Quantification of airborne N‐input in long‐term field experiments and its validation through measurements using 15N isotope dilution

The N‐deposition in Germany is commonly calculated as values of about 20—30 kg/ha·yr. This range is based on the measurements of the nitrate and ammonium nitrogen bulk deposition, which does not include the gaseous N‐deposition and the direct N‐uptake by plants. The calculation of airbone N‐deposition from N‐balances of the Static Fertilization Experiment Bad Lauchstädt came to 50—58 kg/ha·yr. This is consistent with results from other European long‐term experiments. Using the newly developed ¹⁵N‐based ITNI‐system, the total airborne N‐deposition can be determined. For Bad Lauchstädt analogous to results of former measuring periods an annual N‐deposition of 65 kg/ha·yr was measured in 1998, a figure greater than the balanced values. The balanced and measured values show, that airborne N‐deposition is often underestimated and amounts to at least 50 kg/ha·yr, which is a significant burden on natural ecosystems. By taking this extra N‐input into account in calculations for fertilizer recommendations in agriculture a decrease of N‐losses can be achieved which, in turn can also induce a decrease in airborne N‐deposition.     

Effect of maternal antibodies on induction and persistence of vaccine-induced immune responses against bovine viral diarrhea virus type II in young calves

OBJECTIVE: To determine the effect of maternally derived antibodies on induction of protective immune responses against bovine viral diarrhea virus (BVDV) type II in young calves vaccinated with a modified-live bovine viral diarrhea virus (BVDV) type I vaccine. DESIGN: Blinded controlled challenge study. ANIMALS: 24 neonatal Holstein and Holstein-cross calves that were deprived of maternal colostrum and fed pooled colostrum that contained a high concentration of (n = 6) or no (18) antibodies to BVDV. PROCEDURE: At 10 to 14 days of age, 6 seropositive and 6 seronegative calves were given a combination vaccine containing modified-live BVDV type I. All calves were kept in isolation for 4.5 months. Six calves of the remaining 12 untreated calves were vaccinated with the same combination vaccine at approximately 4 months of age. Three weeks later, all calves were challenged intranasally with a virulent BVDV type II. RESULTS: Seronegative unvaccinated calves and seropositive calves that were vaccinated at 2 weeks of age developed severe disease, and 4 calves in each of these groups required euthanasia. Seronegative calves that were vaccinated at 2 weeks or 4 months of age developed only mild or no clinical signs of disease. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that a single dose of a modified-live BVDV type-I vaccine given at 10 to 14 days of age can protect susceptible young calves from virulent BVDV type II infection for at least 4 months, but high concentrations of BVDV-specific maternally derived antibodies can block the induction of the response.     

Identification of patterns of transmission of Salmonella within swine production systems using pulsed field gel electrophoresis (PFGE) and repetitive sequence polymerase chain reaction (REP-PCR): a quantitative analysis

Pulsed field gel electrophoresis (PFGE) using 3 enzymes (Spe I, Xba I, Avr II) and repetitive sequence polymerase chain reaction (REP-PCR) with 3 primers (BOX, ERIC, REP) were compared with respect to their validity as a method for identifying transmission of Salmonella on swine farms. Sixty-eight isolates of Salmonella were obtained from feces of swine, cats, mice, and birds, insect body parts, water and floor samples, and boot scrapings collected on 9 swine farms in Illinois USA. Genetic distances between isolates were calculated using the Dice matching coefficient. Cluster analysis of distance matrices was conducted using the UPG-MA algorithm. There was no significant difference between PFGE and REP-PCR in the genetic diversity detected; however, REP-PCR differentiated between 14 pairs of isolates which PFGE identified as identical. There were no significant differences between PFGE and REP-PCR in identifying all or most close genetic links as isolates from the same farm, the same building, and from the same sampling visit, suggesting ecological validity for both methods. Thus, REP-PCR should be considered as an acceptable and perhaps preferable alternative to PFGE as a genotyping method for studies of Salmonella transmission.     

Effects of Free‐Air Carbon Dioxide Enrichment on Sap Flow and Canopy Microclimate of Maize Grown under Different Water Supply

The rise of atmospheric CO₂ concentration ([CO₂]) affects stomatal conductance and thus transpiration and leaf temperature. We evaluated the effect of elevated [CO₂] levels under different water supply on daily sap flow and canopy microclimate (air temperature (Tc) and vapour pressure deficit (VPD)) of maize. The crop was cultivated in circular field plots under ambient (AMB, 378 μmol mol^?1) and elevated [CO₂] (FACE, 550 μmol mol^?1) using free‐air CO₂ enrichment with sufficient water in 2007, while in 2008 a DRY semicircle received only half as much water as compared to the WET semicircle from mid of July. In 2007, sap flow was measured in WET simultaneously under AMB and FACE conditions and was significantly decreased by elevated [CO₂]. In 2008, sap flow was measured in all four treatments but not simultaneously. Therefore, data were correlated with potential evaporation and the slopes were used to determine treatment effects. Drought reduced whole‐plant transpiration by 50 % and 37 % as compared to WET conditions under AMB and FACE, respectively. Moreover, CO₂ enrichment did not affect sap flow under drought but decreased it under WET by 20 % averaged over both years. The saving of water in the period before the drought treatment resulted in a displacement of dry soil conditions under FACE as compared to AMB. Under WET, CO₂ enrichment always increased Tc and VPD during the day. Under DRY, FACE plots were warmer and drier most of the time in August, but cooler and damper short after the start of drought in July and from the end of August onwards. Thus, the CO₂ effect on transpiration under drought was variable and detectable rather easy by measuring canopy microclimate.     

Genome-wide insertional mutagenesis of Arabidopsis thaliana

Over 225,000 independent Agrobacterium transferred DNA (T-DNA) insertion events in the genome of the reference plant Arabidopsis thaliana have been created that represent near saturation of the gene space. The precise locations were determined for more than 88,000 T-DNA insertions, which resulted in the identification of mutations in more than 21,700 of the approximately 29,454 predicted Arabidopsis genes. Genome-wide analysis of the distribution of integration events revealed the existence of a large integration site bias at both the chromosome and gene levels. Insertion mutations were identified in genes that are regulated in response to the plant hormone ethylene.     

Volatiles from the 1994 Eruptions of Rabaul: Understanding Large Caldera Systems

The 1994 eruption of Rabaul, in Papua New Guinea, involved a small plinian eruption at Vulcan and a vulcanian eruption on the opposite side of the caldera at Tavurvur. Vulcan's ash leachates indicate seawater interaction that is consistent with earlier observations of low sulfur dioxide emissions and the presence of ice crystals in the initial plinian eruption cloud. In contrast, Tavurvur ash leachates indicate no seawater interaction, and later sulfur dioxide emissions remained high despite low-level eruptive activity. Silicic melt inclusions indicate that the andesitic melt contained about 2 weight percent water and negligible carbon dioxide. Mafic melt inclusions in Tavurvur ash have water and carbon dioxide contents that vary systematically over the course of the eruption. The mafic melt inclusions suggest that a mafic dike intruded from below the silicic chamber and provide further evidence that mafic intrusions drive caldera unrest.