Potential of several native and introduced warm season grasses as components of Silvopastures in the Southeastern United States

The goal of this study was to evaluate growth and nutritional characteristics of seven warm season grasses, including several natives, produced under simulated partial shading (50%) typical of loblolly pine silvopastoral systems in the southeastern United States. Forages included ‘Tifton 9’ bahiagrass (Paspalum notatum), ‘Tifton 85’ bermudagrass (Cynodon dactylon), ‘Alamo’ switchgrass (Panicum virgatum), ‘Kaw’ Big Bluestem (Andropogon gerardii), ‘Americus’ Indiangrass (Sorghastrum nutans), ‘Harrison’ Florida paspalum (Paspalum floridanum), and Nacogdoches Eastern gamagrass (Tripsacum dactyloides). Shade affected several quality parameters, including crude protein (CP) (p?<?0.0001), acid detergent fiber (ADF) (p?=?0.0413), in vitro true digestibility (IVTD) (p?<?0.0001), and total digestible nutrients (TDN) (p?=?0.0132). Shade affected the parameters differently depending on forage type, but generally improved quality by increasing CP, IVTD, and TDN; however, shade significantly increased ADF (p?=?0.0413), though the magnitude was small (344.2 vs. 351.1 g kg^?1), and increases were isolated to big bluestem and bahiagrass. Shade reduced dry matter yield (DMY) (p?<?0.0001), and there were differences among forage species (p?<?0.0001). Bahiagrass and Florida paspalum showed the highest yields, regardless of shade treatment. Gamagrass and Florida paspalum would likely have performed better if harvested by days of rest, instead of by height. These could be viable forage species to a silvopasture system, but further studies should be conducted. Based on overall quality and yield, potential beef cattle gains, and persistence under intensive defoliation, the best forage was bahiagrass (introduced), and the best selections for native grasses were switchgrass and Indiangrass. These results indicate that there is potential for several warm season forages, including native grasses, to maintain productivity and quality under shade, which would increase the site-specific options for forage selections in this system.

     

Temporal and spatial patterns of denitrification enzyme activity and nitrous oxide fluxes in three adjacent vegetated riparian buffer zones

The aim of this study was to investigate temporal and spatial patterns of denitrification enzyme activity (DEA) and nitrous oxide (N₂O) fluxes in three adjacent riparian sites (mixed vegetation, forest and grass). The highest DEA was found in the surface (0–30 cm) soil and varied between 0.7±0.1 mg N kg^–1 day^–1 at 5°C and 5.9±0.4 mg N kg^–1 day^–1 at 15°C. There was no significant difference (P >0.05) between the DEA in the uppermost (0–30 cm and 60–90 cm) soil depths under different vegetation covers. In the two deepest (120–150 cm and 180–210 cm) soil depths the DEA varied between 0.0±0.0 mg N kg^–1 day^–1 at 5°C and 4.4±0.9 mg N kg^–1 day^–1 at 15°C and was clearly associated with the accumulation of buried organic carbon (OC). Two threshold values of OC were observed before DEA started to increase significantly, namely 5 and 25 g OC kg^–1 soil at 10–15°C and 5°C, respectively. In the three riparian sites N₂O fluxes varied between a net N₂O uptake of –0.6±0.4 mg N₂O-N m^–2 day^–1 and a net N₂O emission of 2.5±0.3 mg N₂O-N m^–2 day^–1. The observed N₂O emission did not lead to an important pollution swapping (from water pollution to greenhouse gas emission). Especially in the mixed vegetation and forest riparian site highest N₂O fluxes were observed upslope of the riparian site. The N₂O fluxes showed no clear temporal trend.     

Markers of feline leukaemia virus infection or exposure in cats from a region of low seroprevalence

Molecular techniques have demonstrated that cats may harbour feline leukaemia virus (FeLV) provirus in the absence of antigenaemia. Using quantitative real-time polymerase chain reaction (qPCR), p27 enzyme-linked immunosorbent assay (ELISA), anti-feline oncornavirus-associated cell-membrane-antigen (FOCMA) antibody testing and virus isolation (VI) we investigated three groups of cats. Among cats with cytopenias or lymphoma, 2/75 were transiently positive for provirus and anti-FOCMA antibodies were the only evidence of exposure in another. In 169 young, healthy cats, all tests were negative. In contrast, 3/4 cats from a closed household where FeLV was confirmed by isolation, had evidence of infection. Our results support a role for factors other than FeLV in the pathogenesis of cytopenias and lymphoma. There was no evidence of exposure in young cats. In regions of low prevalence, where the positive predictive value of antigen testing is low, qPCR may assist with diagnosis.     

Atrazine hydrolysis. Part I: Proton catalysis at 25°C

Six new results have been obtained in an investigation of the catalysed hydrolysis of atrazine. A procedure was developed for determining rate constants from the first 20 mol% of the reaction. The reduced length of the experiments increased the experimental productivity and minimised the risk of sample deterioration. The proton catalysis rate was measured at 25°C, over the H⁺ concentration range of 1 to 10 mmol litre^?1. This shortened the extrapolation to the pH values of field conditions, and guaranteed the absence of doubly-protonated atrazine. Because spectrophotometry has been regarded as a controversial method for studying the hydrolysis kinetics of the 1,3,5-triazine herbicides, this method was re-examined. Excellent agreement was obtained from a comparison of the gas-liquid chromatographic and spectrophotometric methods of monitoring the kinetics experiments. Of the widely diverging relationships found in the literature for the extrapolation of laboratory half-lives to the pH range of field conditions, the one deduced from the reaction scheme of Plust et al. was found to be theoretically correct. Its parameters have been calibrated with several hundred experimental measurements. The proton is not the dominant catalytic agent in soils, but its calibration is essential for identifying those catalytic agents that are dominant. It has been deduced that the temperature dependence of the experimental rate constant is governed by the temperature responses of two parameters.     

Swine infection with Trichinella spiralis: Comparative analysis of the mucosal intestinal and systemic immune responses

The immune protective response developed by swine against Trichinella spiralis is not yet fully understood, particularly at the mucosal level. This study aimed to characterise intestinal immunity to T. spiralis by comparison with the systemic response in specifically pathogen-free pigs. For this purpose, the kinetics of cytokine and antibody production were assessed in the intestinal mucosa and serum of swine infected with T. spiralis for up to 60 days post-infection (dpi). An ex vivo model of jejunum mucosa culture was used to collect the supernatant as a source of antibodies (Abs). Mucosal antibodies were observed by Western blot from 15 dpi, while serum antibodies were expressed from 20 dpi. Both sources of antibodies initially recognized a 110 kDa protein, followed by the identification of 35, 43/46 and 55/59 kDa proteins. IgG1 and IgA antibodies were strongly expressed within the mucosa. The expression levels of Type 1 (IFN-gamma, IL-12), Type 2 (IL-4, IL-6), pro-inflammatory (TNF-alpha) and regulatory (IL-10, TGF-beta) cytokines were assessed by RT-PCR in the intestinal mucosa and spleen. Both IL-10 and IFN-gamma mRNA levels were increased in mucosa, whereas IL-6 and IL-12 mRNA were expressed in spleen. Taken together, these results demonstrated a mixed Type 1/Type 2 profile, the Type 2 profile being dominant in the mucosa.     

Induction of enhanced CH4 oxidation in soils: NH4 inhibition patterns

The influence of NH₄⁺ on microbial CH₄ oxidation is still poorly understood. Therefore, the influence of NH₄Cl and (NH₄)₂SO₄ on CH₄ oxidation was studied in soils at the different stages of the induction of enhanced methanotrophic activity. After a brief peak in the methanotrophic activity, a steady state was observed in which NH₄⁺ inhibited CH₄ oxidation at low CH₄ concentrations, and stimulated CH₄ oxidation at high concentrations. Chloride did not strongly inhibit CH₄ oxidation during this phase. During a second phase methanotrophic activity increased again. Ammonium no longer stimulated CH₄ oxidation, and Cl⁻ became an important source of uncompetitive inhibition. It was hypothesized that type I methanotrophs dominated during the first, soil-N-dependent phase while N₂-fixing type II methanotrophs dominated the second, soil-N-independent phase.     

Microbial Activity of Cu Contaminated Soils and Effect of Lime and Compost on Soil Resiliency

In vineyards, the long-term use of copper fungicides has increased soil Cu concentrations that can adversely affect the number and activities of soil microorganisms. To better understand this phenomenon and to ameliorate such harmful effects, an incubation experiment was carried out with a sandy loam and a sandy soil to which increasing rates of CuSO₄ were added. By this treatment, the basal soil respiration (7-55%) and decomposition of added vine branches (46-86%) was inhibited. At the application rate of 500 mg Cu kg^?1, soil microbial biomass-C was inhibited (7-66%) in the sandy soil and stimulated (2-10%) in the sandy loam soil. The specific respiration rate was a reliable indicator for Cu stress, and it increased with time and higher Cu concentrations before lime and compost applications. Total number of bacteria and streptomycetes were also strongly inhibited. Fungal population was significantly more tolerant to copper toxicity than the bacteria. A stimulation of fungal population at a dose of 500 mg Cu kg^?1 in both soils was observed. A criterion such as “stimulation” lasting for more than 60 days can also be used as indication of Cu contamination of soils. The order of inhibition (on day 125) at a dose of 500 mg Cu kg^?1 soil was as follows: A. sandy loam soil (pH> 7.0) — fungi < biomass-C < basal soil respiration < bacteria < streptomycetes; B. sandy soil (pH< 6.0) — fungi < basal soil respiration < biomass-C < bacteria < streptomycetes. The application of lime increased soil recovering ability at a moderate rate (for CO₂ production – 22-70% and for biomass-C- 39-156%), but the combination of lime and compost significantly increased soil resiliency (for CO₂ production- 16-518% and for biomass-C- 103-693%). The soil resiliency assessed by number of bacteria in compost treatments was 30-120% in sandy loam soil and 92-700% in the sandy soil. Compost and lime application increased the number of streptomycetes from 52 to 500% in sandy loam soil and from 100 to 700% in sandy loam soil. Fungal population was less increased in sandy soil as compared to sandy loam soil. The ecological dose higher than 5% inhibition of microbial processes and microorganisms appears to be suitable to assess Cu contamination of soils. CO₂ production, biomass-C and specific respiration rate were less sensitive indicators as compared to streptomycetes and bacteria. It appears that compost application effectively promoted the recovery of soil microbial activity and soil fertility of Cu contaminated soils.     

Farmers’ perceptions of coexistence between agriculture and a large scale coal seam gas development

The Coal Seam Gas (CSG) extraction industry is developing rapidly within the Surat Basin in southern Queensland, Australia, with licenses already approved for tenements covering more than 24,000 km². Much of this land is used for a broad range of agricultural purposes and the need for coexistence between the farm and gas industries has been the source of much conflict. Whilst much research has been undertaken into the environmental and economic impacts of CSG, little research has looked into the issues of coexistence between farmers and the CSG industry in the shared space that is a farm business, a home and a resource extraction network. We conducted three workshops with farmers from across a broad region undergoing CSG development to explore farmers’ perceptions of some of the issues arising from large scale land use change. Workshops explored the importance of place identity and landscape aesthetics for farmers, farmers’ acceptance and coping with change, and possible benefits from off-farm income. We found that farmers believed that place identity was not well understood by CSG staff from non-rural backgrounds and that farmers struggled to explain some concerns because of the different way they interpreted their landscape. Furthermore, high staff turnover, and the extensive use of contractors also impacted on communications. These factors were the cause of much frustration and farmers felt that this has led to severe impacts on mental health and wellbeing. Farmers felt that a change in culture within the CSG companies will be required if engagement with farmers is to improve and that efforts to employ local people in these communications was helping this. The workshops also identified a range of issues perceived by farmers arising from increased traffic volumes, impacts to mental health and wellbeing, place identity and loss of water resources for farmers. Finally, it was suggested that scientists and agricultural industry groups will need to work closely with farmers to develop understanding of these emerging issues and to develop solutions that are timely and relevant.     

Soil organic carbon–stock changes in Flemish grassland soils from 1990 to 2000

Total soil organic‐carbon (SOC) stocks for grassland soils in Flanders (N Belgium) were determined for the Kyoto Protocol reference year 1990 and 2000 in order to investigate whether these soils have been CO₂ sinks or sources during that period. The stocks were calculated by means of detailed SOC datasets, which were available at the community scale for the whole of Flanders. The total SOC stocks for Flemish grassland soils (1 m depth) were estimated at 38 Mt SOC in 1990 and 34 Mt SOC in 2000. The loss of SOC resulted from a decrease in the SOC content of grassland soils (71%) and could also partly (29%) be explained by a decline in grassland area. Significant decreases in %SOC for the 0–6 cm depth layer were found for the 1990s for the coarser‐textured soils with SOC losses ranging between –0.3% and –0.5% over the 10 y period. Specific management practices that disturb the SOC balance such as conversion to temporary grassland and a reduction of animal‐manure application are hypothesized to have contributed to the observed loss of SOC stocks. We furthermore conducted an analysis of uncertainty of the 1990 and 2000 grassland SOC–stocks calculation using Monte Carlo analysis. Probability‐distribution functions were determined for each of the inputs of the SOC‐stock calculation, enabling us to assess the uncertainty on the 1990 and 2000 SOC stocks. The frequency distributions of these simulated stocks both closely approached lognormal distributions, and their 95%‐confidence intervals ranged between 150% and 50% of the calculated mean SOC stock. The standard error on the measured decrease in SOC stocks in Flemish grassland soils during the 1990s was calculated to be 7–8 Tg SOC, which is equivalent to twice this decrease. This clearly shows that large‐scale changes in SOC stocks are uncertainty‐ridden, even when they are based on detailed datasets.