硫杆菌以及好养异养型硫氧化菌对元素硫的氧化

The prediction of the oxidation rate of elemental sulfur (S⁰) is a critical step in sulfur (S) fertilizer strategy to supply plant-available sulfur. An incubation experiment was conducted to determine the rate and amount of S⁰ oxidation in relation to the contribution of Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria. After 84 days, 16.3% and 22.4% of the total S⁰ applied to the soil were oxidized at 20 and 30 ℃, respectively. The oxidation of S⁰ proved to be a two-step process with a rapid oxidation during the first 28 days and a slow oxidation from then on. The highest oxidation rate of 12.8 μg S cm^-2 d^-1 was measured during the first two weeks at 30 ℃. At 20 ℃ the highest oxidation rate of 10.2 μg S cm^-2 d^-1 was obtained from two to four weeks after start of the experiment. On an average the soil pH declined by 3.6 and 4.0 units after two weeks of experiment. At the same time the electric conductivity increased nine times. With the oxidation of S⁰ the population of Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria increased. The corresponding values for Thiobacillus spp. and aerobic heterotrophic S-oxidizing bacteria increased from 2.9 × 10⁵ and 1.4 × 10⁵ g^-1 soil at the start of the experiment to 4 × 10⁸ and 5.6 × 10⁸ g^-1 soil 14 days after S⁰ application, respectively. No Thiobacillus spp. was present eight weeks after S⁰ application. The results suggested that oxidation of residual S⁰ completely relied on aerobic heterotrophic S-oxidizing bacteria.     

REINTEGRATION OF CROP-LIVESTOCK SYSTEMS IN EUROPE: AN OVERVIEW

• ICLS combines the benefits of specialization with increased resilience of the system.• Clear opportunities but also barriers for ICLS were observed.• ICLS need to be embedded within future environmental legislation.• ICLS systems with a range of intensities are needed to support a biodiverse landscape.Ongoing specialization of crop and livestock systems provides socioeconomic benefits to the farmer but has led to greater externalization of environmental costs when compared to mixed farming systems. Better integration of crop and livestock systems offers great potential to rebalance the economic and environmental trade-offs in both systems. The aims of this study were to analyze changes in farm structure and review and evaluate the potential for reintegrating specialized intensive crop and livestock systems, with specific emphasis on identifying the co-benefits and barriers to reintegration. Historically, animals were essential to recycle nutrients in the farming system but this became less important with the availability of synthetic fertilisers. Although mixed farm systems can be economically attractive, benefits of scale combined with socio-economic factors have resulted in on-farm and regional specialization with negative environmental impacts. Reintegration is therefore needed to reduce nutrient surpluses at farm, regional and national levels, and to improve soil quality in intensive cropping systems. Reintegration offers practical and cost-effective options to widen crop rotations and promotes the use of organic inputs and associated benefits, reducing dependency on synthetic fertilisers, biocides and manure processing costs. Circular agriculture goes beyond manure management and requires adaptation of both food production and consumption patterns, matching local capacity to produce with food demand. Consequently, feed transport, greenhouse gas emissions, nutrient surpluses and nutrient losses to the environment can be reduced. It is concluded that reintegration of specialized farms within a region can provide benefits to farmers but may also lead to further intensification of land use. New approaches within a food system context offer alternatives for reintegration, but require strong policy incentives which show clear, tangible and lasting benefits for farmers, the environment and the wider community.     

Efficacy of metaphylactic florfenicol therapy during natural outbreaks of bovine respiratory disease

The efficacy of an injectable formulation of florfenicol (300 mg/mL) as metaphylactic control of naturally occurring bovine respiratory disease (BRD) was evaluated in two double‐blind randomly controlled field studies on two Dutch veal calf herds (A and B). Cattle aged not older than 3 months and in the direct presence of calves with clinical respiratory disease were randomly allocated to treatment with 40 mg/kg florfenicol subcutaneously (s.c.) a positive control treatment (12.5 mg/kg tilmicosin p.o. twice daily for five consecutive days in herd A, and 12.5 mg/kg doxycycline p.o. twice daily for five consecutive days in herd B), or a negative control (one placebo saline s.c. administration on D0). The predominant respiratory pathogens present in pretreatment respiratory samples from affected animals were Mycoplasma bovis and Pasteurella multocida in outbreaks A and B, respectively. Metaphylactic administration of florfenicol resulted in a statistically significant weight gain, decreased rectal temperature for five consecutive days after treatment and decreased metaphylactic failure percentages compared with both positive and negative control groups. In summary, these studies demonstrated that a single s.c. injection of florfenicol is effective and practical for control of the bacterial component of BRD in veal calves.     

Seed production of Raphanus raphanistrum following herbicide application during reproduction and effects on wheat yield

The influence of weather and agronomic factors on the activity of six selective herbicides applied at reproductive stages of development for the reduction in seed production of Raphanus raphanistrum in wheat was evaluated. The herbicides used in this way generally reduced seed production by between 80% and 100%. Triasulfuron and mixtures of triasulfuron + MCPA consistently provided the greatest reduction in seed production. This was greater when herbicides were applied at the bud and early flowering stages of R. raphanistrum and the efficacy of the herbicides increased as maximum temperature on the day of spraying increased over the range 14–24°C. An applied model developed from these results predicts the reduction in seed production of R. raphanistrum, for each herbicide, given the stage of weed development and maximum temperature on the day of its application. Wheat yield was significantly reduced as densities of R. raphanistrum increased, with predicted losses at low densities being approximately half of those reported in the literature. There was no consistent evidence that the late application of herbicides had any negative effect on wheat yield through crop injury, nor was there any indication of yield improvement. It is concluded that certain herbicides applied during the reproductive phase of development have considerable potential to reduce R. raphanistrum seed production in wheat crops. As part of an integrated strategy, such late post‐emergence application of selective herbicides to regulate seed production has a likely role for managing weed seedbanks, but little or no value for counteracting weed competition.