Use In Agro-ecosystems Research Articles

Effect of detrital subsidy on the Collembola community structure in winter wheat agroecosystems

Mulch is widely used for improving soil quality and maintaining crop productivity. The effects of mulch use in agroecosystems can be assessed by the state of the soil biota. Springtails (Collembola) are a representative group of soil animals in agroecosystems that survive well under agricultural field conditions. We assessed the effect of adding a detrital subsidy with different carbon to nitrogen ratio (C:N) on springtails in a 4-year series of field experiments in winter wheat agroecosystems located in two agroecological zones (broad-leaved forest and steppe). The mulch effect depended on weather conditions. In dry years, the addition of mulch led to an increase in the proportion of epedaphic (upper-litter dwellers) springtails in the broad-leaved forest zone and to an increase in the proportion of atmobiotic forms (mostly inhabiting macrophytes) in the steppe zone. These changes begin to manifest approximately 1.5 months after the detrital subsidy addition. In general, mulch application had a positive and stabilizing effect on the springtail community structure in winter wheat agroecosystems, regardless of the agroecological zone. Our study showed that the addition of detrital subsidy helps to increase the abundance and stabilize the diversity of the springtail community. Changes observed in the structure of the Collembola community can be an indicator of improved soil health, and springtails can be used in assessing the effectiveness of agricultural practices.

Mineralized nitrogen uptake by plants of the use of synthetic nitrogen fertilization in agriculture

The underground transfer of nitrogen from non-food crop residues to cash crops is an important tool to ensure decent crop yields and balance N use in agroecosystems. Laboratory experiments were performed to determine nitrogen migration in spring wheat at different growth stages using labelled nitrogen. In the first stage of the experiment, Artemisia dubia was grown in climate chambers (Climacell CLC-707-TV), with air temperature cycles of 8 h at 15 °C and 16 h at 20 °C, and fertiliz using 15N isotope enriched ammonia nitrate. In the second stage of the experiment, spring wheat was sown and grown to full maturity in two soils of differing soil acidity (pH 3.93 ± 0,04 and pH 7.07 ± 0,08) and mixed with the chopped pieces (3–5 cm mean length) of Artemisia dubia above-ground biomass obtained in the first stage of the experiment. Each soil had four experimental treatments: non-enriched biomass; non-enriched biomass and fertilizer (170 N kg h−1); biomass enriched by 15N and no fertilizer, and 15N enriched biomass and fertilizer (170 N kg h−1). Spring wheat and soil were sampled every two weeks for dry matter (DM), total N and 15N content measurements during the experiment (13 weeks). The results showed that improved crop nitrogen utilization from Artemisia dubia residues were achieved when additional crop fertilizers was not used. It implies that adding additional nitrogen might increase the degradation of plant biomass, but at the same time cause environmental pollution by leaching as plants use it slightly for their growth.

Evaluation of Iron Chlorin e6 disappearance and hydrolysis in soil and garlic using salting-out assisted liquid-liquid extraction coupled with high-performance liquid chromatography and ultraviolet-visible detection

Iron Chlorin e6 (ICE6), a star plant growth regulator (PGR) with independent intellectual property rights in China, has demonstrated its efficacy through numerous field experiments. We innovatively employed salting-out assisted liquid-liquid extraction (SALLE) with HPLC-UV/Vis to detect ICE6 residues in water, soil, garlic seeds, and sprouts. Using methanol and a C18 column with acetonitrile: 0.1% phosphoric acid mobile phase (55:45, v:v), we achieved a low LOQ of 0.43 to 0.77 μg kg−1. Calibration curves showed strong linearity (R2 > 0.992) within 0.01 to 5.00 mg kg−1. Inter-day and intra-day recoveries (0.05 to 0.50 mg kg−1) demonstrated high sensitivity and accuracy (recoveries: 75.36% to 107.86%; RSD: 1.03% to 8.78%). Additionally, density functional theory (DFT) analysis aligned UV/Vis spectra and indicated ICE6's first-order degradation (2.03 to 4.94 days) under various environmental conditions, mainly driven by abiotic degradation. This study enhances understanding of ICE6's environmental behavior, aids in risk assessment, and guides responsible use in agroecosystems.

Transitioning Wintering Shorebirds to Agroecosystem: A Thorough Evaluation of Habitat Selection and Conservation Concern

Habitat fragmentation and degradation in natural wetlands has resulted in declines in the populations of shorebirds in the Indian subcontinent. Shorebirds rely on these wetlands as wintering or stop-over sites along the southern extent of the Central Asian Flyway. Shorebirds are known to utilize agroecosystems as alternate foraging habitats. The suitability of agroecosystems as foraging areas for overwintering migratory shorebirds has not been well studied in the Indian subcontinent. We conducted a comprehensive assessment of published literature and compiled field observations to investigate the importance of inland and coastal agroecosystems for shorebirds in India. We assessed the shorebird populations at natural wetlands: mudflats and mangroves of Kadalundi Vallikkunnu Community Reserve (KVCR) and Puthuvypu sand beach, as well as adjacent agroecosystems on the west coast of India, including Sanketham Wetlands, Manthalakkadavu, Vazhakkad, Elamaram, Kodinhi, and Kooriyad. On the east coast, we assessed the natural wetland habitats of Valinokkam, Point Calimere, and Pichavaram and evaluated inland agroecosystems in regions, such as Jammu and Kashmir, Punjab, Rajasthan, Gujarat, Uttar Pradesh, Tamil Nadu, and Kerala. Fifty-three shorebird species utilize diverse agroecosystems from various parts of India. While studies on the use of agroecosystems by shorebirds are limited on the east coast, evidence suggests that major wintering sites are adjacent to paddy fields, fostering substantial shorebird diversity. In Pichavaram, Point Calimere, and Gulf of Mannar regions, 22 shorebird species utilize agroecosystems, including the notable near-threatened Eurasian Curlew. Seventeen of these species are winter arrivals, highlighting the crucial role agroecosystems play as stopover areas. On the west coast, 19 shorebird species appear to utilize agroecosystems in Kooriyad, Manthalakkadavu, Vazhakkad, Sanketham Wetlands, Elamaram, and Kodinhi. Few species use agricultural fields in the north (Jammu and Kashmir). Paddy fields, that are flooded as part of the cropping cycle, support diverse prey species, such as macroinvertebrates, amphibians, and small fish, that could attract and support migratory shorebirds. Agricultural practices like fallowing, flooding, and ploughing could further increase the abundance and accessibility of prey for shorebirds, drawing them in greater numbers. It is crucial to recognize that unsustainable and unethical agricultural methods could detrimentally affect shorebird numbers. The accumulation of pesticide residues and the contamination from heavy metals could also threaten shorebirds. As a result, there is an urgent need for detailed research to better evaluate the importance of agroecosystems in supporting resident or migratory shorebirds. Systematic studies that explain the population dynamics, habitat selection trends, habitat utilization, and the over-summering behavior of the migratory birds at agroecosystems are needed. Implementing sustainable conservation strategies and adopting environmentally friendly agricultural practices are essential to support the rich biodiversity of the region.

A comparison of moderate and high spatial resolution satellite data for modeling gross primary production and transpiration of native prairie, alfalfa, and winter wheat

Although agroecosystems have a significant potential to offset carbon dioxide (CO2), the amount of CO2 captured can vary significantly depending on management practices. Accurate estimation of gross primary production (GPP) and transpiration (T) of agroecosystems at the field scale are essential for the study of food security and water resource management. To date, the carbon and water fluxes data products for commercial agroecosystems are limited, mostly at the moderate spatial resolution (MSR, hundreds of meters), which cannot be used to assess the temporal dynamics of GPP and T at the field scale. This study used the vegetation photosynthesis model (VPM) and vegetation transpiration model (VTM) to estimate field-level daily GPP (GPPVPM) and T (TVTM), respectively, in native prairie, alfalfa (Medicago sativa L.), and winter wheat (Triticum aestivum L.) in central Oklahoma, USA. We evaluated the reliability and advantages of vegetation indices (enhanced vegetation index, EVI and land surface water index, LSWI) in monitoring the land surface phenology using moderate spatial resolution data from Moderate Resolution Imaging Spectroradiometer (MODIS) and high spatial resolution (HSR, tens of meters) data from Landsat and Sentinel-2. The accuracy of GPPVPM and TVTM estimates at different spatial scales was evaluated using GPP (GPPEC) and evapotranspiration (ETEC) from the eddy flux tower sites, respectively. Results demonstrate the capacity of VPM and VTM to estimate the field-level carbon and water flux dynamics and their responses to weather conditions. The use of HSR vegetation indices helped to address certain challenges faced by MSR indices, especially in capturing the crop phenology in smaller areas with conservation measures or disturbances. The findings highlight the importance of using HSR GPP estimates to reduce uncertainty in quantifying CO2 fluxes for croplands and grasslands. The findings also demonstrate the ability of the models to track field-level vegetation phenology, carbon uptake, and water use in agroecosystems under different management practices.

Nanobiochar Associated Ammonia Emission Mitigation and Toxicity to Soil Microbial Biomass and Corn Nutrient Uptake from Farmyard Manure.

The unique properties of NB, such as its nano-size effect and greater adsorption capacity, have the potential to mitigate ammonia (NH3) emission, but may also pose threats to soil life and their associated processes, which are not well understood. We studied the influence of different NB concentrations on NH3 emission, soil microbial biomass, nutrient mineralization, and corn nutrient uptake from farmyard manure (FM). Three different NB concentrations i.e., 12.5 (NB1), 25 (NB2), and 50% (NB3), alone and in a fertilizer mixture with FM, were applied to corn. NB1 alone increased microbial biomass in soil more than control, but other high NB concentrations did not influence these parameters. In fertilizer mixtures, NB2 and NB3 decreased NH3 emission by 25% and 38%, respectively, compared with FM alone. Additionally, NB3 significantly decreased microbial biomass carbon, N, and soil potassium by 34%, 36%, and 14%, respectively, compared with FM. This toxicity to soil parameters resulted in a 21% decrease in corn K uptake from FM. Hence, a high NB concentration causes toxicity to soil microbes, nutrient mineralization, and crop nutrient uptake from the FM. Therefore, this concentration-dependent toxicity of NB to soil microbes and their associated processes should be considered before endorsing NB use in agroecosystems.

Mortality, developmental biology and cellular immunity in Achroia grisella (Fabricius, 1794) (Lepidoptera: Pyralidae) larvae exposed to azadirachtin

Azadirachtin, obtained from neem trees, can be a robust alternative to synthetic pesticides for the control of agricultural pests with no resistance problems. Azadirachtin-induced influences on mortality, life history traits and cellular immunity indicators of the lesser wax moth Achroia grisella (Fabricius, 1794) (Lepidoptera: Pyralidae) were evaluated. The experiments were conducted under controlled laboratory conditions at Balıkesir University. The topical application of azadirachtin gave an LD50 of 0.02 mg/ml whereas the PD50 (deaths without pupation) was 0.05 mg/ml. The prolongation of the larval stage and adult emergence time was significantly increased at 0.05 mg/ml and 0.1 mg/ml while the duration of the pupal stage was only significant at 0.1 mg/ml. Adult emergence ratios and longevity were reduced at all doses. Topical application of azadirachtin caused a marked decrease in the number of circulating hemocyte counts and spreading ability 24 and 48 h after treatment, however, the variations in plasmatocyte and granulocyte counts were not significant. Although azadirachtin has potential effects in the control of A. grisella, its effects on biological control agents such as parasitoids and predators must be determined to recommend its safe use in agroecosystems.

Preharvest Environmental and Management Drivers of Multidrug Resistance in Major Bacterial Zoonotic Pathogens in Pastured Poultry Flocks.

Due to nutritional benefits and perceived humane ways of treating the animals, the demand for antibiotic-free pastured poultry chicken has continued to be steadily rise. Despite the non-usage of antibiotics in pastured poultry broiler production, antibiotic resistance (AR) is reported in zoonotic poultry pathogens. However, factors that drive multidrug resistance (MDR) in pastured poultry are not well understood. In this study, we used machine learning and deep learning approaches to predict farm management practices and physicochemical properties of feces and soil that drive MDR in zoonotic poultry pathogens. Antibiotic use in agroecosystems is known to contribute to resistance. Evaluation of the development of resistance in environments that are free of antibiotics such as the all-natural, antibiotic-free, pastured poultry production systems described here is critical to understand the background AR in the absence of any selection pressure, i.e., basal levels of resistance. We analyzed 1635 preharvest (feces and soil) samples collected from forty-two pastured poultry flocks and eleven farms in the Southeastern United States. CDC National Antimicrobial Resistance Monitoring System guidelines were used to determine antimicrobial/multidrug resistance profiles of Salmonella, Listeria, and Campylobacter. A combination of two traditional machine learning (RandomForest and XGBoost) and three deep learning (Multi-layer Perceptron, Generative Adversarial Network, and Auto-Encoder) approaches identified critical farm management practices and environmental variables that drive multidrug resistance in poultry pathogens in broiler production systems that represents background resistance. This study enumerates management practices that contribute to AR and makes recommendations to potentially mitigate multidrug resistance and the prevalence of Salmonella and Listeria in pastured poultry.

Life History of Chrysodeixis includens (Lepidoptera: Noctuidae) on Positively Charged Zein Nanoparticles.

Research indicates that nanoparticles can be an effective agricultural pest management tool, though unintended effects on the insect must be evaluated before their use in agroecosystems. Chrysodeixis includens (Walker) was used as a model to evaluate chronic parental and generational exposure to empty, positively charged zein nanoparticles ((+)ZNP) and methoxyfenozide-loaded zein nanoparticles (+)ZNP(MFZ) at low-lethal concentrations. To determine concentration limits, an acute toxic response test on meridic diet evaluated (+)ZNP(MFZ) and technical grade methoxyfenozide using two diet assay techniques. No differences in acute toxicity were observed between the two treatments within their respective bioassays. With these results, population dynamics following chronic exposure to low-lethal concentrations were evaluated. Parental lifetables evaluated cohorts of C. includens reared on diet treated with LC5 equivalents of (+)ZNP, (+)ZNP(MFZ), or technical grade methoxyfenozide. Compared to technical grade methoxyfenozide, (+)ZNP(MFZ) lowered both the net reproductive rate and intrinsic rate of increase, and was more deleterious to C. includens throughout its lifespan. This was contrasted to (+)ZNP, which showed no differences in population dynamics when compared with the control. To evaluate chronic exposure to (+)ZNP, generational lifetables reared cohorts of C. includens on LC5 equivalent values of (+)ZNP and then took the resulting offspring to be reared on either (+)ZNP or untreated diet. No differences in lifetable statistics were observed between the two treatments, suggesting that (+)ZNP at low ppm do not induce toxic generational effects. This study provides evidence into the effects of nanodelivered methoxyfenozide and the generational impact of (+)ZNP.

Litter decomposition by soil fauna: effect of land use in agroecosystems

Soil fauna plays a key role in organic matter decomposition. Litter decomposition depends on the relationships of soil fauna and microorganisms as well as climate and litter quality. The decomposer community is sensitive to land use. Thus, physical-chemical disturbances, like soil tillage, can exercise important control on the soil fauna. In order to study the effect of land use and its impact on litter decomposition by soil fauna, a litter-bag experiment was conducted in the Pampa Serrana region, Azul district, Argentina. Litter-bags were made in three different mesh-sizes, allowing the access of micro, micro + meso and micro + meso + macrofauna. Four different treatments were defined: naturalized grassland and three agricultural agroecosystems under different tillage systems, i.e., conservation tillage, conventional-conservation tillage and conventional tillage. Decomposition rate and remaining litter were measured across three different seasons. We found that naturalized grassland obtained the highest decomposition rates and the least remaining litter compared to conservation and conventional tillage systems. No difference in litter decomposition was identified among agricultural agroecosystems. Micro + meso + macrofauna presented the highest decomposition rate and the lowest remaining litter of soil fauna groups, in all agroecosystems. In contrast, microfauna decomposition rate was the lowest and produced the highest remaining litter. Micro + mesofauna presented values of decomposition rate and remaining litter that differed significantly from the rest of the groups in some seasons. These results highlight the importance of soil fauna in litter decomposition and the negative effects of different land use systems on litter decomposition by soil fauna.

Assessment of the Short-Term Fertilizer Potential of Mealworm Frass Using a Pot Experiment

The forecasted growth of insect production in the next few years will generate high quantities of frass (insect excreta). Although frass is increasingly considered a potential fertilizer, the dynamics of nutrient supply by frass is still poorly understood. Here, we aimed at gaining insight into the short-term fertilizer value of frass from mealworm (Tenebrio molitor L.) in order to optimize its sustainable use in agroecosystems. Using a short-term pot experiment, we showed that, even though frass has a great potential to be used as a substitute of mineral NPK fertilizer, its N fertilizer potential is mediated by its rate of application. At 10 t ha−1, due to its fast mineralization coupled with improvement in microbial activity (assessed using Biolog EcoPlate), frass was as effective as mineral fertilizer to supply N to plant. By contrast, at 5 t ha−1, the lower frass mineralization induced a reduced N uptake compared to its mineral control. Unlike N, frass was as effective as mineral fertilizer to supply P and K to plants irrespective of its application rate. This was attributed to the presence of P and K in a readily available form in frass. Taken together, our results indicate that mealworm frass supplies very rapidly N, P and K to plants but its effects on N dynamics should be better investigated to warrant its sustainable use as an alternative fertilizer for managing NPK nutrition in cropping systems.

Synergism between local‐ and landscape‐level pesticides reduces wild bee floral visitation in pollinator‐dependent crops

Abstract The hazard pesticides pose to pollinators are well‐understood from laboratory studies. However, the field‐level response of pollinators to pesticide use in agroecosystems is not well‐established, nor is it clear if synergisms between pesticides affect pollinator visitation to crops. Here, we evaluated if fungicide and insecticide use posed a hazard to wild and honeybees at 87 cucurbit—pumpkin, cucumber, watermelon—farms in the Midwestern United States. We also evaluated if synergisms between local‐ (i.e. focal cucurbit field) and landscape‐level (i.e. surrounding crops) pesticide use influence wild and honeybee visitation to crop flowers. We found that bees were exposed to pesticides above regulatory levels of concern and that synergisms between a few local insecticides and landscape‐level fungicides reduced wild bee visitation to cucurbit flowers. Honey and bumblebee visitation to crops was not strongly influenced by synergisms between pesticides used at the local and landscape level. Synthesis and applications. We found pesticides posed hazards to honey and wild bee species. However, pesticides were less likely to affect short‐term visitation rates of honeybees compared with wild bee species. Thus, there is a need for changes in pesticide use at large spatial scales to reduce reliance on honeybees and maximize wild bee visitation to pollinator‐dependent crops. We suggest that a multifaceted approach, involving collaborations between farmers, consumers and policymakers, will be fruitful to promote changes in pesticide use and wild bee pollinators.

Differential responses of anuran assemblages to land use in agroecosystems of central Argentina

Agriculture has been identified as one of the largest contributors to the current global biodiversity crisis. Amphibians are declining worldwide, and the loss of habitat and water contamination related to agricultural land uses have been suggested as the main drivers of this phenomenon. In central Argentina, the Pampean Region combines the highest rates of grassland replacement of South America, the lowest percentage of protected areas of the country, and the lack of studies exploring diversity patterns of native amphibians occurring in agroecosystems. To fill these gaps, we surveyed anuran (frogs and toads) assemblages from 342 breeding ponds located in three ecological units from central Argentina (Rolling, Flooding, and Inland Pampas) during three breeding seasons (2015–2018). We aimed to evaluate the importance of breeding habitat characteristics (ponds) and the surrounding landscape features as drivers of anuran diversity occurring in agricultural landscapes under the primary land uses of the region (cattle grazing and soybean cropping). We tested for the effects of breeding habitat characteristics and landscape features on anuran richness, abundance, and individual species occurrence, using GLMM models and information-theoretic procedures. Results indicated that species richness and total abundances were differently influenced by the habitat and landscape features across the ecological units. Overall, vegetation cover of the ponds and land use were the most important variables influencing richness and anuran abundance. The positive influence of pond vegetation cover on anuran assemblages was registered for all the ecological units, while different patterns emerged when we analyzed the effects of land use surrounding the ponds. Land use expressed as the percentage of soy crop surrounding the ponds negatively affected richness and abundance of anurans of the Flooding Pampas, but the inverse relation was found for assemblages occurring in the Inland Pampas. Moreover, multiple competing models suggested a positive correlation between anuran diversity and land-use heterogeneity, and pond density. The differential responses of anuran assemblages among the ecological units can be related to a combination of several factors encompassing regional soil characteristics (i.e., soil texture), land-use intensity as well as requirements of anuran species. We discussed the particularities of each ecological unit in order to recognize those conservation efforts that will favor anuran diversity in these altered landscapes and further contribute to achieving agricultural sustainability.

Raptor resource use in agroecosystems: cover crops and definitions of availability matter

Zagorski, M. E. and R. K. Swihart. 2021. Raptor resource use in agroecosystems: cover crops and definitions of availability matter. Avian Conservation and Ecology 16(1):1. https://doi.org/10.5751/ACE-01719-160101

SCIENTIFIC AND PRACTICAL ASPECTS OF RATIONAL USE OF AGRICULTURAL SCAPES OF THE MIDDLE TRANSPORT IN THE CONTEXT OF THE STRATEGY OF SUSTAINABLE DEVELOPMENT OF THE REGION

The necessity of studying the current condition of agro-landscapes of Middle Transnistria in the context of the strategy of sustainable development of rural territorial communities of the region has been analysed. After all, ecologically safe use of agroecosystems of any region should become one of the necessary conditions for ecologically balanced development of its agrosphere. The authors note that the current condition of agro-landscapes has been characterized by significant diversity and complex landscape-typological structure. The differences of agro-landscapes in economic use have been presented, which led to the allocation of such subclasses: field, meadow-pasture, garden. The authors used different approaches and methods to study the modern agricultural landscapes of Middle Transnistria. The most significant were general scientific and specific scientific approaches. Among them the following were used: traditional or classical (comparative, historical, genetic, evolutionary) and specific (constructive, socio-economic, systemic, ecological, landscape-typological, informational, sociological) research approaches. Among the research methods most used: systemic, genetic, cartographic, morphometric, predictive and comparative. It has been established that the economic use of different subclasses of agrolandscapes of the region depends on the climatic, hydrological, orographic, edaphic and landscape-ecological conditions of the region. The characteristics of garden landscapes have been determined, which are located mainly on steep slopes, leveled terraces of river valleys, territories of former field landscapes. Location on the appropriate types of areas, species composition of plantations and specific agronomic regime, determine the formation of these unique garden landscapes. Here certain favorable microclimatic conditions, plant and animal groups which are inherent in specific garden landscape complexes are created. Among them are unique palmette orchards and those within which there are rare and adapted to the natural conditions of the region varieties of fruit trees. The uniqueness of the garden landscapes of Middle Transnistria is considered on the example of a natural area near the village. Dmytrashkivka, Vinnytsia region, where valuable plots of palm gardens are located. A set of measures proposed to promote the rational use of agricultural landscapes of Middle Transnistria in the context of implementing strategies for sustainable development of the region

Ecosystem service mapping in soybean agroecosystems

Depending on the type and intensity of use of agroecosystems, they provide important goods and ecosystem services (ES) to human. This study assesses supporting, regulating, provisioning and cultural services in 48 Iranian soybean fields under conventional and conservation cropping systems. We hypothesize that the present agricultural soybean land use in Gorgan County is the reason for a reduced performance of ES. We updated the Millennium Ecosystem Assessment (MEA) framework for mapping of ES and included new indicators like insect biodiversity, biodiversity indexes according to Shannon-Wiener, Simpson, Inverse Simpson and Margalef, soil microbial respiration, and quantification of soil conservation by using the Universal Soil Loss Equation (USLE). To quantify carbon sequestration and microbial respiration, soil samples were taken at depths of 0–30 cm before cultivation start in late May 2017 and after soybean harvest in early October 2017. Oxygen production was estimated based on net primary production. Various types of supporting services were evaluated in two general groups, including insect communities and plant biodiversity. The results show that conservation cropping systems in general provide better performing ES than conventional cropping systems. Soil microbial respiration was significantly higher in conservation fields. The average oxygen production on conventional fields was 79.9 ton per ha, compared to 59.9 ton per ha in conservation fields. The biodiversity assessment showed that species richness and all diversity indexes in conservation fields were higher than conventional agroecosystems. From a soil conservation point of view, the rates of soil erosion according to USLE were estimated at an average of 996.64 and 417.63 kg per ha under conventional and conservation fields, respectively. In a spatial distinction, the eastern part of the county exposes the highest soil erosion. Regulating services for carbon sequestration were high in the southern region and on fields close to forest ecosystems. Provisioning services of soybean yield, oil and protein contents were highest in the western and central parts and lowest in the northern part of the study area. As the first report of ecosystem services mapping in conservation and conventional cropping systems in Iran, we confirm that conservation cropping systems in general provide better performing ES than conventional cropping systems.

Interactions between Elk (<i>Cervus canadensis</i>) and invasive Feral Swine (<i>Sus scrofa</i>) on the Canadian Prairies

Elk (Cervus canadensis), a native species on the Canadian Prairies, makes extensive use of agro-ecosystems. Feral Swine (Sus scrofa) is a highly invasive species introduced to western Canada in the late 1980s; it is now endemic and rapidly expanding its range across the Canadian Prairies. Here we consider a series of 14 trail camera photos obtained near St. Breiux, Saskatchewan on 18 November 2018. Taken at night over 67 minutes, they document close, non-aggressive encounters between Elk and Feral Swine. We believe that these are the first documented observations of close (<5 m) interactions between free-ranging Elk and Feral Swine in North America that include no indications of fear response or displacement of one species by the other. These types of indirect interactions among species have important implications in terms of potential risk of disease transmission and interpreting potential ecological impacts of invasive Feral Swine on native large mammals.

Potential for insecticide-mediated shift in ecological dominance between two competing aphid species

Competition is a key structuring component of biological communities, which is affected by both biotic and abiotic environmental stressors. Among the latter, anthropic stressors and particularly pesticides are noteworthy due to their intrinsic toxicity and large use in agroecosystems. However this issue has been scarcely documented so far. In this context, we carried out experiments under laboratory conditions to evaluate stress imposed by the neonicotinoid insecticide imidacloprid on intra and interspecific competition among two major wheat pest aphids. The bird cherry-oat aphid Rhopalosiphum padi L. and the English grain aphid Sitobion avenae F. were subjected to competition on wheat seedlings under varying density combinations of both species and subjected or not to imidacloprid exposure. Intraspecific competition does take place without insecticide exposure, but so does interspecific competition between both aphid species with R. padi prevailing over S. avenae. Imidacloprid interfered with both intra and interspecific competition suppressing the former and even the latter for up to 14 days, but not afterwards when a shift in dominance takes place favoring S. avenae over R. padi, in contrast with the interspecific competition without imidacloprid exposure. These findings hinted that insecticides are indeed able to mediate species interaction and competition influencing community structure and raising management concerns for favoring potential secondary pest outbreaks.

Physiological quality and dry mass production of Sorghum bicolor following silicon (Si) foliar application

The forthcoming of silicon (Si) highly soluble sources provided a suitable alternative to Si use in agroecosystems. There are many benefits associated to Si application in crops, such as improvement in feed quality. In this sense, the aim of this work was to evaluate the effect of Si foliar application on physiological quality, biomass production, and silicon accumulation in Sorghum bicolor. The experiment was conducted under greenhouse condition using an entirely randomized design, with five Si rates (0 as control), 0.84, 1.68, 2.52, and 3.36g L-1 of Si) applied as potassium and sodium silicate, with four repetitions. In each treatment, applied solutions were balanced in potassium in order to isolate the Si effect. The following measurements were taken: growth, biomass production, Si accumulation, and physiological quality. Supplying Si via leaves did not affect the sorghum growth rate and the relative chlorophyll index; however, leaf area increased 23% with the use of 2.36 g L-1 of Si. Physiological variables are influenced by increasing Si rates, with rates close to 1.68 g L-1 of Si causing the best photosynthetic rates and stomatal conductance. The use of potassium silicate as a source of silicon is an alternative for productivity increases up to 30%, but an economic study on the viability of its commercial application in the production chain of Sorghum bicolor is necessary.

Toxicity of iron oxide nanoparticles to grass litter decomposition in a sandy soil

We examined time-dependent effect of iron oxide nanoparticles (IONPs) at a rate of 2000 mg kg−1 soil on Cynodon dactylon litter (3 g kg−1) decomposition in an arid sandy soil. Overall, heterotrophic cultivable bacterial and fungal colonies, and microbial biomass carbon were significantly decreased in litter-amended soil by the application of nanoparticles after 90 and 180 days of incubation. Time dependent effect of nanoparticles was significant for microbial biomass in litter-amended soil where nanoparticles decreased this variable from 27% after 90 days to 49% after 180 days. IONPs decreased CO2 emission by 28 and 30% from litter-amended soil after 90 and 180 days, respectively. These observations indicated that time-dependent effect was not significant on grass-litter carbon mineralization efficiency. Alternatively, nanoparticles application significantly reduced mineral nitrogen content in litter-amended soil in both time intervals. Therefore, nitrogen mineralization efficiency was decreased to 60% after 180 days compared to that after 90 days in nanoparticles grass-litter amended soil. These effects can be explained by the presence of labile Fe in microbial biomass after 180 days in nanoparticles amendment. Hence, our results suggest that toxicity of IONPs to soil functioning should consider before recommending their use in agro-ecosystems.