Rates of Chlorimuron Applied in Glyphosate-Tolerant and Sulfonylurea-Tolerant Soybean

Susceptibility to chlorimuron varies according to soybean genotype. STS® (sulfonylurea-tolerant soybean) presents a high tolerance to some sulfonylureas; this feature is determined by semi-dominants alleles, Als1 and Als2. Experiments were conducted in the field for four seasons with two cultivars for season to evaluate the selectivity of chlorimuron rates in post-emergency (V4) of glyphosate-tolerant and sulfonylurea-tolerant soybean. Data analysis made it possible to infer that there was no significant effect on the productivity of the cultivars when they received application in post-emergency, of chlorimuron at the doses used (0, 15, 30, 45, 60, 75, and 90 g ai ha^-1). The maximum recommended rate for non-STS cultivars of chlorimuron is 20 g ai ha^-1, or 4.5 times less than the maximum rate employed in this study. The soybean cultivars CD 250 RR/STS, CD 236 RR/STS, CD 2630 RR/STS, and BMX Turbo RR/STS were tolerant to the application, in post-emergency (V4) of the herbicide chlorimuron, until the rate of 90 g ai ha^-1.     

Sorption-desorption isotherms and biodegradation of glyphosate in two tropical soils aged with eucalyptus biochar

ABSTRACT

The objective of this study was to evaluate the sorption-desorption process and biodegradation of glyphosate in two tropical soils aged with biochar derived from eucalyptus. The biochar aging period was 30 d. There was little difference between the amounts of sorbed glyphosate in Ultisol (96.8, 96.8 and 96.4%) and Alfisol (97.1, 97.5 and 97.4%) soils that were unamended or amended with biochar aged for 0 or 30 d, respectively. Similar amounts of desorbed herbicide occurred in Ultisol (3.3, 3.3 and 3.4%) and Alfisol (4.1, 4.2 and 3.9%) soils, respectively. The degradation time half-life (DT50) of glyphosate in Ultisol unamended and initial amended were higher (38 and 36 d, respectively) than DT50 in the amended soil with 30 d of biochar aging (27 d); and in the Alfisol DT50 was higher in unamended soil (38 d), and similar in soil unamended at 0 and 30 d of biochar aging (21 and 26 d, respectively). The addition of biochar to two tropical soils or its aging did not have any effect on the sorption and desorption of glyphosate and its biodegradation in relation to the unamended soils, and it can did not affect the transport and persistence of this herbicide in soil.     

Chemical and spectroscopic characteristics of humic acids in marshes from the Iberian Peninsula

Purpose

To characterise soil humic acids (HAs) extracted from Spanish marshes formed under different vegetation types (Spartina maritima (GSp), Juncus maritimus (GJc), Phragmites australis (GPh), and Scirpus maritimus (VSc)), soil depths (0–20, 20–40 and 40–60 cm), physiographic position (low and high marshes), wetland types (salt marshes and lagoons) and environmental conditions (Atlantic and Mediterranean coast).

Material and methods

Soil samples were collected in five Spanish marshes, three on the Galicia province and two on the Valencia province. Humic acids were extracted and their elemental composition, semiquinone-type free radical (SFR) content, FTIR and CPMAS ¹³C NMR spectra determined. Total carbon (TC), total nitrogen (TN), total sulphur (TS), CaCO₃ content, and field pH and Eh (mV) in the marsh soils sampled were also measured.

Results and discussion

The field pH and Eh values were typical of coastal areas submitted to periodic inundations and the highest TC, TN and TS contents were found in the soil of lagoon marshes as an effect of physiographic position and wetland type. The HAs, in general, were highly aliphatic and exhibited a low SFR content, which suggests a low humification degree of the SOM formed in the studied areas. This is a result of the anaerobic decomposition to which SOM is submitted and the high input of plant-derived organic matter (OM) by vegetation. However, among the studied sites low salt marsh and subsurface layer of the high salt marsh showed higher SFR content, simpler FTIR spectra, higher lignin degradation and lower O-alkyl C/alkyl C ratio than the lagoon marshes, thus suggesting the presence of a more humificated SOM in these sites.

Conclusions

From the different factors analysed, only physiographic position (low versus high salt marshes) and wetland type (marshes versus lagoons) caused variations in the HAs characteristics, because as the studied soils are under anaerobic conditions, they control the exportation of plant-derived OM and the allochthonous OM contribution in the studied areas.     

Spatial patterns of soil attributes and components in a mangrove system in Southeast Brazil (São Paulo)

Purpose

Among environmental factors governing innumerous processes that are active in estuarine environments, those of edaphic character have received special attention in recent studies. With the objectives of determining the spatial patterns of soil attributes and components across different mangrove forest landscapes and obtaining additional information on the cause–effect relationships between these variables and position within the estuary, we analyzed several soil attributes in 31 mangrove soil profiles from the state of São Paulo (Guarujá, Brazil).

Materials and methods

Soil samples were collected at low tide along two transects within the Crumahú mangrove forest. Samples were analyzed to determine pH, Eh, salinity, and the percentages of sand, silt, clay, total organic carbon (TOC), and total S. Mineralogy of the clay fraction (<2 mm) was also studied by X-ray diffraction analysis, and partitioning of solid-phase Fe was performed by sequential extraction.

Results and discussion

The results obtained indicate important differences in soil composition at different depths and landscape positions, causing variations in physicochemical parameters, clay mineralogy, TOC contents, and iron geochemistry. The results also indicate that physicochemical conditions may vary in terms of different local microtopographies. Soil salinity was determined by relative position in relation to flood tide and transition areas with highlands. The proportions of TOC and total S are conditioned by the sedimentation of organic matter derived from vegetation and by the prevailing redox conditions, which clearly favored intense sulfate reduction in the soils (～80% of the total Fe is Fe-pyrite). Particle-size distribution is conditioned by erosive/deposition processes (present and past) and probably by the positioning of ancient and reworked sandy ridges. The existing physicochemical conditions appear to contribute to the synthesis (smectite) and transformation (kaolinite) of clay minerals.

Conclusions

The results demonstrate that the position of soils in the estuary greatly affects soil attributes. Differences occur even at small scales (meters), indicating that both edaphic (soil classification, soil mineralogy, and soil genesis) and environmental (contamination and carbon stock) studies should take such variability into account.

     

Absence of Transgenerational Phenotypic Plasticity in Fecundity in the Parasitoid Anagrus erythroneurae (Hymenoptera: Mymaridae)

To improve biological pest control, we would like to understand the main factors that limit the reproductive success of key biological control agents, including parasitoid wasps. Previous research with proovigenic parasitoids in the genus Anagrus collected from multiple field sites revealed positive correlations between parasitoid fecundity and local host density. In this article, we test whether this variation in fecundity is a reflection of transgenerational phenotypic plasticity. We exposed females in laboratory microcosms to either low or high host densities and then quantified the fecundity of their adult daughters. Mean fecundity of daughters did not differ across host density treatments, arguing against the operation of phenotypic plasticity. Significant variation in mean fecundity across different families instead suggested the possibility that genetic variation may underlie the observed fecundity differences.     

Unmanned aerial vehicle to evaluate frost damage in coffee plants

Damage caused by frost on coffee plants can impact significantly in the reduction of crop quality and productivity. Remote sensing can be used to evaluate the damage caused by frost, providing precise and timely agricultural information to producers, assisting in decision making, and consequently minimizing production losses. In this context, this study aimed to evaluate the potential use of multispectral images obtained by unmanned aerial vehicle (UAV) to analyze and identify damage caused by frost in coffee plants in different climatic favorability zones. Visual evaluations of frost damage and chlorophyll content quantification were carried out in a commercial coffee plantation in Southern Minas Gerais, Brazil. The images were obtained from a multispectral camera coupled to a UAV with rotating wings. The results obtained demonstrated that the vegetation indices had a strong relationship and high accuracy with the frost damage. Among the indices studied the normalized difference vegetation index (NDVI) was the one that had better performances (r?=?? 0.89, R²?=?0.79, MAE?=?10.87 e RMSE?=?14.35). In a simple way, this study demonstrated that multispectral images, obtained from UAV, can provide a fast, continuous, and accessible method to identify and evaluate frost damage in coffee plants. This information is essential for the coffee producer for decision-making and adequate crop management.

     

Weak connectivity and population cohesiveness in rudderfish Kyphosus sandwicensis (Teleostei: Kyphosidae) inhabiting remote oceanic islands

1. Population connectivity has a fundamental role in metapopulation dynamics, with important implications in conservation. Easter Island (EI) and Salas y Gómez Island (SG) in the Pacific Ocean are ideal for the study of population connectivity because they are separated by 415 km and isolated from other islands in the Pacific Ocean by >2,000 km.
2. Considering that dispersal processes could play a critical role in the persistence of its populations, the connectivity pattern of the rudderfish Kyphosus sandwicensis was evaluated between EI and SG using both a population genetics and a biophysical modelling approach.
3. The variability in the control region of the mitochondrial DNA did not show a significant phylogeographical pattern, and the variability in 16 microsatellite loci suggested that individuals of K. sandwicensis located at EI and SG belong to the same genetic population. However, historical migration showed that 0.2% of the recruits at EI come from SG and that 0.15% at SG come from EI per year.
4. Using simulated larval release during September and a larval development of 30 days in the plankton, biophysical modelling did not detect migration between the islands. Furthermore, self-recruitment shows interannual variation ranging from 5 to 10% of the total released larvae.
5. Whereas the genetic data showed a lack of population genetic structure but low connectivity of K. sandwicensis between EI and SG, the biophysical modelling showed null movement of particles between the islands. Stochastic movement of larvae or adults could explain the pattern observed, with rafting as an example. These low-frequency and stochastic movements may be important in maintaining the cohesiveness between EI and SG.

     

Polyculture of Freshwater Angelfish Pterophyllum scalare and Pacific white shrimp Litopenaeus vannamei in low‐salinity water

In this study, we evaluated the production potential of the polyculture of Freshwater Angelfish (Pterophyllum scalare, Cichlidae) and Pacific white shrimp (Litopenaeus vannamei). Two experimental trials were set up. The first trial entailed the use of a randomized design to investigate three treatments options: angelfish monoculture, shrimp monoculture, and fish and shrimp polyculture in 12 experimental 15 m² ponds. In the second trial, we investigated two treatments (polyculture of caged fish and uncaged fish) in 10 experimental units. In trial 1, polyculture negatively affected fish growth and survival. However, fish did not affect shrimp growth and the greatest profit was achieved in polyculture. In trial 2, caging fish improve the growth of both fish and shrimp. An economic analysis showed the greatest profit and benefit cost ratio for caged fish compared with uncaged fish. We conclude that growing P. scalare and L. vannamei together is a better strategy than shrimp monoculture in low‐salinity water. The use of caged fish in such a polyculture operation would enhance productivity and profitability.     

An insight on Octopus vulgaris paralarvae lipid requirements under rearing conditions

In this study, two new alternative preys: Grapsus adscensionis zoeae (as sole prey) and Palaemon elegans zoeae (in cofeeding with Artemia sp.), as well as, Artemia sp. juveniles were used as feed for octopus paralarvae, as a way to understand its lipid requirements. Total lipid (TL) content, lipid class (LC) and fatty acid (FA) profiles of preys, octopus hatchlings and 9‐day‐old paralarvae were analysed. Growth and survival of the paralarvae were also determined. Regardless the prey provided, a notable shift in the lipid profile of paralarvae was registered after 9 days of rearing. The highest index of growth rate (IGR) recorded when decapod crustacean zoeae were supplied might have some relation with levels of 20:4n‐6 (ARA) and DHA/EPA ratio observed. In this sense, Grapsus adscensionis zoeae leaded to a higher content of ARA and a lower content of EPA, which may indicate a possible competition between these two FA. For that a balanced EPA/ARA ratio might be significant in this species nutrition without disconsidering DHA levels as an essential fatty acid. Finally, the changes observed in paralarvae FA profile might not only be related to prey FA profile, but also with changes occurring in the lipid classes contents.     

Effects of soy protein ratio,lipid content and minimum level of krill meal in plant‐based diets over the growth and digestibility of the white shrimp,Litopenaeus vannamei

This study evaluated the effects of soy protein ratio, lipid content and the minimum dietary level of krill meal in plant‐based diets over the growth performance and digestibility of Litopenaeus vannamei. Nine plant‐based diets varied the soybean meal (SBM) and soy protein concentrate (SPC) inclusion ratio at 1 : 2.3, 1 : 1 and 2.5 : 1, and their dietary lipid content at 121.4 ± 9.4, 102.3 ± 1.2, and 79.9 ± 1.2 g kg^?1 (in a dry matter basis). An additional diet containing 120 g kg^?1 of fish meal (salmon by‐product) was used as a control. Krill meal was included at 0, 5, 10, 20 and 30 g kg^?1 in a new set of plant‐based diets. After 10 weeks in clear‐water tanks of 0.5 m³, no effect of SBM:SPC ratio and dietary lipid content was detected on shrimp survival. However, dietary lipid levels of 80 and 121 g kg^?1 combined with a high SPC to SBM resulted in the lowest final body weight and the poorest apparent crude protein digestibility, respectively. Krill meal increased feed intake at only 10 g kg^?1, while at 20 g kg^?1, it accelerated shrimp growth, increased yield and reduced food conversion ratio.