to the growing list of haemoprotozoan parasites infecting dogs worldwide. The clinical significance of this infection in dogs is poorly resolved.