Agronomic performance of no-tillage relay intercropping with maize under smallholder conditions in Central Brazil

In the context of conservation agriculture on small scale farms of the Brazilian Cerrado, we hypothesized that planting a cover crop in relay with a commercial crop improves the efficiency of use of available natural resources, increasing biomass for use as fodder without reducing the grain yield of the main crop. The objective of this study was to measure the performance of two intercropped systems in terms of total above-ground biomass production and maize (Zea mays) grain yield: pigeon pea (Cajanus cajan) and Brachiaria (Brachiaria ruziziensis) sown as cover crops in established maize under a no-tillage management. The cover crops were sown at two different dates and a comparison was made with the three crops sown as a sole crop at the early sowing date. The experiment was conducted during the 2007-2008 and 2008-2009 growing seasons. Maize grain yield was not reduced by the presence of the relay cover crops in comparison with maize as the sole crop, even when the cover crop was sown soon after maize emergence. In contrast, the production of above-ground biomass by the cover crop was significantly lower when grown with maize than it was when grown as a sole crop. In the intercropped systems, when sown early, the cover crop produced higher total biomass than when sown late. Total above-ground biomass production of maize intercropped with a cover crop was much higher than that of any of the crops sown alone: the total biomass (average of the two growing seasons) produced by maize and pigeon pea was more than double that of maize grown alone. The land equivalent ratio (LER) of maize grain yield and biomass production was higher than one whatever the intercropped system used. It was particularly high when maize was intercropped with early sown pigeon pea; grain yield LER and biomass LER reaching, respectively, 1.72 and 1.73 in 2007-2008 and 2.02 and 2.03 in 2008-2009. These high LER values provide evidence for the complementary and the high efficiency of use of available resources by the intercropped plants and thus the advantage of such systems to produce both maize grain and cover crop forage under the conditions of our study.     

Comparison between empirical protein force fields for the simulation of the adsorption behavior of structured LK peptides on functionalized surfaces

All-atom empirical molecular mechanics protein force fields, which have been developed to represent the energetics of peptide folding behavior in aqueous solution, have not been parameterized for protein interactions with solid material surfaces. As a result, their applicability for representing the adsorption behavior of proteins with functionalized material surfaces should not be assumed. To address this issue, we conducted replica-exchange molecular dynamics simulations of the adsorption behavior of structured peptides to functionalized surfaces using three protein force fields that are widely used for the simulation of peptide adsorption behavior: CHARMM22, AMBER94, and OPLS-AA. Simulation results for peptide structure both in solution and when adsorbed to the surfaces were compared to experimental results for similar peptide-surface systems to provide a means of evaluating and comparing the performance of these three force fields for this type of application. Substantial differences in both solution and adsorbed peptide conformations were found amongst these three force fields, with the CHARMM22 force field found to most closely match experimental results.     

Distribution and composition of phytosterols and steryl ferulates in wheat grain and bran fractions

Phytosterols and steryl ferulates are bioactive compounds accumulating in the bran and germ of wheat. However, little is known regarding their localisation and composition in the bran layers of the kernel. The aim of this study was to determine the distribution of phytosterols and steryl ferulates in the wheat grain and in the different layers of bran. The wheat fractions, produced by conventional debranning, aleurone separation and a novel electrostatic process, were analysed for phytosterol contents using GC–FID and for steryl ferulate contents using HPLC–UV. The compounds were identified by GC– and LC–MS. Phytosterols and steryl ferulates were concentrated in the bran layers. The steryl ferulates were accumulated in the intermediate layers, whereas the phytosterols were more evenly distributed in the intermediate layers and aleurone cell contents. The phytosterol composition varied within the wheat kernel, while the steryl ferulate composition was similar in different fractions. Sitosterol and campestanyl ferulate were the main compounds. The highest levels of phytosterols (up to 2117 μg/g) and steryl ferulates (up to 703 μg/g) were found in the pearling, aleurone and certain bran fractions. The phytosterol-rich fractions could be utilised in cereal foods to enhance the intake of health-promoting compounds from natural sources.     

A specialist-generalist classification of the arable flora and its response to changes in agricultural practices

Background  

Theory in ecology points out the potential link between the degree of specialisation of organisms and their responses to disturbances and suggests that this could be a key element for understanding the assembly of communities. We evaluated this question for the arable weed flora as this group has scarcely been the focus of ecological studies so far and because weeds are restricted to habitats characterised by very high degrees of disturbance. As such, weeds offer a case study to ask how specialization relates to abundance and distribution of species in relation to the varying disturbance regimes occurring in arable crops.     

Effect of Solvent System on Extractability of Lipidic Components of Scenedesmus obliquus (M2-1) and Gloeothece sp. on Antioxidant Scavenging Capacity Thereof

Microalgae are well known for their biotechnological potential, namely with regard to bioactive lipidic components—especially carotenoids and polyunsaturated fatty acids (PUFA), well-known for therapeutic applications based on their antioxidant capacity. The aim of this work was to evaluate the influence of four distinct food-grade solvents upon extractability of specific lipidic components, and on the antioxidant capacity exhibited against both synthetic (2,2-diphenyl-1-picrylhydrazyl (DPPH^•) and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS^+•)) and biological reactive species (O₂^•− and ^•NO⁻). A eukaryotic microalga (Scenedesmus obliquus (M2-1)) and a prokaryotic one (Gloeothece sp.) were used as case studies. Concerning total antioxidant capacity, the hexane:isopropanol (3:2) and acetone extracts of Sc. obliquus (M2-1) were the most effective against DPPH^• and ABTS^+•, respectively. Gloeothece sp. ethanol extracts were the most interesting scavengers of O₂^•−, probably due the high content of linolenic acid. On the other hand, acetone and hexane:isopropanol (3:2) extracts were the most interesting ones in ^•NO⁻ assay. Acetone extract exhibited the best results for the ABTS assay, likely associated to its content of carotenoids, in both microalgae. Otherwise, ethanol stood out in PUFA extraction. Therefore, profiles of lipidic components extracted are critical for evaluating the antioxidant performance—which appears to hinge, in particular, on the balance between carotenoids and PUFAs.     

Ecological standards for eutrophication and desiccation: Perspectives for a risk assessment

This paper describes an assessment of ecological standards for eutrophication and desiccation using the ecotoxicological approach of standard setting. In ecotoxicological risk assessment single-species toxicity data, such as No Observed Effect Concentration (NOEC), are used to extrapolate maximum tolerable concentrations (MTC) which protect 95% of the ecosystem's species. In our approach single-species data consist of the species-response function for both nutrient availability and soil moisture. These data were used to calculate the maximum levels at which 95% of the plant species are protected. A case study, using data on 275 plant species of usable grasslands in the province of South Holland, has been carried out. Ecological standards are calculated for maximum nitrogen load and changes in groundwater level. The influence of nitrogen limitation and moisture shortage on the 95% species protection level is considered. Differences in methodology between our approach and the assessment of ecological standards for micro-pollutants and critical loads are evaluated.     

A new vision-based approach to differential spraying in precision agriculture

One of the objectives of precision agriculture is to minimize the volume of herbicides by using site-specific weed management systems. To reach this goal, two major factors need to be considered: (1) the similarity of spectral signatures, shapes, and textures between weeds and crops and (2) irregular distribution of weeds within the crop. This paper outlines an automatic computer vision method for detecting Avena sterilis, a noxious weed growing in cereal crops, and differential spraying to control the weed. The proposed method determines the quantity and distribution of weeds in the crop fields and applies a decision-making strategy for selective spraying, which forms the main focus of the paper. The method consists of two stages: image segmentation and decision-making. The image segmentation process extracts cells from the image as the low-level units. The quantity and distribution of weeds in the cell are mapped as area and structural based attributes, respectively. From these attributes, a multicriteria decision-making approach under a fuzzy context allows us to decide whether any given cell needs to be sprayed. The method was compared with other existing strategies.     

Acute Toxicity of Ammonia and Nitrite to White Shrimp Penaeus setiferus Postlarvae

Penaeus setiferus postlarvae were exposed to acute levels of ammonia, nitrite, and to a mixture of both by a short-term static method, The 24h, 48-h and 72-h LC50 values for un-ionized ammonia were 1.49, 1.21 and 1.12 mg/L NH₃-N (un-ionized ammonia as nitrogen), and 11.55, 9.38 and 8.69 mg/L ammonia-N (un-ionized plus ionized ammonia as nitrogen). The 24-h, 48-h and 72-h LC50 values for nitrite were 268.06, 248.84 and 167.33 mg/L nitrite-N (nitrite as nitrogen). Nitrite was much less toxic than ammonia. The joint effect of ammonia and nitrite on the postlarvae was synergistic at 48-h exposure and antagonistic after 72 h. Postlarvae of P. setiferus may be considered as organisms sensitive to ammonia and nitrite.