Reducing nitrous oxide emissions from a maize‐wheat sequence by decreasing soil nitrate concentration: effects of split application of pig slurry and dicyandiamide

Pig slurry (PS) is a valuable nitrogen (N) source for agricultural crops but the simultaneous supply of readily decomposable carbon and mineral N can result in large soil nitrous oxide (N₂O) emissions. Our objective was to determine the individual and combined effects of split PS application and addition of a nitrification inhibitor (dicyandiamide, DCD) on N₂O emissions and soil mineral N concentration in southern Brazil. Soil N₂O fluxes were measured from November 2010 to November 2011 from a maize (Zea mays L.)‐wheat (Triticum aestivum L.) sequence under various fertilizer treatments: no‐N control, PS applied in a single pre‐plant dose with or without DCD, PS split‐applied with or without DCD, and urea split‐applied. Cumulative N₂O emissions increased linearly (R² = 0.73) with increasing soil nitrate (NO₃^?) exposure, indicating that management practices aimed at reducing soil NO₃^? concentrations can decrease soil N₂O emissions. In total for the two crops, splitting PS reduced N₂O emission factors (EF) by 33%, whereas the addition of DCD reduced EF by 60 and 41% when PS was applied in single and split doses, respectively. However, splitting PS or adding DCD failed to reduce N₂O losses more than a single pre‐plant PS application in maize where background soil NO₃^? concentrations were large. The addition of DCD to PS applied as a single pre‐plant dose resulted in the largest reduction in soil N₂O emissions, whereas splitting PS with and without DCD resulted in significantly smaller abatements. Consequently, we concluded that adding DCD to PS in a single pre‐plant application is a better option than splitting PS applications for reducing soil N₂O emissions in no‐till cereal cropping systems in southern Brazil.     

Fluxes and storage of fine-grained sediment and associated contaminants in the Na Borges River (Mallorca,Spain)

Samples of suspended and fine channel bed sediment were used to examine the spatial and temporal variability in the amount of fine-grained sediment and associated contaminants temporarily stored in the Na Borges River (319 km²) in Mallorca and the relationship of such channel storage to the fluxes of fine sediment and associated contaminant through the system. This Mediterranean groundwater-dominated river drains a predominantly agricultural catchment, although urbanisation during the twentieth century has changed the catchment hydrology. A re-suspension technique was used to obtain estimates of channel storage at monthly intervals during the 2004–2005 hydrological year at eight locations along the main stem of the stream (i.e. 26 km). The estimates of fine sediment storage ranged between 0 and 13,000 g m^− 2, with a mean value of 2400 g m^− 2. Only Cu exceeded the critical threshold (36 μg g^− 1), established by existing guidelines for the contaminant content of fluvial sediment. The results demonstrated significant spatial and temporal variability, in response to the influence of urban point sources, agricultural practises, seasonal groundwater interactions and the first-flush effect. The amount of fine sediment entering storage during the study period was 515.2 t, representing the net increase in storage over the study period. As a result, the mean specific storage was 21 t km^− 1. Suspended-sediment load and temporary fine sediment storage are the two basic components of the channel sediment budget that interact to determine sediment transport through a channel system, and they can therefore be used to compute the total input of sediment and associated contaminants to the system. Accordingly, storage values were compared with estimates of suspended sediment load and associated contaminant load values at three measuring stations along the river. During the study period, storage in the main channel system represented 87% of the sediment input and 68% of the contaminant input, indicating that deposition was more important than transport. The low gradient of the main channel and the low return period (i.e. 0–2.5 years) of the flood events that occurred during the study period meant that remobilised bed sediment and associated contaminants were redeposited downstream rather than being flushed to the catchment outlet as suspended sediment. Furthermore, the river bed is dry during the summer months, allowing sealing and crusting processes to stabilise the sediment deposited during the wet season and thereby reduce its availability for remobilisation at the beginning of the next wet season. Together, these factors promote sediment deposition and storage, with the result that sediment progressively accumulate over several hydrological years until a major flood event (i.e. return period ≈ 5 years) evacuates the stored sediment.     

Nose-to-nose transmission of Salmonella Typhimurium between weaned pigs

Little attention has been paid to the possibility of transmission of Salmonella in intensive pig production systems through alternate methods, such as airborne or direct nose-to-nose contact. This experimental study tested the hypothesis of nose-to-nose transmission of Salmonella enterica serovars Typhimurium (Trial I) and Agona (Trial II) in weaned pigs using stainless steel/glass isolation cabinets. In each trial, cabinet 1 (control pigs) and cabinet 2 (sentinel pigs) were connected directly to the fan unit. Cabinet 3 (seeded pigs) was not directly linked to the fan, but was arranged to receive a constant unidirectional airflow from cabinet 2 (sentinel pigs) through a 10cm diameter hole, which also allowed nose-to-nose contact between pigs housed in these two cabinets. Air was taken out of the system through ducts connecting cabinets 1 and 3 to the exhauster. Therefore, direct contact among seeded and sentinel pigs was allowed but possible aerial transference of contaminated particles between those cabinets was prevented. The system was opened 21 days post-inoculation and tissue samples were collected for bacteriological analysis. The recovery of nalidixic acid-resistant Salmonella Typhimurium from sentinel pigs corroborates the hypothesis of nose-to-nose transmission of that pathogen in pigs. However, serovar-related differences might exist regarding the nose-to-nose transmissibility of Salmonella in pigs, since Salmonella Agona was not detected in sentinel pigs (Trial II).     

Determination of methomyl in rape seeds,oils and meals

Methomyl added to rape seeds, oils or meals was detected by a thin-layer chromatographic-enzyme inhibition technique. The limit of detection in the presence of oil or meal extractive was 20 mg or 0.01 mg/kg. The amounts of methomyl recovered from oils and meals fortified at 0.01 to 20 mg/kg were comparable to the standard. When stored at 4 °C, methomyl in oil or meals, or in chloroform extracts, was stable for at least 10 and 21 days, respectively. No degradation was observed when methomyl was heated in ethanol at 72 °C for 2 h. Methomyl and its oxime were also detected with either iodo- or chloroplatinate reagent after t.l.c. The detection limits were approximately 600 mg for methomyl and 190 for the oxime.     

Impact on C and N dynamics of simultaneous application of pig slurry and wheat straw, as affected by their initial locations in soil

The joint management of animal manures and plant biomass as straw on agricultural soils may be a viable option for reducing the environmental impacts associated with livestock production and recycling nutrients efficiently. To investigate this option, an incubation in controlled conditions examined how the simultaneous addition of ¹⁵N-labeled pig slurry and ¹³C-labeled wheat straw, either on the soil surface or incorporated into the soil, affected the mineralization of C from the organic materials and the soil N dynamics. Samples from a typic hapludalf were incubated for 95 days at 25°C with eight treatments: unamended soil (S), wheat straw left on the soil surface (Ws), wheat straw incorporated in the soil (Wi), pig slurry on the soil surface (Ps), pig slurry incorporated in the soil (Pi) and three combinations of the two amendments: Pi?+?Ws, Pi?+?Wi, and Ws?+?Ps. Carbon dioxide and ¹³CO₂ emissions and soil N content were measured throughout the incubation. Pig slurry stimulated the decomposition of straw C only when wheat straw and pig slurry were left together on the soil surface. Incorporation of both wheat straw and pig slurry did not modify straw C mineralization when compared to straw incorporation alone but this promoted a higher rate of N immobilization. The results suggest that when pig slurry is used in field under no-till conditions, the best strategy to preserve environmental quality with regard to CO₂ emissions would be to apply pig slurry underneath the crop residues.     

Effect of tillage and liming on organic matter composition in a Rhodic Ferralsol from Southern Brazil

The effects of tillage and liming on degradation of organic matter of a Rhodic Ferralsol were investigated. Samples were taken from a tillage experiment and from a trial with different levels of lime application. Organic matter was separated into the fractions of undecomposed organic matter and humic substances by density fractionation. Chemical composition of the humic substances was determined by Kononova's fractionation method. Other chemical parameters measured were total organic C, pH, exchangeable cations, and the physical property determined was aggregate stability. Tillage, and to a lesser degree, liming, substantially decreased organic matter content when compared to samples taken from a virgin forest. The proportion of humic acids C (HC) varied most, so that the ratio of fulvic acids C (FC) to HC increased from 2.5 (virgin forest), to 3.4 (lime treatments and no-tillage) and to 5.8 (conventional tillage). Content of FC was affected by pH, while no distinct factors were found to influence HC content. Aggregate stability was best related to content of HC, confirming the importance of this fraction of organic matter for aggregation. It was concluded that especially excessive tillage greatly affects soil fertility because organic matter is decomposed to a great extent. However, a further need for research seems necessary to clarify interactions conclusively between changes of pH, adsorption of humic substances and other chemical properties in the entire profile of Ferralsols.     

Multi-year,post-harvesting impact assessment in a neotropical secondary Atlantic Forest

European Journal of Forest Research - Subject to overexploitation in the past centuries, the Atlantic Forest is subject to very rigorous protection rules. However, the law is a controversial issue...     

Utilization of Passion Fruit Skin By-Product as Lead(II) Ion Biosorbent

The impact of three commercially available nanoparticles (NPs) on trichloroethylene (TCE) adsorption onto granular activated carbon (GAC) was investigated. TCE adsorption isotherm and column breakthrough experiments were conducted in the presence and absence of silicon dioxide, titanium dioxide, and iron oxide nanoparticles. A rapid small-scale column test (RSSCT) was assessed for its ability to predict TCE adsorption in pilot-scale GAC in the presence and absence of NPs. Zeta potential of the three NPs and the GAC were measured. Particle size distribution of the NP dispersions was analyzed as a function of time. The surface area and the pore size distribution of the virgin and the exhausted GAC were obtained along with transmission electron microscopy and Fourier transform infrared spectroscopy analysis. The effect of NPs was found to be a function of their zeta potential, concentration, and particle size distribution. Due to their electrical charge, NPs attached to the GAC and blocked the pores and thus reduced the access to the internal pore structure. However, due to the fast adsorption kinetics of TCE, no effect from the three NPs was observed in the isotherm and kinetic studies. The RSSCT, on the other hand, accurately predicted the pilot-column TCE breakthrough in the presence of NPs.