Repellency Index Research Articles

Aphidicidal activity of nano-emulsions of spearmint oil and carvone against Rhopalosiphum maidis and Sitobion avenae

Different species of aphids, responsible for severe yield losses of cereal crops including wheat, (Triticum aestivum L.) are managed by insecticides, which are harmful to organisms and the environment under field conditions. Therefore, an environment friendly aphidicidal product of plant origin is required. Mentha spicata oil was found to be rich in carvone (81.88%), but the use of its oil and carvone in crop protection is lacking due to their volatility, poor solubility, and stability. A nanoformulaton not only solves these problems but also improve the efficacy and dose of the bioactive compounds. Thus, nano-emulsions of the oil and carvone prepared were characterized, and evaluated against Rhopalosiphum maidis (corn aphid) and Sitobion avenae (wheat aphid) The average droplet size of nano-emulsions of the oil and carvone was found to be 22.1 and 41.21 nm. Nano-emulsion of carvone exhibited higher aphid mortality (LC50 = 0.87–1.94 mg/mL) at 24 h and acetylcholinesterase inhibitory activity (IC50 = 0.07–3.83 mg/mL) compared to the nano-emulsion of the oil (LC50 = 2.87–2.81 mg/mL; IC50 = 1.66–5.34 mg/mL). The repellence index (RI) in nano-emulsion of essential oil was found to be higher (84.73 and 81.72%) at the highest concentration (0.05 µL/cm2) than that of carvone (77.59 and 80.98%) for R. maidis and S. avenae. Further, in silico studies also revealed the favourable binding energy (− 6.6 to − 8.5 kcal/mol) of the main compounds in the oil with acetylcholinesterase, facilitated by hydrophobic interactions and hydrogen bonding. This study suggests that the nano-emulsions of the essential oil and carvone can be explored under field conditions to establish efficacy for their utilization as aphidicidal and repellent products against aphids. In the present study, aphidicial and repellent activities of its essential oil and carvone were reported for the first time against R.maidis and S.avenae.

Soil water repellency under Eucalyptus stands of different age and its relationship with soil hydrological function and soil organic matter

Eucalyptus stands can modify soil hydrological functioning, by several mechanisms including the effect of the growing root system, changes in soil organic matter (SOM) and the occurrence of soil water repellency (SWR). This effect is expected to evolve with time, as tree root system develop and SOM is formed from tree litter. SWR can prevent water from entering the soil, reducing infiltration, while the effect of roots and SOM can improve structure, favoring infiltration. The aims of this study were: i- to determine the influence of Eucalyptus stands of different ages on soil physical and hydraulic properties and SWR phenomena; ii- to evaluate the effects of SOM content and composition on SWR; iii- to determine the relationship between SWR and soil physical properties; iv- to compare different methodologies for SWR evaluation. The soil studied was a in a silty loam Typic Argiudoll with Eucalyptus stands of 3, 7, 11 and 32 years. Samples were taken to determine saturated and near saturation hydraulic conductivity, water retention curve, total organic carbon and different fractions of SOM, and SWR. Different parameters were used to estimate SWR, including the repellency index (RI), water repellency cessation time (WRCT), modified repellency index (RIm), and a qualitative analysis of the shapes of cumulative infiltration curves. As main results, a reduction in total porosity (TP) in the first years of Eucalyptus plantation was found, followed by a steep increased in TP, mainly due to an increase in microporosity. Hydraulic conductivity decreased with stand age, which was attributed to a decrease in macro and mesoporosity and porosity connectivity. SOM and most SOM fractions were not affected by stand age. RI was a consistent method to estimate SWR in Eucalyptus stands, while WRCT and RIm determination was more difficult when non classical shapes of infiltration curves were obtained.

Repellent Effects of Coconut Fatty Acid Methyl Esters and Their Blends with Bioactive Volatiles on Winged Myzus persicae (Sulzer) Aphids (Hemiptera: Aphididae).

Myzus persicae (Sulzer) (Hemiptera: Aphididae) is one of the most important aphid crop pests, due to its direct damage and its ability to transmit viral diseases in crops. The objective is to test whether spraying nanoemulsions of botanical products repels winged individuals of M. persicae in a bioassay in culture chambers. The bioactive volatiles were applied on pepper plants at a dose of 0.2% alone or at 0.1% of each component in blends. A treated plant and a control plant were placed at each side of an entomological cage inside a growth chamber. The winged individuals were released between the plants, in a black-painted Petri dish suspended by wires in the upper half of the cage. The most repellent products were farnesol (repellency index, RI = 40.24%), (E)-anethole (RI = 30.85%) and coconut fatty acid methyl ester (coconut FAME) (RI = 28.93%), alone or in the following blends: farnesol + (E)-anethole + distilled lemon oil (RI = 36.55%) or (E)-anethole + distilled lemon oil + coconut FAME (RI = 30.63%). The observed effect of coconut FAME on aphids is the first report of this product having a repellent effect on a crop pest. Repellent substances for viral disease vectors should be further investigated to develop new strategies for plant protection.

Effects of soil heating changes on soil hydraulic properties in Central Chile

Wildfires are natural phenomena for most ecosystems on Earth. Many soil properties are impacted by fire, including soil hydraulic properties. We used a laboratory experiment to replicate the temperatures reached by a natural wildfire and documented the effects on soil hydraulic properties. This study hypothesizes that the impact of heating on soil hydrological properties can be explained by the interaction of a number of variables especially organic matter content (OM), cation exchange capacity (CEC), texture, pH, and electrical conductivity (EC). The main objective of this study is to explore the interconnections between soil hydraulic, chemical, and physical properties, focusing on understanding how these relationships change across different ecoregions and temperatures. Sixteen soils were collected across 16 sites susceptible to forest fires in the Central Zone of Chile and heated to 100 °C and 300 °C for two hours. These sites were representative of two distinct ecoregions: the Chilean Matorral (CM) and the Valdivian Temperate Forests (VTF). Chemical, physical, and hydraulic soil properties were measured before and after heating. At 100 °C, there were no significant changes in chemical, physical, or hydraulic soil properties. At 300 °C, significant changes were observed in most soil properties in soils from both ecoregions. The OM content and CEC decreased, whereas pH and electrical conductivity increased. In addition, clay content and water aggregate stability (WSA) decreased, while all hydraulic properties increased their values. The aforementioned results demonstrate that infiltration increased after the soil was heated. This can be attributed primarily to decreases in clay content. At the same time, the water repellency (R) index decreased, allowing water to more easily wet the soil particles. Correlations revealed that CEC and clay are the main factors ruling soil hydraulic properties at all temperatures. Clay mineralogy also contributes to the soil hydraulic behavior observed. Nonlinear models were developed to estimate hydraulic properties at 100 °C and 300 °C, using the main soil properties. The models illustrated that the soils of the CM ecoregion, which are characterized by lower OM and influence of clay/CEC ratio, would be less affected by fire compared to the soils of VTF. The water holding capacity would decrease in both ecoregions. However, due to the greater changes in OM and clay in VTF, the impact would be greater than in CM.11Ca2+ = Calcium cations (meq/ 100g); CEC = Cation exchange capacity (meq/ 100g); CM = Chilean Matorral; EC = Electrical conductivity (μS/cm); I = Cumulative infiltration (cm); K = Unsaturated hydraulic conductivity (mm/h); K+ = Potassium cations (meq/ 100g); Ks = Saturated hydraulic conductivity (mm/h); Mg2+ = Magnesium cations (meq/100g); Na+ = Sodium cations (meq/100g); OM = Organic matter (g/100g); R index = Water repellency index; Se = Ethanol sorptivity (cm/s05); Sw = Water sorptivity (cm/s05); VTF = Valdivian Temperate Forest; WSA = Water-stable aggregates (%).

Long-term field pH manipulation influence on microbial activity, water repellency and physical properties of soil

Abstract Studies across multiple soils find increasing pH decreases water repellency. In this study, water repellency and a range of other soil physical properties of bulk soils, aggregates and intact specimens were measured on a long-term pH field experiment on a single sandy loam soil under a ley-arable crop rotation, with soil pH adjustments occurring annually by adding FeSO4 or CaCO3, to lower or raise the pH, respectively. Crop impacts were investigated by comparing 3rd year grass-white clover to spring oats, at the beginning (May) and end (September) of the growing season to allow soil structure comparisons. As in previous research, increased CO2 microbial respiration (p<0.05) was found with increasing pH along the gradient, but in this study, we found only the aggregate and soil bulk density affected by soil pH. Soil-water contact angles differed between crops (p<0.05), as well as the repellency index of soil aggregates, however, there was no soil pH effect. Overall, differences in data were found to be a result of the various crops in the rotation rather than by soil pH, indicating only minor impacts on soil physical characteristics after > 55 years of chemical additions to amend soil pH.

Comparative analysis of essential oil efficacy against the Asian longhorned tick Haemaphysalis longicornis (Acari: Ixodidae).

This study evaluated the potential repellent and acaricidal effects of 4 essential oils (clove, eucalyptus, lavender, and mint) against the Asian longhorned tick Haemaphysalis longicornis, a vector of various tick-borne diseases in medical and veterinary contexts. Selected for their potential repellent and acaricidal properties, the 4 essential oils were tested on adult and nymph H. longicornis ticks at different concentrations. The experiment assessed mortality rates and repellency, particularly during tick attachment to host skin. There was a significant increase (p<0.05) in tick mortality and repellency scores across all groups. At a 1% concentration, adult tick mortality ranged from 36% to 86%, while nymph mortality ranged from 6% to 97%. Clove oil exhibited notable efficacy, demonstrating high mortality rates of nymphs and adults. Clove oil also displayed strong repellency properties, with a repellency index of 0.05, surpassing those of mint, eucalyptus, and lavender oils. Clove oil showed the highest effectiveness in deterring nonattached adult ticks (90%) and nymphs (95%) when applied to skin. Clove oil was the most effective against adult and nymph ticks, achieving mortality rates of 86% and 97%, respectively, and led to the highest nonattachment rates when applied to skin. In conclusion, essential oils such as clove, eucalyptus, lavender, and mint oils present promising results for tick population control.

Efficacy of Plant Extracts for the Control of Pepper Insect Pest (Green Peach Aphid (Myzus persicae L.)

Aphids pose significant threats to crop productivity, necessitating effective and sustainable pest management strategies. This study investigated the repellent properties of neem and papaya leaf extracts on green peach aphids and the impact of the extracts on plant growth in pepper (Capsicum spp.). The experiment involved 7 treatments and 3 treatment replications with varying concentrations of neem and papaya extracts (6.5 v:v, 7.5 v:v, and 8.5 v:v) compared to a control group (Distilled water). The Randomized Complete Block Design (RCBD) was used as an experimental design. The study site was Cuttington University’s College of Agriculture Research site. The distances between plots and blocks were 0.6 m and 1 m, correspondingly. In the laboratory bioassay, results uncovered distinct trends, with the control treatment exhibiting the highest mean aphid count (41.0), while neem 8.5 v:v (6.0) and papaya 8.5 v:v (8.1) treatments established substantial effectiveness in reducing aphid populations. The highest mean aphid counts following biopesticidal application were 48.0 and 76.7 after 1 and 2 weeks, respectively and were recorded in the untreated control plots, while the lowest mean aphid counts were 21.3 and 6.0 after 1 and 2 weeks, respectively. Furthermore, neem 8.5 v:v treatment consistently showed the highest mean values across plant height (16.2 cm), leaf length (8.2 cm), leaf width (5.2 cm), and repellency index (3.0), indicating potential positive impacts on plant growth and repellency. Untreated control measured the lowest values for plant height (13.8 cm), leaf length (6.0 cm) and repellency index (1.0). The study demonstrated the potential of both extracts to suppress aphid populations and enhance plant growth. Applying these natural extracts as part of an integrated pest management (IPM) strategy can be beneficial for controlling aphid infestations in pepper crops. Their use as repellents can reduce aphid populations, minimizing potential crop damage and yield losses.

Potential Repellency and Toxicity of Hexane Extracts from <i>Cyperus rotundus</i> to <i>Tetranychus urticae</i> Koch. (Acari: Tetranychidae)

The objective of this work was to evaluate the acaricidal and repellency effect of Cyperus rotundus extract, an important weed plant, on Tetranychus urticae adults. Randomized complete block with 4 replicates was adopted. The hexane C. rotundus extract was obtained from tubers using the Soxhlet apparatus, then diluted to 5 concentrations (C1-100%, C2-50%, C3-25%, C4-10% and C5-1%), and a control (distillate water). Results showed that five concentrations caused significant mortality of T. urticae adults 24, 48 and 72 hr after treatment. The higher mortality was observed with C1 concentration of C. rotundus extract 72 hr after treatment (97%). Three concentrations C1, C2 and C3 showed a repellent effect on T. urticae adults. The repellence index ranged from 25 to 55% for C3 and C1, respectively. The present study demonstrated that the C. rotundus extracts could be an effective acaricide on T. urticae adults since the LC50 obtained was 30.95%.

Exploring soil-root interactions: A comparative study of wheat species and soil types

Soil-plant interactions of different wheat species (e.g., common, synthetic, durum and wild emmer ancestor) have not been studied yet. Therefore, our study was conducted to examine the interactive effect of 39 treatments including four wheat species (twelve varieties) and three soil types (loamy sand, sandy loam and sandy clay loam) on soil physical and biophysical quality indicators in a greenhouse pot experiment. The rhizosphere data were compared with the no plant (control) soil as well. The results revealed that the rhizosphere soils had a greater soil organic carbon (SOC) storage compared to the no plant soil, with the synthetic wheat species possessing the highest SOC content (order of SOC: synthetic > durum > emmer > common > control). The highest and the lowest SOC values (0.79 and 0.69 kg 100 kg−1) were observed in the rhizosphere of synthetic wheat S88 and common wheat CK varieties, respectively. The SOC showed a positive correlation with root morphological traits such as root volume and root dry weight. Basal soil respiration (BSR) showed significant variation among the four wheat species, and common and emmer ones had the highest BSR values. The maximum and minimum values of BSR (21.9 and 10.9 mg CO2 kg−1 soil day−1) were observed in the rhizosphere of the common species planted in sandy loam soil and in the loamy sand bulk soil (control), respectively. The presence of plant roots significantly increased BSR compared to the control (bulk soil); on average, the BSR in the rhizosphere was 21% greater than the control. Both the wheat species and soil type significantly affected the soil water repellency index (RI) and wettability parameters, but the interactive effects of treatments (i.e., wheat species and soil type) were not significant. The soils in all of the studied treatments were sub-critically or slightly water repellent (i.e., contact angle lower than 90°). The RI values were measured in the order emmer > durum > common > control ≥ synthetic; however, the difference between the synthetic species and bulk soil was not significant. Plant roots increased the soil hydrophobicity by increasing the SOC storage and significant variations in RI among the wheat species indicated that the emmer, durum and common species with greater RI might have better soil physical quality in the rhizosphere. The wheat plants substantially increased water-stable aggregates and decreased water-dispersible clay in the rhizosphere compared to the bulk soil. These findings showed that wheat roots were able to alter the structural stability of the rhizosphere soil. Correlation analysis indicated that soil structural stability was closely related to the SOC, microbial activity, water repellency and root morphological traits. Principal component analysis was used to enhance visualization, identify interrelationships between soil quality indicators and categorize wheat varieties.

Hydraulic characterization of earthworm macropore surfaces using miniaturized infiltration data

Water repellency related to organic matter (OM) of coatings along the earthworm burrows (EB) walls can facilitate preferential flow due to limiting the water exchange with the soil matrix. The objectives of this work were (i) to characterize the hydraulic behavior of EB wall and the surrounding matrix using a miniaturized infiltrometer; (ii) to compare standard infiltration analyses with BEST-WR algorithm; and (iii) to determine the local spatial distribution of water repellency at the EB wall surface in relation to that of the OM composition. Infiltration experiments were carried out on intact sample surfaces, including the EB wall and the surrounding matrix. Soil samples were collected from Bt and C horizons in a characteristic Haplic Luvisol. Hydraulic conductivity (K) at different water pressure heads (h) and water and ethanol sorptivity (Sw and Se, respectively), water repellency index (RI) and water repellency cessation time (WRCT) were determined from infiltration data. The adapted Beerkan Estimation of Soil Transfer parameters (BEST) algorithm for water-repellent soils (BEST-WR) was used for analysing infiltration data. The potential water repellency index (PWRI), relating C-H with CO functional groups in OM, was determined at the same locations using diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. Lower values of K and Sw in the coatings as compared to the soil matrix were found related to higher PWI values. Water repellency was also reflected in the shape of the cumulative infiltration curves and in the RI-values. The latter were significantly higher for EB as compared to matrix surfaces. The fittings provided by the BEST-WR algorithm characterizing the hydraulic properties of the macropore surfaces were comparable to those obtained with standard method. The tested methods could help to improve the estimation of parameters for macropore-matrix mass exchange in two-domain models.

In Vivo Bioassay of the Repellent Activity of Caraway Essential Oil against Green Peach Aphid.

An in vivo dual choice bioassay with white cabbage as a host plant was used to determine the repellent effect of three different accessions of caraway (Carum carvi L.) essential oils (EOs) against the green peach aphid Myzus persicae (Sulzer). The dominant components of the EO were D-Carvone (47.3-74.4%) and D-limonene (25.2-51.9%), which accounted for 99.2-99.5% of the EOs determined by GC/MS. The EO with the highest D-limonene content (51.9%) showed the highest repellence (Repellency Index (RI) = +41%), which was stable up to 330 min. The incorporation of several surfactants with different hydrophilic-lipophilic balance values (from 12.4 to 16.7) with caraway EO caused a general inhibition of the repellent effect during the testing period (RI from +41% to -19%). Overall, the findings indicate that caraway EO could be used as a green peach aphid repellent, but more work is needed to formulate the EO into a ready-to-use product.

Ground Fire Legacy Effects on Water-Dynamics of Volcanic Tropical Soils

The forest floor is a critical component in maintaining the life cycles of forest ecosystems. It normally includes organic soil horizons, known as duff and litter, which are prone to be rapidly consumed after flaming and smoldering fires. This work aims to understand the legacy effects of surface and ground fires on the infiltration capacity of a volcanic forest soil. We studied five sites with fires recorded in the last 20 years. All of them are located in pine-oak forests of the volcanic mountain region in central Mexico with a temperate climate and Andic soil properties. Tension-infiltration tests were carried out to determine hydraulic conductivity and the number of active macropores. After each test, cores were taken to evaluate in a laboratory setting, where soil water repellency at different moisture concentrations and the integrative dynamic repellency index were determined. Field-saturated hydraulic conductivity was moderately high in all sites, with mean values of 13 and 42 mm·h−1 for burned and control plots, respectively. A non-linear relationship was found between recurrence and type of fires with the concentration of active pores and several dynamic water repellency parameters. This work confirmed the presence of latent combustion in these temperate neotropical forests. The changes in soil water repellency and hydraulic conductivity detected do not necessarily imply an exceeded soil infiltration capacity. However, many of the fires in this region are associated with increasing agricultural activities, so further studies are needed to determine if higher fire frequencies could exceed the resilience capacity of the soils triggering land degradation.

Biochar, manure and superabsorbent improve the physical quality of saline‐sodic soil under greenhouse conditions

AbstractThe increasing salinization and sodification of soils in drylands and irrigated systems present a great challenge to agricultural production and threaten soil quality. There is an urgent need to investigate potential strategies to remediate soils that are threatened by these processes. To address this challenge, the current study investigated the effects of organic and inorganic amendments and leaching fraction (LF) on physical and hydraulic properties including the soil water characteristic curve (SWCC), Dexter's index of soil physical quality (SDexter), bulk density (BD), saturated hydraulic conductivity (Ks), and water repellency index (RI) in a saline‐sodic soil. A greenhouse experiment was carried out in a completely randomized design with two factors (amendment and LF). The amendments included superabsorbent (1%) (SA), zeolite modified with CaCl2 (2%) (ZC), biochar (2%) (B), biochar + manure (2%) (BM), and a control (no amendment) (CT), and combined with two levels of LF (15% and 30%). Spring wheat (Triticum aestivum, ‘UG99’) was planted in the soil columns. After harvest, undisturbed samples were collected from each column for the determination of soil properties. The results demonstrated the effectiveness of the SA and organic amendments to enhance Ks and decrease BD. There was a significant (p < 0.01) positive effect of the amendments, particularly biochar and superabsorbent on the soil pore size distribution. The SA amendment significantly increased soil water retention, especially at high matric potentials (i.e., 0 to −80 hPa). The effect of organic amendments on the SWCC was in between those of the ZC and SA amendments. The SA and BM treatments were sub‐critically water repellent, while the ZC treatment increased soil water repellency. The SA, B, and BM15 treatments exhibited very good physical quality (SDexter > 0.05). The relative air and moisture capacities were optimal in the B‐amended soil at field capacity (matric potential –330 hPa). We conclude that B, BM, and SA are suitable amendments for reducing the adverse effects of salinity and sodicity via an improvement in soil physical quality.

Repelência de Ceratitis capitata (DIPTERA: TEPHRITIDAE) a biofertilizantes e extratos vegetais

Ceratitis capitata is considered the key pest of fruit production worldwide, due to its wide host variety. As an alternative control method for this pest, the objective of this research was to evaluate the repellency of C. capitata to liquid biofertilizers added to plant extracts. The repellency was evaluated through olfactory arenas, using the biofertilizer Vairo and the plant enrichment, diluted in distilled water at 10% and added in equal parts with plant extracts of neem, pitanga and rue at concentrations of 30, 40 and 50% p/v. The larval infestation index was evaluated from the fruits used in the repellency bioassay. The addition of plant biofertilizer and neem extract at 30% w/v showed the highest repellency index for C. capitata, resulting in only 1.6% of visiting flies. The lowest rate of larval infestation was observed in the Vairo biofertilizer + rue extract and in the plant biofertilizer + neem at concentrations of 30 and 40% w/v, with averages of less than one larva/fruit. Vairo biofertilizer + neem extract and plant biofertilizer + pitanga reduces the number of adult insects in fruits and Vairo biofertilizer + rue extract and plant biofertilizer + neem reduces the number of C. capitata larvae in treated fruits. The addition of biofertilizers to the plant extracts analyzed influences the repellency and larval incidence of C. capitata when the fruits are treated with these mixtures.

Factors governing soil hydrological function under long‐term tillage practices: Insight into soil water repellency

AbstractDrought is increasingly common due to frequent occurrences of extreme weather events, which further increases soil water repellency (SWR). It could reinforce the effect of SWR on soil functions under conservation tillage systems. However, the relationship between SWR and soil hydrological function is still unclear. We studied the impacts of SWR and soil structure on soil hydrological function. Three treatments were conducted in a long‐term tillage experiment: conventional tillage (CT), reduced tillage (RT), and no‐tillage (NT). Tillage, soil depth, and growth period had significant influences on SWR, soil structure (i.e., penetration resistance [PR], total porosity [TP], and mean weight diameter [MWD]), and soil hydrological functions (i.e., water storage, least limiting water range [LLWR], and plant available water). Compared to CT, NT and RT increased the water repellency index (RI) in 0–20 cm by 13.8%–40.1% and 6.5%–18.2% during the growth period. RI played a prominent role in increasing soil water storage compared to soil TP, PR, MWD, and SOC. PR was the most critical influence on LLWR compared to other variables. A structural equation model revealed that SWR directly affected soil hydrological function, whereas the effect of SWR (0.24) was smaller than that of soil structure (0.67). In addition, soil structure had a direct influence on SWR, indicating that the effect of SWR could be regulated by soil structure. Overall, this study showed a link between SWR and soil hydrological function and provides deeper fundamental insights into the role of SWR on the sustainability of conservation tillage.

Impact of duration of land abandonment on soil properties

Abstract Abandonment of agricultural fields triggers the ecosystem recovery in the process referred to as secondary succession. The objective of this study was to find the impact of secondary succession during 12 years lasting abandonment of agricultural fields with loamy sand and sandy loam soils on soil properties, namely soil organic carbon content, pH, water and ethanol sorptivity, hydraulic conductivity, water drop penetration time (WDPT), and repellency index (RI). The method of space-for-time substitution was used so that the fields abandoned at different times were treated as a homogeneous chronosequence. The studied soils showed a permanent increase in WDPT and a monotonous decrease in pH and water sorptivity with the duration of field abandonment. The dependence of the other characteristics on the duration of field abandonment was not unambiguous. The ethanol sorptivity decreased between 0 and 8 years of field abandonment, and increased between 8 and 12 years, when it copied a similar course of sand content during abandonment. The hydraulic conductivity halved within the first eight years of field abandonment and then increased statistically insignificantly between 8 and 12 years of abandonment. The repellency index decreased statistically insignificantly between 0 and 8 years of abandonment and then increased between 8 and 12 years.

Rapid artificial biocrust development by cyanobacterial inoculation and clay amendment

AbstractThe establishment of biological soil crusts is widely perceived as a main strategy to improve the ecological environment in arid and semi‐arid regions. However, artificial biocrusts fail to withstand environmental stresses when using traditional methods for initial establishment. Hence, in this study, kaolin, a common clay mineral, was introduced as a biocrust stabilizer by mixing at different mass ratios with Microcoleus steenstrupii for sand inoculation. The results showed that the addition of kaolin exhibited a significantly positive effect on promoting biocrust formation and accelerating biocrust development. Moreover, the artificial biocrust from 1:500 (algae: kaolin) inoculant achieved the best performance with coverage of 98%, and top layer thickness of 5.62 mm after 86 days of incubation. The highest contents of chlorophyll a, exopolysaccharides, and soluble protein were also observed in 1:500 mass ratio of algae: kaolin throughout the biocrust development process. As for the water retention performance, the results of contact angle, water drop penetration time (WDPT), and repellency index (RI) illustrated that biocrust improved water utilization in kaolin‐treated groups by delaying the time of water infiltration, especially in 1:500 group. After 86 days post inoculation, a series of common bacteria appeared in the biocrusts such as actinobacteria and acidobacteria, and decomposed metabolites from cyanobacteria as an energy source. This study gains new insights into clay minerals on biocrust development and puts forward a new approach for rapid artificial biocrust establishment to reverse desertification.

Influence of contamination with diesel oil on water sorptivity and hydrophobicity of sandy loam soil

AbstractThis paper shows the changes in water sorptivity (Sw) and hydrophobicity following soil contamination with petroleum hydrocarbons (PHs) under different soil moistures. Laboratory experiments were carried out to verify that contamination with PHs reduces Sw, thus affecting the infiltrability, which in practice influences the field water capacity and the availability of water for plants. Soil water repellency (SWR) was estimated by the repellency index (R) and water drop penetration time (WDPT). The increase in PHs contamination contributed to SWR and caused a significant decrease in Sw. With the decrease in moisture, the water sorptivity of the soil increased, reaching its maximum at 0.12–0.15 cm3 cm−3, which was the threshold value in the case of the analysed soil, and then decreased drastically. The R index and the WDPT revealed a similar trend, inversely related to the level of soil contamination with PHs. The increase in SWR and the accompanying decrease in Sw made the soil less resistant to drought. The total amount of water available to plants in the control soil was 19.04%, whereas contamination with PHs equal to 100 g kg−1 caused a decrease to 6.36%. The almost threefold decrease in the total amount of water has a fundamental influence on increasing the risk of soil drought. The results obtained indicated that the interrelationship presented between the level of contamination with PHs, water sorptivity, SWR and soil moisture are the keys to predicting the environmental effects of contamination with PHs. The obtained results indicate that the undertaken remediation measures aimed at restoring the hydrological function of the soil system should be preceded by an assessment of soil hydrophobicity.

Extractos Vegetales para el Manejo del Gorgojo del Frijol1

The bean weevil, Acanthoscelides obtectus (Say, 1831), is a problem for producers and storage of legumes. It is estimated to cause as much as 20% loss of production. It also reduces the quality of harvest and affects viability of seeds for sowing. Ethanol extracts from eight plants were evaluated: saltmarsh leaf, Baccharis glutinosa Pers.; eucalyptus, Eucalyptus globulus Labill; creosote bush, Larrea tridentata (Sessé & Moc. ex DC.) Cov.; tree tobacco, Nicotiana glauca Graham; cacachila, Karwinskia humboldtiana (Shult.) Zucc.; chinaberry seed, Melia azedarach L.; castor, Ricinus communis L.; and copalquin bark, Hintonia latiflora Bullock, at doses of 5, 10, 15, and 20% w/v. Corrected mortality and pest emergence, repellency index, percentage of damaged seed, and loss of germination capacity were evaluated. Results indicated that N. glauca and K. humboldtiana (10% w/v) were the best treatments with 0% damaged seed, no emergence of the F1 generation of the pest, and maintained ability to germinate. Extracts of the two plants might be an alternative to manage A. obtectus in stored beans.

Repellent, antifeedant and toxic effects of plants-extracts against Spodoptera frugiperda larvae (fall armyworm)

The fall armyworm (FAW), Spodoptera frugiperda, is a polyphagous pest because of the damage it causes to crops. The utilization of plant extracts with bioactive compounds for controlling S. frugiperda has been emerging to be a new venture. Therefore, this study aimed at analyse the impact of Adathoda vassica, Dathura metel, and Tagetes erecta extracts against FAW. Leaves were washed, air dried (27 ± 2○C) and powdered and their extracts were obtained with ethyl acetate as a solvent. Bio efficacy of extracts was studied through different concentrations (0.2, 0.4, 0.6 μg/μL) against third instar larvae of S. frugiperda to assess the contact toxicity, antifeedant activity and repellency effect. The presence of phytochemicals i.e; tannins, terpenoids, phenols, saponins, flavonoids and alkaloids were determined and characterized using FTIR analysis. The T. erecta was more effective against FAW larvae that caused significantly very high (P < 0.05) antifeedant activity, and contact toxicity with the lowest LD50 (at all concentrations). The degree of repellency was greatly influenced by the concentration of the extract. Low Index of Repellency (IR), high Percent Repellency (PR) and residual PR were observed in T.erecta and D.metel and the highest significant value (P < 0.05) was observed in T.erecta. Therefore, T.erecta can be categorized into the highest repellency class (Class V). The phytochemical and FTIR analysis confirmed the presence of bioactive compounds having the potential against S. frugiperda. Therefore, D.metel and T. erecta are showing the potentiality for pesticidal development.