Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Foams and air-water interfaces stabilised by mildly purified rapeseed proteins after defatting
    Yang, Jack ; Faber, Iris ; Berton-Carabin, Claire C. ; Nikiforidis, Constantinos V. ; Linden, Erik van der; Sagis, Leonard M.C. - \ 2021
    Food Hydrocolloids 112 (2021). - ISSN 0268-005X
    Atomic force microscopy - Foam - Lissajous plots - Oleosomes - Rapeseed proteins - Surface rheology

    Rapeseed protein isolate has promising functional properties (e.g. emulsifying and foaming), but is often extracted with intensive purification steps. This requires a considerable use of resources and damages protein functionality regarding, for instance, foam stabilization. We studied the interfacial and foaming properties of a mildly obtained rapeseed protein concentrate that contained oleosomes, and of its derived defatted rapeseed protein concentrate after solvent-based defatting. The air-water interfaces were deformed with large amplitude dilatational and shear deformations, which were analysed with Lissajous plots. At low bulk concentrations (0.01% w/w), the rapeseed protein-stabilised interfaces behaved as viscoelastic solids. The interfacial films became weaker and more stretchable at higher concentrations, suggesting that more non-protein components interfere with the intermolecular interactions between the adsorbed proteins at higher bulk concentrations. We confirmed the presence of such non-protein components at the interface by analysing Langmuir-Blodgett films with atomic force microscopy. The stability and air bubble size of foams prepared with either rapeseed protein concentrate or defatted rapeseed protein concentrate were similar. Mild purification of rapeseed resulted in a protein concentrate containing lipids in their native oleosome form, which have a minor destabilizing effect on foams. We conclude that mild purification is a suitable method to obtain sustainably produced protein concentrates with promising foaming properties.

    Physicochemical evaluation and Fourier transform infrared spectroscopy characterization of quality protein maize starch subjected to different modifications
    Awolu, Olugbenga Olufemi ; Odoro, Joshua Wisdom ; Adeloye, Jumoke Bukola ; Lawal, Oluranti Mopelola - \ 2020
    Journal of Food Science (2020). - ISSN 0022-1147
    FTIR - Modification - pasting properties - Quality Protein Maize - Starch

    Abstract: Quality protein maize (QPM) is a biofortified maize rich in lysine and tryptophan, essential amino acids required in human nutrition. This research therefore characterizes native and modified starches from QPM by evaluating the physicochemical properties, Fourier transform infrared spectra (FTIR), and pasting properties. The native QPM starch was modified by oxidation, acetylation, pregelatinization, and acid thinning techniques. The starch yield of native QPM was 43.80%, while that of modified starches were from 88.22 to 98.34%. The moisture content of the native and modified starches was from 4.56 to 9.20 g/100g. Modifications significantly (P ≤ 0.05) reduced the lipid, protein, and amylose contents of the QPM. While the native starch had 0.72 g/cm3 bulk density, modified starches were between 0.59 and 0.88 g/cm3; chemical modification reduced the bulk density and physical modification increased it. In addition, all the modifications except oxidation significantly (P ≤ 0.05) increased water absorption capacity. The oil absorption of the starch samples was increased by modification techniques used with the exception of physical modification. Chemical modification reduced the viscosity of QPM starch while physical modification increased it. The reducing sugar content of the starch was reduced by both the physical and chemical starch modification techniques. Acetylated sample exhibited the highest swelling power while acid-thinned sample had the least. The major functional groups identified via FTIR were OH, C-H, C=H, and C≡H. Modifications did not affect the functional groups as all the native and modified starches (except oxidized sample) all have similar spectrum and bands stretch. Practical Application: The study contributes to existing knowledge on valorization of modified starch from quality protein maize. Profiling the chemical attributes of modified starches is especially valuable in novel food processing techniques.

    Evaluation of PBN spin-trapped radicals as early markers of lipid oxidation in mayonnaise
    Merkx, Donny W.H. ; Plankensteiner, Lorenz ; Yu, Yafei ; Wierenga, Peter A. ; Hennebelle, Marie ; Duynhoven, John P.M. van - \ 2020
    Food Chemistry 334 (2020). - ISSN 0308-8146
    H NMR - Bulk oil - ESR - Lipid oxidation - Mayonnaise - MNP-L - PBN

    Quality deterioration of mayonnaise is caused by lipid oxidation, mediated by radical reactions. Assessment of radicals would enable early lipid oxidation assessment and generate mechanistic insights. To monitor short-lived lipid-radicals, N-tert-butyl-α-phenylnitrone (PBN), a spin-trap, is commonly used. In this study, the fate of PBN-adducts and their impact on lipid oxidation mechanisms in mayonnaise were investigated. The main signals detected by Electron Spin Resonance (ESR) were attributed to L[rad]-radicals attached to 2-methyl-2-nitrosopropane (MNP), one of three degradation products of the PBN-peroxy-adduct. The second degradation product, benzaldehyde, was detected with Nuclear Magnetic Resonance (1H NMR), in line with MNP-L adduct generation. For the third class of degradation products, LO[rad]-radicals, their scission products were detected with 1H NMR and indicated that LO[rad]-radicals have a major impact on downstream oxidation pathways. This precludes mechanistical studies in presence of PBN. Degradation products of PBN-adducts can, however, be used for early assessment of antioxidants efficacy in oil-in-water emulsions.

    Biases in bulk: DNA metabarcoding of marine communities and the methodology involved
    Loos, Luna M. van der; Nijland, Reindert - \ 2020
    Molecular Ecology (2020). - ISSN 0962-1083
    biodiversity - DNA metabarcoding - marine monitoring - technical biases

    With the growing anthropogenic pressure on marine ecosystems, the need for efficient monitoring of biodiversity grows stronger. DNA metabarcoding of bulk samples is increasingly being implemented in ecosystem assessments and is more cost-efficient and less time-consuming than monitoring based on morphology. However, before raw sequences are obtained from bulk samples, a profound number of methodological choices must be made. Here, we critically review the recent methods used for metabarcoding of marine bulk samples (including benthic, plankton and diet samples) and indicate how potential biases can be introduced throughout sampling, preprocessing, DNA extraction, marker and primer selection, PCR amplification and sequencing. From a total of 64 studies evaluated, our recommendations for best practices include to (a) consider DESS as a fixative instead of ethanol, (b) use the DNeasy PowerSoil kit for any samples containing traces of sediment, (c) not limit the marker selection to COI only, but preferably include multiple markers for higher taxonomic resolution, (d) avoid touchdown PCR profiles, (e) use a fixed annealing temperature for each primer pair when comparing across studies or institutes, (f) use a minimum of three PCR replicates, and (g) include both negative and positive controls. Although the implementation of DNA metabarcoding still faces several technical complexities, we foresee wide-ranging advances in the near future, including improved bioinformatics for taxonomic assignment, sequencing of longer fragments and the use of whole-genome information. Despite the bulk of biases involved in metabarcoding of bulk samples, if appropriate controls are included along the data generation process, it is clear that DNA metabarcoding provides a valuable tool in ecosystem assessments.

    Eucalyptus and alder field margins differ in their impact on ecosystem services and biodiversity within cropping fields of the Peruvian Andes
    Visscher, Anna M. ; Vanek, Steven ; Meza, Katherin ; Goede, Ron G.M. de; Valverde, Amador A. ; Ccanto, Raul ; Olivera, Edgar ; Scurrah, Maria ; Fonte, Steven J. - \ 2020
    Agriculture, Ecosystems and Environment 303 (2020). - ISSN 0167-8809
    Alnus - Erosion control - Eucalyptus - Ground vegetation - Hedgerows - Nutrient provision - Peru - Pest control - Soil macrofauna - Soil organic matter - Solanum tuberosum

    Intensified rotations and increased reliance on agrochemical inputs in many parts of the Andean highlands generate concern for soil health, biodiversity, and key ecosystem functions that are essential for maintaining agricultural productivity and the well-being of smallholder communities throughout the region. Improved management of perennial vegetation within field margins represents a promising option currently being explored in many Andean communities, with the potential to better design these field margins to support multiple ecosystem services (ES). In this study we examined the effect of two types of common woody perennial field margins (eucalyptus vs. alder) on crop production and other soil-based ES at variable distances from the field edge. Sampling was conducted in twenty potato fields, ten with borders dominated by alder trees (Alnus acuminata) and another ten with eucalyptus (Eucalyptus globulus). Within each field, transects (∼10 m) were established with six sampling points extending from the perennial field margins towards the center of the production field. At each point, a suite of ES was assessed including: nutrient provision (based on levels of SOM, pH, P, K, and N in the soil), biodiversity maintenance (ground vegetation and soil macrofauna), erosion control (infiltration, aggregation, bulk density), bio-control (occurrence of common crop pests/pathogens and predators) and crop production (potato yields and quality). The provision of ES was generally found to be higher in the field margins than in the arable fields. The dominant tree species in the field margin was also important, such that fields bordered by alder trees showed higher SOM, macrofauna diversity and aggregate stability compared to those bordered by eucalyptus trees. Fields bordered by eucalyptus trees showed higher values for overall vegetation diversity, pH and available phosphorus. While potato yields did not differ between fields bordered by alder vs. eucalyptus, potato pest pressure was higher in fields bordered by eucalyptus trees. Our findings suggest that improved management of perennial field margins can enhance the provision of multiple ES in agricultural landscapes of the Peruvian highlands.

    Contributions of viscosity and friction properties to oral and haptic texture perception of iced coffees
    Blok, Annelies E. ; Bolhuis, Dieuwerke P. ; Stieger, Markus - \ 2020
    Food & Function 11 (2020)7. - ISSN 2042-6496 - p. 6446 - 6457.

    Creaminess is affected by bulk properties (i.e. viscosity) and surfaces properties (i.e. friction). This study aimed (i) to assess contributions of viscosity and friction properties to creaminess, thickness and slipperiness perception; and (ii) to compare oral and haptic thickness and slipperiness perception of iced coffees. Three iced coffees differing in viscosity and friction properties were prepared: low viscosity - high friction (LV-HF); low viscosity - low friction (LV-LF) and high viscosity - low friction (HV-LF) iced coffee. Viscosity of iced coffees was adjusted by addition of maltodextrin, and viscosity of HV-LF was 2.5 times higher than that of LV-HF and LV-LF (10 vs. 4 mPa s at 100 s-1). Friction coefficients of LV-LF were reduced by addition of polyethylene glycol (PEG, Mw 6000), and were up to 25% lower than those of LV-HF. Forty-seven untrained panellists (18-27 years) performed two-alternative forced choice (2-AFC) and rank-rating tests to compare creaminess by oral assessment, and thickness and slipperiness by oral and haptic assessment. Results from 2-AFC and rank-rating congruently showed that HV-LF was creamier, thicker and more slippery than LV-HF and LV-LF, both orally and haptically. LV-LF was orally perceived as less creamy and less thick, but haptically as more slippery than LV-HF. Creaminess was more strongly correlated to thickness than to slipperiness. Oral and haptic evaluation of thickness was congruent, whereas differences between oral and haptic slipperiness evaluation were product-dependent. We conclude that increasing viscosity enhances creaminess, whereas increasing lubrication is not necessarily sufficient to increase creaminess in iced coffees.

    All-aqueous emulsions as miniaturized chemical reactors in the food and bioprocess technology
    Madadlou, Ashkan ; Saggiomo, Vittorio ; Schroën, Karin ; Fogliano, Vincenzo - \ 2020
    Current Opinion in Food Science 33 (2020). - ISSN 2214-7993 - p. 165 - 172.
    All-aqueous emulsions are conventionally formed at bulk scale by mild shaking of aqueous two-phase systems. They can be used to carry out reactions both in droplets (compartmentalized) and on droplet surfaces in conditions free of synthetic surfactants and organic solvents. The use of all-aqueous emulsions for extractive bioconversion is a routine application; however, these emulsions hold many more promises. A renowned, rapidly evolving application is bio-microgel synthesis through biopolymer crosslinking within the emulsion internal phase. When polyelectrolyte crosslinking is achieved at the interface rather than in droplets, microcapsules can be formed, and when in situ colloidal particle generation at the droplet surface is obtained, colloidosomes are produced. The use of microfluidics to control the formation of all-aqueous emulsions offers many advantages in reactions monitoring and partitioning of reactants.
    Impact of plastic mulch film debris on soil physicochemical and hydrological properties
    Qi, Yueling ; Beriot, Nicolas ; Gort, Gerrit ; Huerta Lwanga, Esperanza ; Gooren, Harm ; Yang, Xiaomei ; Geissen, Violette - \ 2020
    Environmental Pollution 266 (2020). - ISSN 0269-7491
    Agricultural soil - Biodegradable plastic - Microplastics - Plastic pollution - Soil quality

    The plastic mulch films used in agriculture are considered to be a major source of the plastic residues found in soil. Mulching with low-density polyethylene (LDPE) is widely practiced and the resulting macro- and microscopic plastic residues in agricultural soil have aroused concerns for years. Over the past decades, a variety of biodegradable (Bio) plastics have been developed in the hope of reducing plastic contamination of the terrestrial ecosystem. However, the impact of these Bio plastics in agroecosystems have not been sufficiently studied. Therefore, we investigated the impact of macro (around 5 mm) and micro (<1 mm) sized plastic debris from LDPE and one type of starch-based Bio mulch film on soil physicochemical and hydrological properties. We used environmentally relevant concentrations of plastics, ranging from 0 to 2% (w/w), identified by field studies and literature review. We studied the effects of the plastic residue on a sandy soil for one month in a laboratory experiment. The bulk density, porosity, saturated hydraulic conductivity, field capacity and soil water repellency were altered significantly in the presence of the four kinds of plastic debris, while pH, electrical conductivity and aggregate stability were not substantially affected. Overall, our research provides clear experimental evidence that microplastics affect soil properties. The type, size and content of plastic debris as well as the interactions between these three factors played complex roles in the variations of the measured soil parameters. Living in a plastic era, it is crucial to conduct further interdisciplinary studies in order to have a comprehensive understanding of plastic debris in soil and agroecosystems.

    Bulk and interfacial properties of milk fat emulsions stabilized by whey protein isolate and whey protein aggregates
    Zhou, Xilong ; Sala, Guido ; Sagis, Leonard M.C. - \ 2020
    Food Hydrocolloids 109 (2020). - ISSN 0268-005X
    Bulk stability - Interfacial rheology - Recombined dairy cream - Whey protein (aggregate)

    Whey protein is widely used in the food industry as an emulsion stabilizer because of its outstanding emulsifying ability. Recent studies have shown that heat-induced whey protein aggregates may also have potential to stabilize emulsions. The interfacial behavior of whey protein and whey protein aggregates adsorbed at the milk fat-water interface has not been well investigated, especially not in the nonlinear regime, which is highly relevant for the preparation of products such as recombined dairy cream. In this study, the interfacial properties of milk fat-water interfaces stabilized by whey protein isolate (WPI) and whey protein aggregates (WPA) at different bulk concentrations (0.1 wt% - 4.0 wt%) were studied by Large Amplitude Oscillatory Dilatation (LAOD). Lissajous plots were used to analyse the nonlinear response of the interfaces as a function of strain amplitude and frequency. The elastic modulus was quantified based on the tangent modulus at zero instantaneous strain in expansion and in compression. Bulk stability of creams stabilized with the mentioned proteins was studied by determining creaming rate, droplet size distribution, ζ-potential and viscosity of the continuous phase. At low concentrations (<2.0 wt%), WPI-stabilized cream had smaller oil droplets than WPA-stabilized cream, indicating that at these concentrations WPI had better emulsifying ability. For concentrations higher than 2.0 wt%, WPA was a better emulsifier in terms of creaming stability because of the higher viscosity of the continuous phase of the emulsions. Both WPI and WPA could prevent coalescence equally well if the concentration was higher than 0.5 wt%. LAOD measurements showed that at a protein concentration of 0.1 wt%, there was little difference between WPI- and WPA-stabilized interfaces. At 4.0 wt%, WPI showed abrupt intra-cycle yielding followed by a predominantly viscous behavior at large expansion. The WPA interfacial layer had a larger maximum linear strain, and showed a more gradual softening in expansion and mild strain hardening in compression. We hypothesize that WPI formed denser and more brittle (quasi-) 2d structures at the interface, while the interfaces formed by WPA might have a thicker and more stretchable 3d structure. The WPA-stabilized emulsion was less resistant to coalescence upon drastic stirring, which can be explained with its different large deformation behavior, and is relevant for applications where the cream is subjected to large deformations (whipping or stirring).

    The origin and widespread occurrence of Sli-based self-compatibility in potato
    Clot, Corentin R. ; Polzer, Clara ; Prodhomme, Charlotte ; Schuit, Cees ; Engelen, Christel J.M. ; Hutten, Ronald C.B. ; Eck, Herman J. van - \ 2020
    Theoretical and Applied Genetics 133 (2020). - ISSN 0040-5752 - p. 2713 - 2728.

    Self-compatible (SC) diploid potatoes allow innovative potato breeding. Therefore, the Sli gene, originally described in S. chacoense, has received much attention. In elite S. tuberosum diploids, spontaneous berry set is occasionally observed. We aimed to map SC from S. tuberosum origin. Two full-sib mapping populations from non-inbred diploids were used. Bulks were composed based on both pollen tube growth and berry set upon selfing. After DNA sequencing of the parents and bulks, we generated k-mer tables. Set algebra and depth filtering were used to identify bulk-specific k-mers. Coupling and repulsion phase k-mers, transmitted from the SC parent, mapped in both populations to the distal end of chromosome 12. Intersection between the k-mers from both populations, in coupling phase with SC, exposed a shared haplotype of approximately 1.5 Mb. Subsequently, we screened read archives of potatoes and wild relatives for k-mers specific to this haplotype. The well-known SC clones US-W4 and RH89-039-16, but surprisingly, also S. chacoense clone M6 were positives. Hence, the S. tuberosum source of SC seems identical to Sli. Furthermore, the candidate region drastically reduced to 333 kb. Haplotype-specific KASP markers were designed and validated on a panel of diploid clones including another renown SC dihaploid G254. Interestingly, k-mers specific to the SC haplotype were common in tetraploid varieties. Pedigree information suggests that the SC haplotype was introduced into tetraploid varieties via the founder “Rough Purple Chili”. We show that Sli is surprisingly widespread and indigenous to the cultivated gene pool of potato.

    Potato Yield and Yield Components as Affected by Positive Selection During Several Generations of Seed Multiplication in Southwestern Uganda
    Priegnitz, Uta ; Lommen, Willemien J.M. ; Vlugt, René A.A. van der; Struik, Paul C. - \ 2020
    Potato Research (2020). - ISSN 0014-3065
    Multi-seasonal trials - Positive selection - Seed degeneration - Seed potatoes - Seed regeneration - Uganda - Yield increase

    Potato (Solanum tuberosum L.) is an important crop in Uganda but production is low. There is not a well-functioning official seed system and farmers use potato tubers from a previous harvest as seed. This study investigated how effectively the seed technology positive selection enhanced yield and underlying crop characteristics across multiple seasons, compared to the farmers’ selection method. Positive selection is selecting healthy plants during crop growth for harvesting seed potato tubers to be planted in the next season. Farmers’ selection involves selection of seed tubers from the bulk of the ware potato harvest. Positive selection was compared to farmers’ seed selection for up to three seasons in three field trials in different locations in southwestern Uganda using seed lots from different origins. Across all experiments, seasons and seed lots, yields were higher under positive selection than under farmers’ selection. The average yield increase resulting from positive selection was 12%, but yield increases were variable, ranging from − 5.7% to + 36.9%, and in the individual experiments often not significant. These yield increases were due to higher yields per plant, and mostly higher weights per tuber, whereas the numbers of tubers per plant were not significantly different. Experimentation and yield assessment were hampered by a varying number of plants that could not be harvested because plants had to be rogued from the experimental plots because of bacterial wilt (more frequent under farmers’ selection than under positive selection), plants disappeared from the experimental field and sometimes plants did not emerge. Nevertheless, adoption of positive selection should be encouraged due to a higher production and less virus infection of seed tubers in positive selected plants, resulting in a lower degeneration rate of potato seed tubers.

    Spatiotemporal Heterogeneity of κ-Carrageenan Gels Investigated via Single-Particle-Tracking Fluorescence Microscopy
    Martens, Koen J.A. ; Duynhoven, John Van; Hohlbein, Johannes - \ 2020
    Langmuir 36 (2020)20. - ISSN 0743-7463 - p. 5502 - 5509.

    Hydrogels made of the polysaccharide κ-carrageenan are widely used in the food and personal care industry as thickeners or gelling agents. These hydrogels feature dense regions embedded in a coarser bulk network, but the characteristic size and behavior of these regions have remained elusive. Here, we use single-particle-tracking fluorescence microscopy (sptFM) to quantitatively describe κ-carrageenan gels. Infusing fluorescent probes into fully gelated κ-carrageenan hydrogels resulted in two distinct diffusional behaviors. Obstructed self-diffusion of the probes revealed that the coarse network consists of κ-carrageenan strands with a typical diameter of 3.2 ± 0.3 nm leading to a nanoprobe diffusion coefficient of ∼1-5 × 10-12 m2/s. In the dense network regions, we found a fraction with a largely decreased diffusion coefficient of ∼1 × 10-13 m2/s. We also observed dynamic exchange between these states. The computation of spatial mobility maps from the diffusional data indicated that the dense network regions have a characteristic diameter of ∼1 μm and show mobility on the second-to-minute timescale. sptFM provides an unprecedented view of spatiotemporal heterogeneity of hydrogel networks, which we believe bears general relevance for understanding transport and release of both low- and high-molecular weight solutes.

    Dietary Isomalto/Malto-Polysaccharides Increase Fecal Bulk and Microbial Fermentation in Mice
    Mistry, Rima H. ; Borewicz, Klaudyna ; Gu, Fangjie ; Verkade, Henkjan J. ; Schols, Henk A. ; Smidt, Hauke ; Tietge, Uwe J.F. - \ 2020
    Molecular Nutrition & Food Research 64 (2020)12. - ISSN 1613-4125
    bile acids - cholesterol - IMMP - microbiota - polysaccharides - prebiotics - short-chain fatty acids

    Scope: The prevalence of metabolic-syndrome-related disease has strongly increased. Nutritional intervention strategies appear attractive, particularly with novel prebiotics. Isomalto/malto-polysaccharides (IMMPs) represent promising novel prebiotics that promote proliferation of beneficial bacteria in vitro. The present study investigates for the first time the in vivo effects of IMMP in mice. Methods and results: C57BL/6 wild-type mice received control or IMMP-containing (10%, w/w) diets for 3 weeks. IMMP leads to significantly more fecal bulk (+26%, p < 0.05), higher plasma non-esterified fatty acids (colorimetric assay, +10%, p < 0.05), and lower fecal dihydrocholesterol excretion (mass spectrometry, −50%, p < 0.05). Plasma and hepatic lipid levels (colorimetric assays following lipid extraction) are not influenced by dietary IMMP, as are other parameters of sterol metabolism, including bile acids (gas chromatography/mass spectrometry). IMMP is mainly fermented in the cecum and large intestine (high-performance anion exchange chromatography). Next-generation sequencing demonstrates higher relative abundance of Bacteroides and butyrate producers (Lachnospiraceae, Roseburia Odoribacter) in the IMMP group. Conclusion: The combined results demonstrate that IMMP administration to mice increases fecal bulk and induces potentially beneficial changes in the intestinal microbiota. Further studies are required in disease models to substantiate potential health benefits.

    Litter cover promotes biocrust decomposition and surface soil functions in sandy ecosystem
    Wu, Gao Lin ; Zhang, Meng Qi ; Liu, Yu ; López‐Vicente, Manuel - \ 2020
    Geoderma 374 (2020). - ISSN 0016-7061
    Ecological restoration - Sandy ecosystem - Soil crust - Soil nutrient - Soil organic matter - Soil particle size

    Ecological restoration of sandy inland ecosystems is important for achieving global sustainability. In the world's semi-arid regions, soil crusts play crucial roles in maintaining ecosystem functioning. However, the true extent of soil quality improvement during the development of crusts is an issue not solved. In this study, four development stages of natural soil crusts, i.e., physical crusts (PC), biocrusts (BC), litter covered biocrusts (LBC) and litter crusts (LC) were selected in a semi-arid sandy ecosystem, along with a bare sandy land (BSL) as control area, to evaluate soil physicochemical properties at different soil depths. The coverage of litter (mainly leaves of Populus simonii) increased soil moisture and reduced soil bulk density. Compared with BC, the content of total soil organic matter (SOM) decreased in LBC by 13.83% and increased in LC by 36.57%. In contrast with BC, LC promoted a significant increase in soil nutrients, such as total nitrogen (30.30%), total phosphorus (46.89%) and available potassium (34.40%) in the topsoil layer (0–2 cm). Besides, LC contained higher clay and silt contents (10.47% and 29.81%) and lower sand content (−1.02%) than BC. In the 0–10 cm soil layer, the D (fractal dimension of the soil particle size distribution) of LC was the largest, with a value 5.71%, 6.1%, 2.44% and 0.93% higher than D in BSL, PC, BC and LBC, respectively. These findings reveal that litter covering facilitate the disintegration of BC, which further forms LC, and these processes clearly promote the enhancement of soil quality under sandy semi-arid conditions. Our findings are particularly important for predicting the transformation processes of sandy soil crusts and are of interest in ecological restoration programs.

    Trafficking intensity index for soil compaction management in grasslands
    Bondi, Giulia ; O‘Sullivan, Lilian ; Fenton, Owen ; Creamer, Rachel ; Marongiu, Irene ; Wall, David P. - \ 2020
    Soil Use and Management (2020). - ISSN 0266-0032
    compaction - grazing - machinery - soil - soil structural quality - trafficking pressure

    Good soil structure provides multiple benefits for society but in grass-based production systems is underpinned by trafficking management regime. For Irish soils, there is no soil trafficking intensity index that considers the effect of geo-climatic variability or differences in drainage classes on soil compaction risk. Grazing and machinery activity data were compiled across 38 managed grasslands along with common soil structural quality indicators in order to develop and validate a ‘soil trafficking intensity index for compaction (STICi)’. Two component indices of STICi were developed: (a) a grazing trafficking index (Gi, kg × year ha−1) and (b) a machinery trafficking index (Mi, kg × year ha−1). The average annual grazing trafficking pressure observed was 213,914 kg × year ha−1, and the average annual machinery trafficking pressure was 4,412 kg × year ha−1. These figures represent thresholds above which soils are at higher risk of compaction. Mi spanned a wider range (−2.1 ≤ Mi ≤ 2.8) compared with Gi (−1.32 ≤ Gi ≤ 1.06). STICi and components, when disaggregated by soil drainage class, were able to detect changes in direct indicators of soil structural quality, such as bulk density, total porosity, water holding capacity, water conductivity and visual soil assessment. STICi (Mi and Gi) were also related to indirect indicators, such as, soil carbon content, earthworms and microbial biomass. In general, poorly drained sites showed higher vulnerability to machinery trafficking intensity compared with grazing trafficking pressure. At national scale, STICi can be utilized to identify soils at risk of compaction and underpin targeted management advice for supporting sustainable grassland production.

    Disinfection exhibits systematic impacts on the drinking water microbiome
    Dai, Zihan ; Sevillano-Rivera, Maria C. ; Calus, Szymon T. ; Bautista-De Los Santos, Q.M. ; Eren, A.M. ; Wielen, Paul W.J.J. Van Der; Ijaz, Umer Z. ; Pinto, Ameet J. - \ 2020
    Microbiome 8 (2020)1. - ISSN 2049-2618
    Disinfection - Drinking water microbiome - Metagenomics - Selection

    Limiting microbial growth during drinking water distribution is achieved either by maintaining a disinfectant residual or through nutrient limitation without using a disinfectant. The impact of these contrasting approaches on the drinking water microbiome is not systematically understood. We use genome-resolved metagenomics to compare the structure, metabolic traits, and population genomes of drinking water microbiome samples from bulk drinking water across multiple full-scale disinfected and non-disinfected drinking water systems. Microbial communities cluster at the structural- and functional potential-level based on the presence/absence of a disinfectant residual. Disinfectant residual alone explained 17 and 6.5% of the variance in structure and functional potential of the drinking water microbiome, respectively, despite including multiple drinking water systems with variable source waters and source water communities and treatment strategies. The drinking water microbiome is structurally and functionally less diverse and variable across disinfected compared to non-disinfected systems. While bacteria were the most abundant domain, archaea and eukaryota were more abundant in non-disinfected and disinfected systems, respectively. Community-level differences in functional potential were driven by enrichment of genes associated with carbon and nitrogen fixation in non-disinfected systems and γ-aminobutyrate metabolism in disinfected systems likely associated with the recycling of amino acids. Genome-level analyses for a subset of phylogenetically-related microorganisms suggests that disinfection selects for microorganisms capable of using fatty acids, presumably from microbial decay products, via the glyoxylate cycle. Overall, we find that disinfection exhibits systematic selective pressures on the drinking water microbiome and may select for microorganisms able to utilize microbial decay products originating from disinfection-inactivated microorganisms. [MediaObject not available: see fulltext.]

    Estimating turbulent fluxes in the tropical andes
    Córdova, Mario ; Bogerd, Linda ; Smeets, Paul ; Carrillo-Rojas, Galo - \ 2020
    Atmosphere 11 (2020)2. - ISSN 2073-4433
    Andes - Eddy covariance - Latent heat flux - Paramo - Penman-monteith - Sensible heat flux - Tropics - Turbulent fluxes - Zhurucay ecohydrological observatory

    The correct estimation of Sensible Heat Flux (H) and Latent Heat Flux (LE) (i.e., turbulent fluxes) is vital in the understanding of exchange of energy and mass among hydrosphere, atmosphere, and biosphere in an ecosystem. One of the most popular methods to measure these fluxes is the Eddy Covariance (EC) technique; however, there are a number of setbacks to its application, especially in remote and topographically complex terrain such as the higher altitudes of the Andes. Efforts have been made by the scientific community to parameterise these fluxes based on other more commonly measured variables. One of the most widespread methods is the so-called bulk method, which relates average temperature, humidity, and wind vertical profiles to the turbulent fluxes. Another approach to estimate LE is the Penman-Monteith (PM) equation which uses meteorological measurements at a single level. The objective of this study was to validate these methods for the first time in the Tropical Andes in Southern Ecuador (in the paramo ecosystem at 3780 m a.s.l.) using EC and meteorological measurements. It was determined that the bulk method was the best to estimate H, although some adjustments had to be made to the typical assumptions used to estimate surface meteorological values. On the other hand, the PM equation yielded the best LE estimations. For both fluxes, the error in the estimations was within the uncertainty range of the EC measurements. It can be concluded that it is possible to accurately estimate H and LE using the methods described in this paper in this ecosystem when no direct measurements are available.

    Substitution of manure for chemical fertilizer affects soil microbial community diversity, structure and function in greenhouse vegetable production systems
    Luan, Haoan ; Gao, Wei ; Huang, Shaowen ; Tang, Jiwei ; Li, Mingyue ; Zhang, Huaizhi ; Chen, Xinping ; Masiliūnas, Dainius - \ 2020
    PLoS ONE 15 (2020)2. - ISSN 1932-6203

    Soil microbial communities and enzyme activities together affect various ecosystem functions of soils. Fertilization, an important agricultural management practice, is known to modify soil microbial characteristics; however, inconsistent results have been reported. The aim of this research was to make a comparative study of the effects of different nitrogen (N) fertilizer rates and types (organic and inorganic) on soil physicochemical properties, enzyme activities and microbial attributes in a greenhouse vegetable production (GVP) system of Tianjin, China. Results showed that manure substitution of chemical fertilizer, especially at a higher substitution rate, improved soil physicochemical properties (higher soil organic C (SOC) and nutrient (available N and P) contents; lower bulk densities), promoted microbial growth (higher total phospholipid fatty acids and microbial biomass C contents) and activity (higher soil hydrolase activities). Manure application induced a higher fungi/bacteria ratio due to a lower response in bacterial than fungal growth. Also, manure application greatly increased bacterial stress indices, as well as microbial communities and functional diversity. The principal component analysis showed that the impact of manure on microbial communities and enzyme activities were more significant than those of chemical fertilizer. Furthermore, redundancy analysis indicated that SOC and total N strongly influenced the microbial composition, while SOC and ammonium-N strongly influenced the microbial activity. In conclusion, manure substitution of inorganic fertilizer, especially at a higher substitution rate, was more efficient for improving soil quality and biological functions.

    Soil carbon stocks in Indonesian (agro) forest transitions: Compaction conceals lower carbon concentrations in standard accounting
    Hairiah, Kurniatun ; Noordwijk, Meine van; Sari, Rika Ratna ; Saputra, Danny Dwi ; Widianto, ; Suprayogo, Didik ; Kurniawan, Syahrul ; Prayogo, Cahyo ; Gusli, Sikstus - \ 2020
    Agriculture, Ecosystems and Environment 294 (2020). - ISSN 0167-8809
    Agroforestry - Bulk density - Carbon accounting - Carbon concentration - Climate change mitigation - IPCC - Soil carbon

    Soil changes matter for the global carbon (C) balance although belowground response to land use change is slower and less obvious than that aboveground. Impacts of changes from natural forest to a range of intermediate tree-based land uses (‘agroforestry’) and non-tree agriculture remain contested. Standard C-stock accounting for a fixed sampling depth depends on changes in both Corg concentrations and bulk density, often with opposite effects. Confounding factors that, beyond current vegetation, influence Corg (soil texture, minerology, drainage, elevation and soil pH) may also influence bulk density. Because land use may not be random with respect to inherent soil properties, differences in soil C-stock between land uses can have multiple causes. We compiled and analysed data from six landscapes in Indonesia (volcanic and other mineral soils; Sumatra, Kalimantan; Java, Sulawesi) where chronosequences of forest, various agroforestry systems and open-field agriculture had been sampled. Our data analysis (617 samples within 0−30 cm depth; 8 land use types) showed that a pedotransfer function for effects on Corg of texture, elevation and soil pH reduced the relative standard error of means per land use type, reduced the range (Max–Min)/Avg and led to a more consistent pattern in apparent land use effects. Relative to natural forest reductions in Corg concentration in the 0−30 cm layer (corrected for confounding factors) averaged 8–20 % in degraded forest, complex agroforest, oil palm plantations and older forest plantation plots, and 25–30 % in simple agroforestry, monoculture tree crops and woodlots, or over 40 % in non-tree (mostly cropped) plots. However, calculated C-stock change was small due to an observed increase (up to 30 %) of bulk density relative to that of natural forest. This implies that up to 23 % additional Corg became included in the soil sampling, resulting in a non-negligible bias (underestimate) in estimated soil carbon loss based on internationally agreed C-stock accounting.

    Standardised soil profile data to support global mapping and modelling (WoSIS snapshot 2019)
    Batjes, Niels H. ; Ribeiro, Eloi ; Oostrum, Ad Van - \ 2020
    Earth System Science Data 12 (2020)1. - ISSN 1866-3508 - p. 299 - 320.

    The World Soil Information Service (WoSIS) provides quality-assessed and standardised soil profile data to support digital soil mapping and environmental applications at broadscale levels. Since the release of the first "WoSIS snapshot", in July 2016, many new soil data were shared with us, registered in the ISRIC data repository and subsequently standardised in accordance with the licences specified by the data providers. Soil profile data managed inWoSIS were contributed by a wide range of data providers; therefore, special attention was paid to measures for soil data quality and the standardisation of soil property definitions, soil property values (and units of measurement) and soil analytical method descriptions. We presently consider the following soil chemical properties: organic carbon, total carbon, total carbonate equivalent, total nitrogen, phosphorus (extractable P, total P and P retention), soil pH, cation exchange capacity and electrical conductivity. We also consider the following physical properties: soil texture (sand, silt, and clay), bulk density, coarse fragments and water retention. Both of these sets of properties are grouped according to analytical procedures that are operationally comparable. Further, for each profile we provide the original soil classification (FAO, WRB, USDA), version and horizon designations, insofar as these have been specified in the source databases. Measures for geographical accuracy (i.e. location) of the point data, as well as a first approximation for the uncertainty associated with the operationally defined analytical methods, are presented for possible consideration in digital soil mapping and subsequent earth system modelling. The latest (dynamic) set of quality-assessed and standardised data, called "wosis-latest", is freely accessible via an OGC-compliant WFS (web feature service). For consistent referencing, we also provide time-specific static "snapshots". The present snapshot (September 2019) is comprised of 196 498 geo-referenced profiles originating from 173 countries. They represent over 832 000 soil layers (or horizons) and over 5.8 million records. The actual number of observations for each property varies (greatly) between profiles and with depth, generally depending on the objectives of the initial soil sampling programmes. In the coming years, we aim to fill gradually gaps in the geographic distribution and soil property data themselves, this subject to the sharing of a wider selection of soil profile data for so far under-represented areas and properties by our existing and prospective partners. Part of this work is foreseen in conjunction within the Global Soil Information System (GloSIS) being developed by the Global Soil Partnership (GSP). The "WoSIS snapshot-September 2019" is archived and freely accessible at https://doi.org/10.17027/isric-wdcsoils.20190901 (Batjes et al., 2019).

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