For how long does the quality and quantity of residues in the soil affect the carbon compartments and CO<Subscript>2</Subscript>-C emissions?

Purpose

The mineralization/immobilization of nutrients from the crop residues is correlated with the quality of the plant material and carbon compartments in the recalcitrant and labile soil fractions. The objective of this study was to correlate the quality and quantity of crop residues incubated in the soil with carbon compartments and CO₂-C emission, using multivariate analysis.

Materials and methods

The experiment was conducted in factorial 4?+?2?+?5 with three replicates, referring to three types of residues (control, sugarcane, Brachiaria, and soybean), and two contributions of the crop residues in constant rate, CR (10 Mg ha^?1 residue), and agronomic rate, AR (20, 8, and 5 Mg ha^?1 residue, respectively, for sugarcane, soybean, and Brachiaria), evaluated five times (1, 3, 6, 12, and 48 days after incubation). At each time, we determined the CO₂-C emission, nitrogen and organic carbon in the soil, and the residues. In addition, the microbial biomass and water-soluble, labile, and humic substance carbons fractionated into fulvic acids, humic acids and humin were quantified.

Results and discussion

Higher CO₂-C emissions occurred in the soil with added residue ranging from 0.5 to 1.1 g CO₂-C m^?2 h^?1 in the first 6 days of incubation, and there was a positive correlation with the less labile organic soil fractions as well as residue type. In the final period, after 12 days of soil incubation, there was a higher relation of CO₂-C emission with carbon humin. The sugarcane and soybean residue (20 Mg ha^?1) promoted higher CO₂-C emission and the reduction of carbon residue. The addition of residue contributed to an 82.32 % increase in the emission of CO₂-C, being more significant in the residue with higher nitrogen availability.

Conclusions

This study shows that the quality and quantity of residue added to soil affects the carbon sequestration and CO₂-C emission. In the first 6 days of incubation, there was a higher CO₂-C emission ratio which correlates with the less stable soil carbon compartments as well as residue. In the final period of incubation, there is no effect of quality and quantity of residue added to soil on the CO₂-C emission.

     

Organic carbon pools in a Luvisol under agroforestry and conventional farming systems in the semi-arid region of Ceará, Brazil

Many environmental benefits have been attributed to agroforestry systems in various ecosystems around the world. However, there is a limited amount of information to evaluate this agricultural system in the semi-arid region, specifically in the region of Ceará, Brazil. The objective of this work was to evaluate five agricultural (four agroforestry and one conventional) systems in order to test the hypothesis that the agroforestry systems promote an increase in the soil organic carbon stocks and organic carbon pools, thus improving soil quality. The following treatments were tested: agrosilvopasture (AGP), silvopasture (SILV), traditional agroforestry (TRAG), intensive cropping (IC), and native forest (NF). The soil samples were collected at four depths: 0–6, 6–12, 12–20 and 20–40 cm. Total soil organic carbon stocks and the organic carbon pools (microbial biomass-C, mineralizable-C, oxidizable-C, free, occluded light fraction organic matter, and C in the humic substances) were analyzed. After 5 years of experimental cultivation, the soil under the SILV system presented the best results for the attributes studied, preserving, and in some cases, improving these attributes, when compared to the other conditions. The traditional agroforestry system (TRAG) reduced total organic carbon stocks and, consequently, C in some organic matter compartments, indicating that the fallow period was not sufficient to maintain soil quality. The AGP and IC systems presented significant losses in some of the soil organic matter (SOM) pools, suggesting that the soil environment had been degraded. The most labile SOM components were considered sensitive indicators of change in the soil quality. The silvopasture system can, therefore, be recommended as an alternative soil management strategy for food production and for the maintenance of soil quality and agricultural sustainability in the semiarid region of Ceará state.     

Bioeconomic effect from the size selection in red abalone intensive culture Haliotis rufescens as a production strategy

The variability in growth is a common characteristic in mollusks breeding. Effects rising from the variability in the individual growth rate and the consequent dispersion of sizes in cultivation are important in financial terms. To manage this heterogeneity many firms use size selection, which can happen in two stages: toward the end of the stage of growing, or in the phase of growing of seeds. A bioeconomic model simulating the operation of a firm producing red abalone was implemented in spreadsheets. The firm produces 70 tons yearly. The model was structured in three sub-models. A biological sub-model detailed a batch’s dynamics, in terms of survival and growth, considering individual variation of size around a central value for each age. A technological sub-model described raw materials, the quantity of food and the energy required. Finally, the simulation model is completed with an economic integrated sub-model, where net present value is calculated considering income and costs over the time. Results of the alternative production strategies (with or without selection) are assessed according to: quantity of larvae and necessary spawners to reach the desired level of production; net present value (NPV) and necessary time to recover the investment. The number of larvae was approximately 17 millions larger for the case of the strategy of production with sizes selection and 73% more of available spawners is required for this larger amount of larvae. In the short term, the size-selection strategy increases the production costs at the initial time, compared with the strategy without selection. However, in the long term, this strategy generates greater NPV. The span for investment recovery was shorter for the case of the strategy with size selection and living product (nearly 2,140 days) than frozen (nearly 2,232 days); while without sizes selection a 15-year simulation showed the investment is not recovered. Finally, could be verified that size selection can be an interesting strategy to explore, since it improves the financial result, the same way other more expensive technological changes would.     

Identification of ISSR markers linked to flowering traits in a representative sample of <Emphasis Type="Italic">Eucalyptus cladocalyx</Emphasis>

Early flowering and flower abundance have long been considered desirable traits in eucalypt breeding programs. In particular, flowers of Eucalyptus cladocalyx provide a nectar source for the production of honey in arid ecosystems. To identify inter-simple sequence repeat (ISSR) markers that are associated with early flowering and flower abundance in the southern Atacama Desert, we used a sample of 47 trees, representing five Australian provenances of E. cladocalyx. A unified mixed linear model (which considered the effect of genetic structure and the kinship relationship among trees) revealed that three loci were significantly associated with early flowering, which accounted for 10–16 % of the phenotypic variation, while two loci accounted for 11–13 % in flowering intensity. Locus ISO_{1–500 bp} was associated with both flowering traits. This result is consistent with our previous findings indicating that marker-assisted selection on early flowering should have significant and positive impact on flowering intensity. The application of marker-assisted selection to identify trees that flower early and intensively may increase honey production, a resource that generates additional income for the local farmers of the southern Atacama Desert.     

Effects of iron-ore mining and processing on metal bioavailability in a tropical coastal lagoon

Background, aim, and scope

In water systems, water quality and geochemical properties of sediments determine the speciation of trace metals, metal transport, and sediment–water exchange, influencing metal availability and its potential effects on biota. Studies from temperate climates have shown that iron-ore mining and tailing wastewaters, besides being a source of trace metals, usually show high levels of dissolved ions and particulate suspended matter, thus having the potential of indirectly changing metal bioavailability. For the first time in the tropics, we identified the effects of iron-ore mining and processing on metal bioavailability in a coastal lagoon. With an extensive sampling scheme, we investigated the potential sources of metals; the links among metal levels in water, sediments, and invertebrates; and the contrasting effects on metal speciation and bioavailability.

Methodology

The metals Fe, Mn, Al, Cr, Zn, Cu, Ni, Pb, Cd, Hg, and As were measured in water, sediments (surface and profiles), and invertebrates from Mãe-Bá Lagoon and in the sites directly influenced by the mining operations (tailing dams and nearby rivers). In addition, samples from two other lagoons, considered pristine, were analyzed. The study area is located in the southeast of Brazil (Iron Quadrangle Region and a coastal area of Espírito Santo State). General water characteristics included pH, dissolved organic carbon, alkalinity, and anion composition. Water metal speciation was assessed by a speciation model (Chemical Equilibria in Aquatic Systems). Grain-size distribution, organic carbon, carbonate, and acid volatile sulfide (AVS) were determined in sediments. Statistical methods included comparison of means by Mann–Whitney test, ordination and correlation analyses, and analysis of regression for geochemical normalization of metals with grain size.

Results and discussion

The dissolved metal concentrations, the total metal levels in sediments, and the normalization based on the fine sediment fraction showed that the mining operations constitute potential sources of Fe, Mn, Cr, Cu, Ni, Pb, As, and Hg to Mãe-Bá Lagoon. However, trace metal availability was reduced because of increased pH, hardness, and sulfide content (356 μmol/g) in the sites influenced by the mining. The lagoon showed similar water chemistry as in the mining sites, with metal bioavailability further decreased by the presence of dissolved organic carbon and chloride. Although AVS levels in the lagoon were low (0.48–56 μmol/g), metal bioavailability was reduced because of the presence of organic matter. Metal levels in invertebrates confirmed the predicted low metal bioavailability in Mãe-Bá Lagoon. The lagoon was considered moderately contaminated only by Hg and As.

Conclusions

The iron-ore mining and processing studied here constitute potential sources of metal pollution into the tropical lagoon. Contrary to expectations, however, it also contributes to reducing the overall metal bioavailability in the lagoon.

Recommendations and perspectives

These findings are believed to be useful for evaluating metal exposure in a more integrated way, identifying not only the sources of pollution but also how they can affect the components involved in metal speciation and bioavailability in water systems, leading to new insights.     

Bound malondialdehyde in foods: bioavailability of N,N'-di-(4-methyl-1,4-dihydropyridine-3,5-dicarbaldehyde)lysine

Reactions between lipid peroxidation products and proteins in foods have detrimental nutritional effects, most importantly, losses of essential amino acids. One of the major products of the reaction of malondialdehyde and alkanals with amino groups are 4-substituted 1,4-dihydropyridine-3,5-dicarbaldehyde derivatives. The product of the reaction of lysine with malondialdehyde and acetaldehyde, N,N'-di-(4-methyl-1,4-dihydropyridine-3,5-dicarbaldehyde)lysine (MDDL), has been synthesized and used for in vitro and in vivo bioavailability studies. Release of free lysine did not occur in incubations of MDDL with tissue homogenates. After oral administration of radioactively labeled MDDL, radioactivity was only recovered in feces. Radioactivity was not incorporated into hepatic microsomes after intraperitoneal administration, which would have indicated release of available lysine. These results show that MDDL is a form of unavailable lysine, because it is not metabolized to free lysine and cannot be absorbed from the gut. Thus, formation of this derivative in foods would result in loss of available lysine.     

Colletotrichum siamense is the main aetiological agent of anthracnose of avocado in south-eastern Brazil

Anthracnose caused by species of Colletotrichum is considered one of the main postharvest diseases for avocado. In this study, Colletotrichum isolates associated with avocado anthracnose, collected in different states of Brazil, were evaluated through phylogenetic analysis, morphological characterization, and pathogenicity assays. Moreover, the events during pathogen infection of avocados were examined by scanning electron microscopy. To assess the genetic diversity of 54 Colletotrichum isolates, partial sequence analysis of the gene gapdh was performed. According to the generated groupings and the geographical origins of isolates, a subset of 14 strains was selected for performing multilocus phylogeny analysis (using sequences of gapdh, act, tub2, and ApMat). Two species previously described were identified: C. siamense belonging to the C. gloeosporioides species complex and Colletotrichum karstii belonging to the C. boninense species complex. All Colletotrichum strains evaluated caused typical symptoms of anthracnose in avocado fruits. Conidia of the most virulent strain germinated between 6 and 12 hr after inoculation (hai). Penetration through wounds occurred 48 hai, tissue colonization occurred between 144 and 240 hai, and sporulation took place at 240 hai via the production of an acervulus, conidiophores, and conidia. The findings shed light on the aetiology of avocado anthracnose in Brazil and provide a better understanding of the infection process of this pathogen, which may assist in the development of disease management strategies.     

Effect of lactating sows’ diet supplemented with cactus (Opuntia ficus-indica) on feed intake and reproductive and productive post-weaning performances

Tropical Animal Health and Production - The effect of cactus (Opuntia ficus-indica) added to the diet of lactating (21&nbsp;days of lactation) sows on voluntary feed intake, and its impact on...     

Contact,fumigant, and cytotoxic activities of thyme and lemongrass essential oils against larvae and an ovarian cell line of the cabbage looper,Trichoplusia ni

The chemical composition of a plant essential oil can be affected by many environmental and biological factors. Understanding the role of individual constituents as well as their interactions to the overall insecticidal bioactivity is prerequisite to the use of essential oils as an alternative to conventional insecticides. In the present study, the chemical compositions of plant essential oils obtained from Thymus vulgaris (thyme) and Cymbopogon citratus (lemongrass) were analyzed by gas chromatography/mass spectrometry, and the insecticidal and cytotoxic activities of individual constituents were evaluated against third instar larvae and an ovarian cell line of Trichoplusia ni. Thymol was the most abundant compound in thyme oil and the primary active constituent in contact and cytotoxicity tests, whereas p-cymene was the most effective compound for fumigant toxicity. In lemongrass oil, citral was identified as the major active and most abundant constituent. A weak correlation between insecticidal activity and cytotoxicity was observed, indicating limitation of the latter as a screening tool for novel insecticides. Although the evaporation of thymol was enhanced at higher temperatures, its contribution to fumigant activity was limited.