Subsoil improvement in a tropical coarse textured soil: Effect of deep-ripping and slotting

In many coarse textured soils, limited root development and biomass production are attributed to adverse physical conditions in the subsoil. The current study was undertaken on an Arenic Acrisol located in Northeast Thailand (i) to assess whether subsoil physical characteristics influence crop rooting depth, and (ii) to compare the benefits associated with conventional tillage with that of localised subsoil loosening on crop performance and selected soil attributes. Control plots consisted of disk ploughing; the implemented treatments were conventional deep-ripping and localised slotting below the planting line. A crop rotation consisting of a legume followed by maize was established annually to assess the impact of these treatments on crop performance. In the control treatment, root development was restricted to the topsoil (0–20 cm) due to high subsoil bulk density (>1.6 Mg m⁻³). After deep-ripping, no improvement was observed in bulk density, rooting depth and in crop performance. The implementation of a slotting treatment systematically improved root development in the slotted subsoil, root impact frequency increasing from <0.2 to 0.6–0.8 (P = 0.01) despite no change in the bulk densities of the subsoil. This systematic improvement in root development could be explained by (i) reduced slumping that enable root development prior to recompaction and/or (ii) preferential drainage in the slot and therefore decreased resistance to root penetration. In a dry year maize yield was improved by 78% (P = 0.01); the deep-rooting legume Stylosanthes was tested only a wet year and its biomass production increased by >40% (P = 0.03). This study highlights the detrimental impact of subsoil compaction on root development and the potential role of slotting in coarse textured soils as a long-term management tool in addressing adverse subsoil physical characteristics that limit deep-rooting.     

Utilization of near infrared reflectance spectroscopy (NIRS) to quantify the impact of earthworms on soil and carbon erosion in steep slope ecosystem: A study case in Northern Vietnam

This work focuses on a new approach to quantify the effects of above-ground earthworm's activity on soil erosion in steep slope ecosystems such as in Northern Vietnam. In these areas and in many others in the world, soil erosion becomes a major issue while the factors that determine it are still misunderstood. Earthworm's activity is believed to influence soil erosion rate, but we are still unable to precisely quantify their contribution to soil erosion. In this study, we used Near Infrared Reflectance Spectroscopy (NIRS) to quantify the proportion of soil aggregate in eroded soil coming from earthworm activity. This was done by generating NIRS signatures corresponding to different soil surface aggregates (above-ground soil casts produced by earthworms vs. surrounding topsoil).     

Assessment of cocoa input needs using soil types and soil spectral analysis

In this study, diffuse reflectance spectroscopy (DRS) approach was examined for making input recommendations in the smallholder cocoa farms of Papua New Guinea (PNG). Soil samples were collected from four provinces of PNG. Soil samples from four different depths (0–10, 10–30, 30–60 and 60–90 cm) of 32 profiles in each of these site were used to create a database of soil chemical and physical properties. Spectral reflectance values at 1 nm interval covering visible to shortwave‐infrared (350–2,500 nm) were collected for each of these soil samples to develop partial least squares regression models. Soil textural fractions, soil organic carbon contents and available N were well predicted by the DRS approach with R² values larger than 0.75. Moderate to poor estimation efficiencies were observed for remaining parameters. Nevertheless, the estimated soil attributes and their corresponding measured soil parameters were used as inputs to an input recommendation model of soil diagnosis to create input recommendation for a targeted cocoa yield of 1,000 kg dry cocoa beans ha^‐1 Resulting input recommendations were similar for both of these input sources (measured and DRS‐estimated) suggesting that the DRS approach may provide an easy way to create input recommendations.     

Topography of the casein micelle surface by surface plasmon resonance (SPR) using a selection of specific monoclonal antibodies

Several theoretical models of the casein micelle structure have been proposed in the past, but the exact organization of the four individual caseins (α(s1), α(s2), β, and κ) within this supramolecular structure remains unknown. The present study aims at determining the topography of the casein micelle surface by following the interaction between 44 monoclonal antibodies specific for different epitopes of α(s1)-, α(s2)-, β-, and κ-casein and the casein micelle in real time and no labeling using a surface plasmon resonance (SPR)-based biosensor. Although the four individual caseins were found to be accessible for antibody binding, data confirmed that the C-terminal extremity of κ-casein was highly accessible and located at the periphery of the structure. When casein micelles were submitted to proteolysis, the C-terminal extremity of κ-casein was rapidly hydrolyzed. Disintegration of the micellar structure resulted in an increased access for antibodies to hydrophobic areas of α(s1)- and α(s2)-casein.     

Identification and mapping of random amplified polymorphic DNA markers linked to a rhizomania resistance gene in sugar beet (Beta vulgaris L.) by bulked segregant analysis

Bulked segregant analysis was employed to identify random amplified polymorphic DNA (RAPD) markers linked to a gene that confers rhizomania resistance to a sugar beet line created from a Holly Sugar Company breeding population (USA). Polymorphism revealed with 160 arbitrary 10-mer oligonucleotide primers was screened in two bulks produced by separately pooling the individual DNAs from the six most resistant and the six most susceptible plants of an F₂ population segregating for rhizomania resistance. A study of the F₂ individuals showed that 19 primers generated 44 polymorphic markers which were then grouped into nine linkage groups. By analysis of variance, 12 were shown to have a significant effect upon the level of resistance and were mapped on a segment 22.3 cM long. A quantitative trait locus (QTL) of resistance was identified and located in a 4.6cM interval between two markers. It accounted for 67.4% of the observed variation and almost all the genetic variation. These results suggest that the identified QTL corresponds to a unique major gene conditioning the Holly resistance studied, which we have named Rz-l.     

Variation and phylogeny of the ribosomal DNA unit types and 5 S DNA inPetunia Jussieu

Summary Seven wildPetunia species including 2n = 18 species (P. parviflora Jussieu,P. linearis Hook.) and those with 2n = 14 (P. parodii Steene,P. axillaris Lam.,P. integrifolia Hook.,P. inflata R.E. Fries,P. violacea Lindl.) and tenPetunia hybrida horticultural lines were compared for polymorphisms in rDNA genes using the four restriction enzymesEcoRI,BamHI,HindIII andXhoI. All the unit types found in the lines pre-existed in the wild forms. There are two different sizes of either 11.45 or 11.6 kb./The 2n = 18 species are closely related to the 2n = 14 species, thus making thePetunia genus homogeneous. Moreover, it is likely thatP. hybrida lines originated in several kinds of crosses between these species. We constructed a dendrogram for all the 15 rDNA unit types found. Two main branches of the tree result from the presence or the absence ofHindIII sites. The main branch is divided according to variability at theEcoRI andBamHI sites. Taking into account the existence of several loci which carry one unit type only, we consider whether or not exchanges might occur between loci. Lines carrying two unit types and lines carrying three unit types support such a hypothesis.XhoI andBamHI fragments enable us to distinguish two types of 5S DNA corresponding to 2n = 18 and 2n = 14 species, respectively.P. hybrida lines and each 2n = 14 wild species carry one of the types only, that corresponds to one 5S DNA locus. The most parsimonious phylogenetic trees whatever the species chosen as the outgroup, do not fit with our knowledge ofPetunia and with taxonomy. This is likely because only few loci formed the basis of these phylogenetic constructions.     

Near infrared reflectance spectroscopy (NIRS) could be used for characterization of soil nematode community

Studying soil nematofauna provides useful information on soil status and functioning but requires high taxonomic expertise. Near infrared reflectance (NIR) spectroscopy (NIRS) has been reported to allow fast and inexpensive determination of numerous soil attributes. Thus the present study aimed at assessing the potential of NIRS for determining the abundance and diversity of soil nematodes in a set of 103 clayey topsoil samples collected in 2005 and 2006 from agricultural soils in the highlands of Madagascar.The morphological characterization of soil nematofauna involved extraction through elutriation then counting under binoculars and identification at family or genus level using microscopy, on ca. 150-g fresh soil samples. Taxa were assigned to five trophic groups, namely bacterial feeders, fungal feeders, obligate plant feeders, facultative plant feeders, and omnivores and predators (together). In addition, four ecological indexes were calculated: the Enrichment index, Structure index, Maturity index, and Plant parasitic index.Oven-dried (40 °C) < 2-mm sieved 5-g soil subsamples were scanned in the NIR range (1100-2500 nm), then spectra were fitted to nematofauna data using partial least square regression. Depending on the sample set considered (year 2005, year 2006, or both years), NIRS prediction of total nematode abundance was accurate (ratio of standard deviation to standard error of cross validation, i.e. RPD ≥ 2) or acceptable (RPD ≥ 1.6). Predictions were accurate, acceptable, or quasi-acceptable (RPD ≥ 1.4) for several of the six most abundant taxa, and to a larger extent, for most trophic groups (except facultative plant feeders); but they could not be made for taxa present in a small number of samples or at low abundance. By contrast, NIRS prediction of relative abundances (in proportion of total abundance) was poor in general, as was also the prediction of ecological indexes (except for the 2006 set). On the whole, these results were less accurate than NIRS predictions of soil attributes often reported in the literature. However, though not very accurate, NIRS predictions were worthwhile considering the labor-intensity of the morphological characterization. Most of all, NIRS analyses were carried out on subsamples that were probably too small (5 g) to allow representative sampling of nematofauna. Using larger samples for NIRS (e.g. 100 g) would likely result in more accurate predictions, and is therefore recommended. Scanning un-dried samples could also help improve prediction accuracy, as morphological characterization was carried out on samples not dried after sampling.Examining wavelengths that contributed most to NIRS predictions, and chemical groups they have been assigned to, suggested that NIRS predictions regarding nematofauna depended on constituents of both nematodes and preys’ food. Predictions were thus based on both nematofauna and soil organic properties reflected by nematofauna.     

Quantification of vertical solid matter transfers in soils during pedogenesis by a multi-tracer approach

Purpose

Vertical transfer of solid matter in soils (bioturbation and translocation) is responsible for changes in soil properties over time through the redistribution of most of the soil constituents with depth. Such transfers are, however, still poorly quantified.

Materials and methods

In this study, we examine matter transfer in four eutric Luvisols through an isotopic approach based on ¹³⁷Cs, ²¹⁰Pb_(xs), and meteoric ¹⁰Be. These isotopes differ with respect to chemical behavior, input histories, and half-lives, which allows us to explore a large time range. Their vertical distributions were modeled by a diffusion-advection equation with depth-dependent parameters. We estimated a set of advection and diffusion coefficients able to simulate all isotope depth distributions and validated the resulting model by comparing the depth distribution of organic carbon (including ^12/13C and ¹⁴C isotopes) and of the 0–2-μm particles with the data.

Results and discussion

We showed that (i) the model satisfactorily reproduces the organic carbon, ¹³C, and ¹⁴C depth distributions, indicating that organic carbon content and age can be explained by transport without invoking depth-dependent decay rates; (ii) translocation partly explains the 0–2-μm particle accumulation in the Bt horizon; and (iii) estimates of diffusion coefficients that quantify the soil mixing rate by bioturbation are significantly higher for the studied plots than those obtained by ecological studies.

Conclusions

This study presents a model capable of satisfactorily reproducing the isotopic profiles of several tracers and simulating the distribution of organic carbon and the translocation of 0–2-μm particles.

     

Resveratrol inhibits the activity of equine neutrophil myeloperoxidase by a direct interaction with the enzyme

Resveratrol is a polyphenolic antioxidant present in beverage and food known for its multiple protective effects. We report the inhibitory effects of resveratrol on equine myeloperoxidase (MPO), a hemic peroxidase present in the granules of the neutrophils involved in the inflammatory response. Resveratrol inhibited the production of reactive oxygen species (ROS) by stimulated equine neutrophils by acting as a direct scavenger of the ROS released by the cells but did not modify the degranulation of the stimulated neutrophils as the amounts of released MPO were unchanged. Resveratrol strongly inhibited the chlorination, oxidation, and nitration activities of MPO in a dose-dependent manner. By an original technique of specific immunological extraction followed by enzymatic detection (SIEFED), we demonstrated that resveratrol inhibited the peroxidasic activity of the MPO measured by a direct interaction such as the fixation of resveratrol on the enzyme. The observation of a decrease of the accumulation of compound II suggested that resveratrol acts as an electron donor for MPO reduction.