Soil properties influencing the denitrification potential of Flemish agricultural soils

The denitrification potential of the soil horizons between 0- and 90-cm depth of 20 agricultural fields, representative of the most frequent combinations of agricultural crops and soil textures in Flanders (Belgium), and the factors affecting the denitrification potential were studied in the laboratory under controlled conditions. The denitrification potential in the presence of an added soluble C and N source was measured at 15°C after saturation of air-dried soil samples with water. The denitrification potential of the lower horizons was generally negligible compared to the upper horizons. The lower denitrification potential of the deeper horizons could partially be explained by their limited C availability. The denitrification potential of the upper horizons strongly depended on texture. Based on this parameter the soils could be divided into three groups: soils with a high clay content (>30% clay) were characterised by a high denitrification potential (>8.33 µg N g^-1 dry soil day^-1); soils with medium texture had a medium denitrification potential, between 0.41 and 7.25 µg N g^-1 dry soil day^-1; and soils with a high sand content (>80% sand) had a low denitrification potential (<2.58 µg N g^-1 dry soil day^-1). In most cases, extending the saturation period during pre-incubation increased the denitrification potential. Comparison of the denitrification potential of the upper horizons with and without addition of a soluble C source showed that the denitrification potential of the upper horizons of these soils was limited by their percentage of endogenous C. The measured denitrification potentials indicate that denitrification losses in soils high in clay content can be important when NO₃ ^- concentrations are high.     

Seasonal effect of the exotic invasive plant Solidago gigantea on soil pH and P fractions

Invasions by alien plants can alter biogeochemical cycles in recipient ecosystems. We test if Early Goldenrod (Solidago gigantea) alters P fractions. To that end, we compare invaded plots and adjacent, uninvaded resident vegetation for specific fractions of organic and inorganic P, phosphomonoesterase (PME) activity in topsoil, and immobilization of P in above‐ and belowground organs and in soil microbial biomass. Invaded plots had lower soil pH and 20%–30% higher labile P fractions (resin‐P_i, bicarb‐P_i, NaOH‐Pi), and the difference was consistent across seasons. There was no difference in microbial P. Alkaline‐PME activity was 30% lower in topsoil of invaded plots. Annual P uptake in aboveground phytomass was not markedly higher in Solidago. In contrast, P in belowground organs steadily increased in autumn in invaded plots, due to both increased biomass and increased P concentrations. This indicated higher net P immobilization in Solidago, far in excess of both resorption from senescing shoots and P requirements for aboveground biomass in subsequent year. Higher turnover rates of P in belowground organs and mobilization of sparingly soluble P forms through rhizosphere acidification may be involved in the observed differences in soil P status between invaded and uninvaded plots.     

Impact of residue characteristics on phosphorus availability in West African moist savanna soils

The role of residue characteristics in enhancing the availability of P was investigated in a greenhouse study using two soils from the northern Guinea savanna (NGS) and four from the derived savanna (DS) zones of the West African moist savanna. Eight organic residues of varying C-to-P ratio were used and maize ( Zea mays) was grown for 7 weeks. The effect of the organic residues on P availability (measured as resin P and maize P accumulation) differed among the soils. On average, the increase in resin P, calculated as {[(soil+residue)–control]/(control)×100}, was between 8% (Davié, DS) and 355% (Danayamaka, NGS). Maize P accumulation was increased by ca. 11% in Davié and Niaouli (DS) soils and 600% in Danayamaka soil. The increase in maize total dry matter yield (DMY) ranged from 2% to 649%. Residues with C-to-P ratio >200 produced lower DMY than those with lower ratios. Residue organic P (Po) extractable with 0.2 N H₂SO₄ (acid-Po) accounted for 92% ( P =0.0001) of the variation in DMY in a step-wise regression with residue parameters as independent variables and mean DMY as the dependent variable. The residue Po extractable with 0.5 M NaHCO₃ (HCO₃-Po) correlated significantly with DMY in Danayamaka and Davié soils, and with P accumulation in Danayamaka soil. The relationships between the residue Po and DMY might imply that Po fractions in decomposing residues contribute to P availability. However, the suitability of using the Po content of organic residues to predict their agronomic value with respect to P nutrition needs further evaluation.     

Microbial Activity Indices： Sensitive Soil Quality Indicators for Trace Metal Stress

Physicochemical properties, total and DTPA （diethylenetriaminepentaacetic acid）-extractable Cu, Zn, Pb and Cd contents, microbial biomass carbon （C） content and the organic C mineralization rate of the soils in a long-term trace metal-contaminated paddy region of Guangdong, China were determined to assess the sensitivity of microbial indices to moderately metal-contaminated paddy soils. The mean contents of total Cu, Zn, Pb and Cd were 251, 250, 171, and 2.4 mg kg^-1 respectively. DTPA-extractable metals were correlated positively and significantly with total metals, CEC, and organic C （except for DTPA-extractable Cd）, while they were negatively and highly significantly correlated with pH, totall Fe and Mn. Metal stress resulted in relatively low ratios of microbial biomass C to organic C and in remarkable inhibition of the microbial metabolic quotient and C mineralization rate, which eventually led to increases in soil organic C and C/N. Moreover, microbial respiratory activity showed a stronger correlation to DTPA-extractable metals than to total metal content. Likewise, in the acid paddy soils some “linked” microbial activity indices, such as metabolic quotient and ratios of basal respiration to organic C, especially during initial incubation, were found to be more sensitive indicators of soil trace metal contamination than microbial biomass C or basal respiration alone.     

Boreal forest microbial community after long-term field exposure to acid and metal pollution and its potential remediation by using wood ash

A 2²-factorial design with sulphuric acid (pH 3.1) and Cu-Ni addition was used to assess the effects of moderate amounts of continuous acid (Acid and CuNi+Acid) and metal (CuNi and CuNi+Acid) deposition on humus microbial activity and community structure in the field after nine growing seasons. These 20 field experiment samples were also used to measure the suitability of wood ash for remediation. Microcosms were treated with wood ash at a fertilization rate of 5000 kg ha⁻¹, irrigated with water and incubated for 2 months in the dark at 20 °C and a constant relative humidity of 60%. Microcosms only irrigated with water served as a control. Microbial activity was measured as basal respiration. Microbial community structure was determined by phospholipid fatty acid analysis, which mainly targets bacteria. Fungal community structure was assessed by 18S rDNA-targeted polymerase chain reaction-denaturing gradient gel electrophoresis analysis. The bioavailability of Cu was tested with the Pseudomonas fluorescens DF57-Cu15 reporter strain, which bioluminescences in the presence of Cu. Our field study showed, that acid and metal treatments both changed the humus layer microbial community structure. Acid application decreased humus layer pH and base saturation (BS) and increased the amounts of both extractable and bioavailable Cu. Metal application increased the concentration of extractable Ni and changed the fungal community structure. In irrigated laboratory microcosms the above-mentioned treatment effects were still seen except for the acid and metal effects on microbial and fungal community structures. For ash-treated microcosms, neither acid nor metal effects were found for humus layer pH, BS, extractable Cu and Ni, or bioavailable Cu. Thus, wood ash can be used for remediation of acid and metal polluted humus.     

利用15NO3-标记法研究土壤微生物量氮的化学及生物有效性

采用加入含15N的硝态氮培养方法标记了土壤微生物量氮 ,然后利用碱解扩散法测定了标记土壤有效氮含量 ,温室培养法评价了小麦对标记的土壤微生物量氮的吸收情况。结果表明 ,碱解扩散法对土壤微生物量固持的15N的提取比率 (即提取液中15N原子百分超 /土壤15N原子百分超 )在 1 47～ 2 83之间(平均 2 0 1 ) ,碱解氮中约有 3 0 1 %～ 61 6% (平均 42 9% )来自土壤微生物固持氮。植物体15N丰度在0 749%～ 1 1 62 %之间 ,明显高于15N的自然丰度 ,表明土壤微生物固持的15N在小麦生长期间发生释放 ,为植物利用。土壤微生物固持氮对植物的有效性比率 (植物地上部分15N原子百分超 /土壤15N原子百分超 )在 3 7～ 7 1之间。可见 ,土壤微生物量固持氮有较高的化学及生物有效性     

酸性土壤磷分级新方法建立与生物学评价

土壤磷分级方法可用于估算土壤有效磷数量、不同土壤磷组分库数量及其对土壤有效磷的补充能力。以云南赤红壤、黄红壤及湖北棕红壤为供试材料,运用张守敬方法、蒋柏藩方法及本文提出的新方法,对三种酸性土壤和其石灰改良后的土壤磷进行分级研究,探讨石灰改良对酸性土壤磷组分数量及其生物有效性的影响。结果表明:Ca2-P、Al-P和Fe-P是酸性土壤主要的有效磷源,O-P(闭蓄态磷)也是潜在有效磷源,土壤中活性有机磷库相对比较稳定,可转化为高活性有效磷源供植物吸收利用。与两种经典磷分级方法相比,新方法将O-P划分为O-Al-P和O-Fe-P,O-Fe-P较好地反映了石灰处理与对照之间的土壤磷植物有效性差异。     

Pharmacokinetics of a high-concentration formulation of buprenorphine (Simbadol) in male dogs

ObjectiveTo describe the pharmacokinetics of buprenorphine in dogs following administration of a high-concentration formulation of buprenorphine.Study designProspective, randomized, crossover study.AnimalsA total of six healthy male intact Beagle dogs, aged 9–13 months and weighing 10.3 ± 1.4 kg (mean ± standard deviation).MethodsDogs were randomized to be administered buprenorphine (0.12 mg kg^–1; Simbadol, 1.8 mg mL^–1) via the intravenous (lateral saphenous) or subcutaneous (dorsal interscapular) route followed by the alternative route of administration after a 14 day interval. Blood was sampled before administration and at set times up to 72 hours after injection. Plasma buprenorphine concentration was measured using liquid chromatography–tandem mass spectrometry.ResultsA three-compartment model with zero or biphasic rapid and slow first-order input in (intravenous or subcutaneous data, respectively) and first-order elimination from the central compartment best fitted the data. The rapid first-order input accounted for 63% of the dosage absorption. Typical values (% interindividual variability) for the three compartment volumes were 900 (33), 2425 (not estimated) and 6360 (28) mL kg^–1. The metabolic and two distribution clearances were 25.7 (21), 107.5 (74) and 5.7 (61) mL minute^–1 kg^–1. The absorption half-life for the fast absorption phase was 8.9 minutes with a 0.7 (103) minute delay. The absorption half-life for the slow absorption phase was 347 minutes with a 226 (42) minute delay. Median (range) bioavailability calculated from noncompartmental analysis was 143 (80–239)%. Calculated terminal half-life was 963 minutes.Conclusions and clinical relevanceThe high-concentration formulation of buprenorphine administered subcutaneously had a large volume of distribution and a rapid absorption phase followed by slower, delayed absorption. The high estimate of bioavailability should be interpreted with caution as values above 100% are most commonly related to experimental issues.     

Dietary regimen of the woodpigeon (Columba palumbus)

Recently, new agricultural policies and European Directives brought to important changes in farming practice, some of which could affect food availability for the wild bird population endangering biodiversity. This study aims to evaluate the consequences of such agricultural changes in France on the woodpigeon's dietary regimen. A total of 1,093 woodpigeons were collected over a four-year period (2014–2017). Voluntary sampling was performed in six regions in the south-west of France by local hunters during this species’ autumnal migration and wintering. Ingluvies contents were recovered, macroscopically and microscopically identified, and then weighed before and after drying. Five food groups were identified: acorns, corn, green plant material, cultivated seeds and others. ANOVA testing followed by Tukey's test for multiple comparison were performed (R version 3.5.2). Significance was set at p < .05. A total of 762 woodpigeons met the study's inclusion criteria. Mean weight of total crop contents was less of 9 grams of dry matter. Most frequent food groups were “green plant material” (70.3%), acorns (42.3%) and corn (27.2%). In terms of grams of dry matter, the most important food in the crop content were acorns (62%): these were eaten more during the first two hunting seasons (p < .001), and in region A, lower amount was consumed compared to all other regions. On the contrary, corn intake peaked during the third year (p < .001), and in region A, birds had an increasing intake of this cereal. Cultivated seeds contributed to the diet more during migration (p = .007), while “green plant material” and others more during wintering (p = .011; p = .004). In conclusion, results confirm the opportunistic nature of the woodpigeon, balancing its diet according to food availability. Corn was eaten more in areas where the winter burying of chopped maize stover (mulching), provided by the Nitrate's directive, was in derogation.