Supercritical carbon dioxide extraction and characterization of Laurus nobilis essential oil

Supercritical carbon dioxide extraction allowed essential oil of Laurus nobilis to be obtained. Extraction conditions were as follows: pressure, 90 bar; temperature, 50 degrees C; and carbon dioxide flow, Phi = 1.0 kg/h. Waxes were entrapped in the first separator set at 90 bar and -10 degrees C. The oil was recovered in the second separator working at 15 bar and 10 degrees C. The main components were 1,8-cineole (22.8%), linalool (12.5%), alpha-terpinyl acetate (11.4%), and methyleugenol (8.1%). Comparison with the hydrodistilled oil did not reveal any significant difference. Collection of samples at different extraction times during supercritical extraction allowed the change of the oil composition to be monitored. Lighter compounds such as hydrocarbon and oxygenated monoterpenes were extracted in shorter times than the heavier hydrocarbon and oxygenated sesquiterpenes.     

Effects of biochar compared to organic and inorganic fertilizers on soil quality and plant growth in a greenhouse experiment

Our contemporary society is struggling with soil degradation due to overuse and climate change. Pre‐Columbian people left behind sustainably fertile soils rich in organic matter and nutrients well known as terra preta (de Indio) by adding charred residues (biochar) together with organic and inorganic wastes such as excrements and household garbage being a model for sustainable agriculture today. This is the reason why new studies on biochar effects on ecosystem services rapidly emerge. Beneficial effects of biochar amendment on plant growth, soil nutrient content, and C storage were repeatedly observed although a number of negative effects were reported, too. In addition, there is no consensus on benefits of biochar when combined with fertilizers. Therefore, the objective of this study was to test whether biochar effects on soil quality and plant growth could be improved by addition of mineral and organic fertilizers. For this purpose, two growth periods of oat (Avena sativa L.) were studied under tropical conditions (26°C and 2600 mm annual rainfall) on an infertile sandy soil in the greenhouse in fivefold replication. Treatments comprised control (only water), mineral fertilizer (111.5 kg N ha^–1, 111.5 kg P ha^–1, and 82.9 kg K ha^–1), compost (5% by weight), biochar (5% by weight), and combinations of biochar (5% by weight) plus mineral fertilizer (111.5 kg N ha^–1, 111.5 kg P ha^–1, and 82.9 kg K ha^–1), and biochar (2.5% by weight) plus compost (2.5% by weight). Pure compost application showed highest yield during the two growth periods, followed by the biochar + compost mixture. biochar addition to mineral fertilizer significantly increased plant growth compared to mineral fertilizer alone. During the second growth period, plant yields were significantly smaller compared to the first growth period. biochar and compost additions significantly increased total organic C content during the two growth periods. Cation‐exchange capacity (CEC) could not be increased upon biochar addition while base saturation (BS) was significantly increased due to ash addition with biochar. On the other hand, compost addition significantly increased CEC. Biochar addition significantly increased soil pH but pH value was generally lower during the second growth period probably due to leaching of base cations. Biochar addition did not reduce ammonium, nitrate, and phosphate leaching during the experiment but it reduced nitrification. The overall plant growth and soil fertility decreased in the order compost > biochar + compost > mineral fertilizer + biochar > mineral fertilizer > control. Further experiments should optimize biochar–organic fertilizer systems.     

Sensitivity of Soil P Availability Tests to Ca-P in Oxisols

We assessed the sensitivity of mixed exchange resin (MER) and Mehlich-3 (M3) to calcium-bound phosphate (Ca-P) in Oxisols. These methods were compared with Mehlich-1 (M1) and anion exchange resin (AER), which have high and low sensitivity, respectively, to this soil P form. We used maize (Zea mays L.) as a test plant. Three samples from two Oxisols were treated with five ratios of Triple Superphosphate—TS and Bayóvar Phosphate Rock—BPR (0 + 100; 25 + 75, 50 + 50, 75 + 25 and 100 + 0% TS + BPR). The MER extracted more P than AER and M3 at the highest BPR:TS ratios (high Ca-P) and similar quantities at the higher TS:BPR ratios (low Ca-P) for two soil samples. Unlike M1-extracted P, M3-P, AER-P, and MER-P positively correlated with maize dry matter production and P uptake. Mehlich-3 and MER were suitable to assess P availability in high Ca-P Oxisols.     

Effect of tillage and N fertilization on microbial physiological profile of soils cultivated with wheat

Microbial diversity might be a good indicator of ecosystem disturbance and functioning. We determined the effect of soil disturbances, such as N fertilization and tillage management, on soil microbial communities in a Typic Argiudoll of the El Salado river basin (Argentina). Microbial activity and substrate utilization provided a metabolic fingerprint of the soil microbial community. Univariate and multivariate analyses were used to differentiate responses to N fertilization and tillage at each of three growth stages of wheat (Triticum aestivum L.). Tillage had an adverse effect on microbial diversity, in which reduced and conventional tillage treated soils had different populations. However, N fertilization also altered microbial diversity depending on the crop developmental stage considered. Metabolism of carboxylic acids and carbohydrates were the main indicators of functional microbial activity and diversity. Although the substrate consumption profile of 32 C substrates did not provide insights into the fundamental ecological interactions that may induce changes in microbial population, it allowed us to demonstrate the alterations of microbial diversity as a result of tillage. We conclude that tillage and N fertilization altered microbial diversity.     

Yield and nutritional requirements of cassava in response to potassium fertilizer in the second cycle

Potassium (K) is one of the most absorbed nutrients by cassava because it acts on the synthesis and starch accumulation in the storage roots. Here, we show that K application at the beginning of the second vegetative cycle of cassava submitted to shoot pruning increased the yield of roots and starch, and the nutrient demand of plants. Application of 45–89 kg ha^?1 dipotassium oxide (K₂O) in the second cycle increased the yield of storage roots and starch from 36–49% and K applied at this time had a greater effect on the synthesis and allocation of starch in the storage roots. K supply increased the accumulation of N and S by 2.0- to 3.0-fold and the accumulation of other nutrients by 1.4- to 1.7-fold. The removal of phosphorus (P), manganese (Mn), and zinc (Zn) by storage roots was not affected by K application, whereas the removal of other nutrients increased by 1.3- to 4.3-fold.     

Losses of 15N-nitrogen by plant–soil system after herbicide application on black oat

Recent studies have demonstrated that the use of glyphosate or glufosinate-ammonium herbicides for some cover crop desiccation in conservationist systems could favor nitrogen (N) losses from the soil–plant system. In this context, the objective of this study was to evaluate the losses of N by the plant–soil system after the desiccation of black oat (Avena strigosa Schreb.) with the application of herbicides glyphosate, glufosinate-ammonium, or paraquat. Two greenhouse experiments were implemented using black oat plants fertilized with labeled (¹⁵N) ammonium nitrogen, and the N loss of the plant–soil system was quantified. The desiccation of black oat with glyphosate caused a reduction in root dry mass by approximately 60% in both experiments. The glyphosate and glufosinate-ammonium reduced the amount of N present in the aboveground portion; however, the paraquat herbicide did not modify it. None of the herbicides applied affected N losses in the black oat plant–soil system. However, 5–15% of the N applied as fertilizer was lost up to harvest. The results suggest that black oat can be used as a cover crop in direct sowing in order to avoid nitrogen losses in the soil–plant system.     

Determining milk isolated and conjugated trans-unsaturated fatty acids using fourier transform Raman spectroscopy

The feasibility of Raman spectroscopy in combination with partial least-squares (PLS) regression for the determination of individual or grouped trans-monounsaturated fatty acids (trans-MUFA) and conjugated linoleic acids (CLA) in milk fat is demonstrated using spectra obtained at two temperature conditions: room temperature and after freezing at -80 °C. The PLS results displayed capability for direct semiroutine quantification of several individual CLA (cis-9,trans-11 and trans-10,cis-12 C18:2) and trans-MUFA (trans-4-15 C18:1) in minor concentrations (below 1.0 g/100 g of milk fat). Calibration models were based on reference data cross-correlation or determined by specific scattering signals in the Raman spectra. Distinct bands for trans-MUFA (1674 cm(-1)) and CLA (1653 cm(-1)) from the trans isolated and cis,trans conjugated C ═ C bonds were identified, as well as original evidence for the temperature effect (new bands, peak shifts, and higher intensities) on the Raman spectra of fatty acid methyl ester and triacylglyceride standards, are supplied.     

A prospective study of canine infective endocarditis in northern California (1999-2001): emergence of Bartonella as a prevalent etiologic agent

A prospective study was performed (June 1999 to May 2001) to determine the incidence of infective endocarditis (IE) due to Bartonella in dogs in northern California and to compare these patients with other dogs with IE. IE was diagnosed antemortem based on clinical signs and echocardiography in 18 dogs. The etiologic agent was Bartonella sp. in 5 dogs (28%) and was diagnosed by high seroreactivity to Bartonella (titer > 1:512; range, 1:1,024-1:4,096); and confirmed postmortem by positive polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) from the infected valve and partial DNA sequencing of the citrate synthase gene (glt A). Conventional bacteria were causative agents in 7 dogs (39%). An etiologic agent was not identified in 6 dogs (33%). Bartonella vinsonii berkhoffii (n = 3), B clarridgeiae (n = 1), and a B clarridgeiae-like organism (n = 1) were identified. Blood culture was positive only for the IE case due to B clarridgeiae. All dogs with IE due to Bartonella were also seroreactive to Anaplasma phagocytophilum. All dogs with IE due to Bartonella had lesions only on the aortic valve. Of the cases of IE not due to Bartonella, 31% involved the aortic valve, 61% the mitral valve, and 8% both valves. Dogs with mitral valve IE lived longer than all dogs with aortic valve IE (P = .004) and dogs with IE of the aortic valve due to Bartonella (P = .002). In conclusion, Bartonella is a common cause of IE in dogs of northern California. A high Bartonella serologic titer (> 1:512) is useful antemortem to diagnose aortic valve IE due to Bartonella.