Use In Agricultural Systems Research Articles

Enhancing sustainable crop production through integrated nutrient management: a focus on vermicompost, bio-enriched rock phosphate, and inorganic fertilisers – a systematic review

Securing a consistent food supply remains a pressing global challenge, particularly for small-scale farmers grappling with obstacles in enhancing agricultural yields, especially in tropical soils. Integrated Nutrient Management (INM) techniques, employing organic manures like vermicompost and bio-enriched rock phosphate, emerge as recommended solutions. Vermicompost is lauded for its nutrient richness and positive soil health impacts. At the same time, bio-enriched rock phosphate serves as a sustainable alternative to conventional phosphorus fertilisers, specifically tailored for tropical soil conditions. Despite individual studies assessing the effects of vermicompost, bio-enriched rock phosphate, and soluble fertilisers on plant growth, a comprehensive overview of their combined application is noticeably lacking. To fill this gap, this study employs the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) method to explore the synergies of combining these elements and their impacts on crop production and the environment. This review is among the first to comprehensively summarize the complexities of combining vermicompost, bio-enriched rock phosphate, and chemical fertilisers on various crops. It thoroughly examines potential advantages, disadvantages, effects on agricultural systems, socio-economic implications, and existing policies governing their usage. Our findings reveal that the combined application of vermicompost, bio-enriched rock phosphate, and soluble fertilisers leads to significant improvements in plant growth, yield, and soil properties. The optimal impact is observed when vermicompost constitutes 25% and soluble fertiliser comprises 75 or 100% of the recommended fertiliser dosage. Moreover, incorporating a mixture of phosphate-solubilizing bacteria (PSB) strains in rock phosphate further enhances its positive effects. Despite these positive findings, we identified gaps in comprehensive approaches addressing socio-cultural dimensions and the lack of literature on prevailing policies regarding vermicompost use in agricultural systems highlighting the need for a more holistic understanding of vermicompost incorporation and a better grasp of the institutional frameworks guiding these practices. However, to secure sustainable crop production, farmers need to integrate vermicompost and biofertilisers with chemical fertilisers. In fostering the adoption of sustainable and inclusive agricultural practices on small rural properties, it is advisable to incorporate agricultural education into farmer training programs.

Influence of Biochar Addition to Nursery Container Media: Trace Gas Efflux, Growth, and Leachate N

Abstract Biochar is a pyrolytic product generated by heating biomass in the absence of oxygen such as during bioenergy production. Biochar can be made from various feedstocks and research into its potential use in agricultural systems has examined its effects on plant growth, trace gas emissions, and N loss. However, since a paucity of work has examined biochar use in horticultural container production systems, we investigated how biochar additions to growth media impacted trace gas efflux (CO2, CH4, and N2O), plant growth, and N loss via leachate in two separate experiments: a peat-based greenhouse study using viola (Viola cornuta L. ‘Sorbet® XP Deep Orange’) and a pinebark-based outdoor study using daylily (Hemerocallis x ‘EveryDaylily Cream PBR’ L.). Biochar had little effect on viola growth, but growth inhibition was noted for daylily. Both studies clearly showed that N in leachate was reduced by biochar additions, with higher biochar rates having greater effects on reducing N loss. Reductions in N loss with biochar suggest improved N use efficiencies in agricultural systems. Biochar use also decreased N2O and CO2 fluxes in daylily, which suggests that biochar could help mitigate global climate change. Our results suggest that future studies should focus on testing lower rates of biochar in terms of growth and environmental impacts. The complexities of N management highlight the importance of developing biochar practices that increase N retention for the benefit of both agriculture and the environment. Species used in this study: viola (Viola cornuta L. ‘Sorbet® XP Deep Orange’); daylily (Hemerocallis x ‘EveryDaylily Cream PBR’ L.).

Sustainable Use of Organic Seaweed Fertilizer Improves the Metagenomic Function of Microbial Communities in the Soil of Rice Plants

The frequent use of chemical fertilizers in agricultural practices has developed into a serious environmental concern which urgently needs a solution to restrain their use in agricultural systems. Hence, there is an urgent need to investigate potential organic fertilizers from various natural resources to decrease the use of chemical fertilizers. Seaweed is among the natural resources with potential sustainability value. Our previous work has shown the effectiveness of seaweed fertilizer for increasing plant growth and soil beneficial microbiota. This study aims to evaluate the functional genes present in the soil of rice plants treated with seaweed fertilization. It involves amendments with reduced concentrations of chemical fertilizer in three groups: CF (only chemical fertilizer), CFSF1 (50% dose of CF + seaweed fertilizer 1 ton/ha), and CFSF2 (50% dose of CF + seaweed fertilizer 2 ton/ha). The rice plants supplemented with CFSF1 and CFSF2 were taller and faster to mature compared to CF. In addition, the primary macronutrients nitrogen (N), phosphorus (P), and potassium (K) were also significantly higher in soil supplemented with SF. Our findings showed increased ammonia-oxidizing archaea Crenarchaeota abundance in increasing SF treatments. The PICRUSt analyses indicated enriched functional genes and proteins in relation to amino acid, nucleotide, protein, and carbohydrate metabolism based on the KEGG, BioCyc, and PFAM databases. The current outcomes enhanced our understanding regarding the importance of microbial community for soil quality. Furthermore, seaweed supplementation has shown improvement in soil fertility, which significantly increases rice plant growth and productivity.

New frontiers of soil fungal microbiome and its application for biotechnology in agriculture.

The fungi-based technology provided encouraging scenarios in the transition from a conventionally based economic system to the potential security of sources closely associated with the agricultural sphere such as the agriculture. In recent years, the intensification of fungi-based processes has generated significant gains, additionally to the production of materials with significant benefits and strong environmental importance. Furthermore, the growing concern for human health, especially in the agriculture scenario, has fostered the investigation of organisms with high biological and beneficial potential for use in agricultural systems. Accordingly, this study offered a comprehensive review of the diversity of the soil fungal microbiome and its main applications in a biotechnological approach aimed at agriculture and food chain-related areas. Moreover, the spectrum of opportunities and the extensive optimization platform for obtaining fungi compounds and metabolites are discussed. Finally, future perspectives regarding the insurgency of innovations and challenges on the broad rise of visionary solutions applied to the biotechnology context are provided.

Cover crop termination timings and methods effect on cotton (Gossypium hirsutum L.) development and yield

AbstractCover crops have been promoted for use in agricultural systems due to both environmental and economic opportunities. Cotton (Gossypium hirsutum L.) growers in West Tennessee faced challenges in 2015 and 2016 with cover crop termination management which resulted in failed cotton stands. The objective of this experiment was to determine effects of cover crop termination timing and method on cotton emergence, development, and yield. Field experiments were conducted from 2018 to 2020 in both small plot and on‐farm scenarios across West Tennessee. Cover crop termination timings consisted of an at‐planting termination, 3 weeks prior to planting, and both a broadcast and furrow‐strip termination 6 weeks prior to planting. The cover crop termination methods consisted of chemical termination, mechanical termination, and chemical + mechanical termination. At‐planting termination reduced emergence by 25% and delayed maturity of 65% of the stand relative to a 6‐week broadcast termination. Mechanical termination reduced emergence by 26% and delayed maturity of 26% of the stand relative to the chemical and chemical plus mechanical termination treatments. Thrips injury ratings were greater in cotton following a chemical + mechanical termination of the cover crop. Damage from three‐cornered alfalfa hoppers (Sissistilus festinus) was less prevalent in cotton following cover crops terminated 6 weeks prior to planting in a broadcast method compared to other timings. While early season effects were observed, end‐of‐season yield differences were not noted. Still, producers in short season environments should be aware of the higher level of risk associated with at‐planting terminations or terminations.

Suitability of Fast-Growing Tree Species (Salix spp., Populus spp., Alnus spp.) for the Establishment of Economic Agroforestry Zones for Biomass Energy in the Baltic Sea Region

The main goal of this review was to provide an assessment of the potential of fast-growing tree species for the suitable transformation of agroforestry areas for biomass production in the Baltic Sea region. Our interest was to highlight the research on the management process of agroforestry zones by establishing short rotation plantations with the tree species Salix spp., Populus spp. and Alnus spp. to explore the prospects of planning these zones as biomass producers. Short rotation forestry (SRF) with trees whose rotation period is 15 to 30 years, depending on the species, is the most suitable approach for management of these agroforestry zones. Willows (Salix spp.) and poplars (Populus spp.) are suitable for short rotation coppice (SRC), as these tree species can be harvested at much shorter intervals, respectively, 1–5 and 4–10 years, facilitating their use in agricultural systems. The rotation period of Alnus spp. in short rotation plantations for energy wood production is generally assessed to be 15–30 years. The black alder plantations in agroforestry zones are used for sawnwood and firewood production, with a rotation period of 20–40 years. The calculated repayment period of the economic agroforestry zone is about 10–15 years, if 2021 costs and prices are used.

Evaluation of Allelopathic Potential of Pluchea indica on Brassica chinensis and Zea mays

Weeds have become one of the leading causes of crop production losses, including the cost of weed management, weed crop competition, and weed intervention with crop management practices. Moreover, herbicide use in agricultural systems is currently being debated due to the potential adverse effects on the environment and human health. The utilization of the allelopathic phenomenon is widely considered an alternative weed management strategy. However, allelopathic study of Pluchea indica plant was limited. P. indica is a flowering plant under family Asteraceae, locally known as Beluntas. Thus, this study was conducted to determine the allelopathic effects of the aqueous leaf extract of P. indica on the seedling growth of tested plant species and to investigate the effect of P. indica leaf debris on the growth of tested plant species. In this study, the allelopathic potential of P. indica leaves were investigated through petri dish bioassay and soil bioassay method. The two tested plant species were chosen for the bioassay: monocotyledonous; maize (Zea mays) and dicotyledonous; mustard (Brassica chinensis). These tested plant species were chosen for the experiment due to their known quick seedling growth behaviours and commonly used in allelopathic studies. The result showed that as the concentration of aqueous leaf extract increased, the inhibition percentage of the radicle length of B. chinensis and Z. mays were increased. However, stimulatory effect was observed on the radicle length of B. chinensis and Z. mays when 1.3%and 2.5% w/w P. indica leaf debris were applied. Thus, aqueous leaf extract and leaf debris of P. indica have potential allelopathic effects on the growth of B. chinensis and Z. mays. Further studies need to be conducted on other bioassay species especially weed species, to elucidate the allelopathic potential of P. indica in weed control.

Greenhouse gas emissions from global production and use of nitrogen synthetic fertilisers in agriculture

The global agri-food system relies on synthetic nitrogen (N) fertilisation to increase crop yields, yet the use of synthetic N fertiliser is unsustainable. In this study we estimate global greenhouse (GHG) emissions due to synthetic N fertiliser manufacture, transportation, and field use in agricultural systems. By developing the largest field-level dataset available on N2O soil emissions we estimate national, regional and global N2O direct emission factors (EFs), while we retrieve from the literature the EFs for indirect N2O soil emissions, and for N fertiliser manufacturing and transportation. We find that the synthetic N fertiliser supply chain was responsible for estimated emissions of 1.13 GtCO2e in 2018, representing 10.6% of agricultural emissions and 2.1% of global GHG emissions. Synthetic N fertiliser production accounted for 38.8% of total synthetic N fertiliser-associated emissions, while field emissions accounted for 58.6% and transportation accounted for the remaining 2.6%. The top four emitters together, China, India, USA and EU28 accounted for 62% of the total. Historical trends reveal the great disparity in total and per capita N use in regional food production. Reducing overall production and use of synthetic N fertilisers offers large mitigation potential and in many cases realisable potential to reduce emissions.

Progress and Applications of Plant Growth-Promoting Bacteria in Salt Tolerance of Crops.

Saline soils are a major challenge in agriculture, and salinization is increasing worldwide due to climate change and destructive agricultural practices. Excessive amounts of salt in soils cause imbalances in ion distribution, physiological dehydration, and oxidative stress in plants. Breeding and genetic engineering methods to improve plant salt tolerance and the better use of saline soils are being explored; however, these approaches can take decades to accomplish. A shorter-term approach to improve plant salt tolerance is to be inoculated with bacteria with high salt tolerance or adjusting the balance of bacteria in the rhizosphere, including endosymbiotic bacteria (living in roots or forming a symbiont) and exosymbiotic bacteria (living on roots). Rhizosphere bacteria promote plant growth and alleviate salt stress by providing minerals (such as nitrogen, phosphate, and potassium) and hormones (including auxin, cytokinin, and abscisic acid) or by reducing ethylene production. Plant growth-promoting rhizosphere bacteria are a promising tool to restore agricultural lands and improve plant growth in saline soils. In this review, we summarize the mechanisms of plant growth-promoting bacteria under salt stress and their applications for improving plant salt tolerance to provide a theoretical basis for further use in agricultural systems.

Exploring Trade-Offs Between Profit, Yield, and the Environmental Footprint of Potential Nitrogen Fertilizer Regulations in the US Midwest.

Multiple strategies are available that could reduce nitrogen (N) fertilizer use in agricultural systems, ranging from voluntary adoption of new N management practices by farmers to government regulations. However, these strategies have different economic and political costs, and their relative effectiveness in decreasing N leaching has not been evaluated at scale, particularly concerning potential trade-offs in crop yield and profitability. To inform policy efforts in the US Midwest, we quantified the effects of four policy scenarios designed to reduce fertilizer N inputs without sacrificing maize yields below 95%. A simulated dataset for economically optimum N rates and corresponding leaching losses was developed using a process-based crop model across 4,030 fields over 30 years. Policy scenarios were (1) higher N prices, (2) N leaching fee, (3) N balance fee, and (4) voluntary reduction of N use by farmers, each implemented under a range of sub-levels (low to high severity). Aggregated results show that all policies decreased N rates and N leaching, but this was associated with an exponential increase in economic costs. Achieving an N leaching reduction target of 20% has an estimated pollution control cost of 30–37 US$/ha, representing 147 million US$/year when scaled up to the state level, which is in the range of current government payments for existing conservation programs. Notably, such control of N losses would reduce the environmental impact of agriculture on water quality (externalities) by an estimated 524 million US$/year, representing an increase in society welfare of 377 million US$/year. Among the four policies, directly charging a fee on N leaching helped mitigate economic losses while improving the point source reduction effect (i.e., targeting fields that were leaching hotspots) and better internalization effect (i.e., targeting fields with higher environmental impact costs). This study provides actionable data to inform the development of cost-effective N fertilizer regulations by integrating changes in crop productivity and N losses in economic terms at the field level.

Effects of farmers’ behavioral characteristics on crop choices and responses to water management policies

Understanding farmers’ decision-making on crop choices and water use is essential for agricultural water resource management. However, previous studies have limited understanding of how farmers’ behavioral characteristics affect their crop choices and water use in agricultural systems. To fill this research gap, in this study we develop an agent-based model (ABM) that incorporates two types of behavioral characteristics (i.e., perception to the uncertainty in future crop prices, planting cost and precipitation, and tolerance to the variation of crop profits) to investigate their effects on crop choices and water use under the influence of water management policies. The ABM is applied to the Heihe River Basin (HRB), an arid endorheic river basin in northwestern China as a demonstration. The modeling results show that farmers with adventurous perceptions and high tolerance level (Type I) tend to choose high-profit crops. They are more likely to have a single-crop pattern with high crop profits and high water consumption. In comparison, farmers with cautious perceptions and low tolerance level (Type II) prefer steady profit crops. They typically pay more attention to the variation of crop profits, resulting in a mixed crop pattern with low crop profits and low water consumption. In addition, the two types of farmers exhibit varied responses to water management policies. The Type I farmers are more sensitive to the changes in the volume of water permits and irrigation efficiency, and as a result, are more sensitive to the changes of water management policies than the Type II farmers do. We also find that the effects of farmers’ behavioral characteristics vary at the irrigation district level, county level and entire study area level. These findings emphasize the importance of incorporating farmers’ behavioral characteristics into crop choice and water use models. The modeling result could provide policy implications for designing location-based water management policies that account for the heterogeneity in farmers’ behavioral characteristics and responses to water policies.

Impact of inoculation with local effective microorganisms on soil nitrogen cycling and legume productivity using composted broiler litter

Local effective microorganism (LEM) is an inoculant produced using leaf litter collected from forest floors near the location where it is to be utilized. While this locally-sourced inoculant is used around the world, more research is needed to fully understand the potential benefits or drawbacks of its use in agricultural systems. The objectives of this study were to observe the effects of combining LEM with composted broiler litter to fertilize edamame (Glycine max L.) on plant-available nitrogen, nematode trophic group communities, and soybean productivity. The study was carried out in a randomized, complete block design on piedmont soils in the southeastern United States comparing broiler litter composted with LEM, False-LEM or water (Control) treatments which were applied at the beginning of each growing season (June 2015, 2016, 2017). In the first year of the study, soil (0–10 cm) that received the LEM treatment mineralized greater amounts of N and mineralized N faster than CONT soils (P = 0.0665 and P = 0.0717), respectively, during one week of incubation. In year 2 (2016) plots experienced drought stress, with soil moistures as low as 2%. In LEM plots soil samples taken during the drought contained significantly greater populations of all nematodes, excluding Mononchidae when compared to the other treatments. When calculated per unit of soil N, measured after application of treatments, no differences in edamame soybean yield were observed between treatments. Combining LEM with composted broiler litter jump-started N mineralization early in growing seasons and maintained abundance of multiple nematode trophic groups during drought. This signifies LEM's potential to strengthen a soil's food web resistance to drought stress – providing more security for a functional agroecosystem under uncertain climate conditions.

C and P pool restoration by a no-tillage system on Brazilian Cerrado Oxisol in Piauí State.

The Cerrado soil is under constant modification, especially because of the use of agricultural systems, which affect soil carbon (C) and phosphorus (P) functioning. Thus, the objective of this study was to determine the C and P dynamics in Brazilian Cerrado Oxisol in Piauí State under natural and anthropic conditions, considering that conservational agricultural management and no-tillage systems can restore the C and P pools in that soil. Four soil samples with distinct characteristics (native Cerrado, NC; burned native Cerrado, BNC; conventional tillage agricultural system, CTS; and no-tillage agricultural system, NTS) were collected in the study area for chemical and physical laboratory analysis. The total organic carbon (TOC) concentrations found were 33gkg-1, 27gkg-1, 26gkg-1, and 20gkg-1 for CTS, NTS, NC, and BNC, respectively. The NTS had a total nitrogen (TN) concentration of 2.0gkg-1. The CTS had 33.4gkg-1 of soil-oxidizable C, followed by the NTS with 27.2gkg-1. In both studied layers, the NTS had an organic P concentration > 200mgkg-1. The higher TOC concentration in the CTS was because of the higher content of clay in comparison with that in the NTS. The organic P in the NTS was associated with a less labile fraction of C. Thus, despite the disturbance caused by agricultural systems, the adoption of the NTS could be an influential strategy in agricultural systems to restore soil organic functioning in the Brazilian Cerrado Oxisol in Piauí State.

SHui, an EU-Chinese cooperative project to optimize soil and water management in agricultural areas in the XXI century

This article outlines the major scientific objectives of the SHui project that seeks to optimize soil and water use in agricultural systems in the EU and China, by considering major current scientific challenges in this area. SHui (for Soil Hydrology research platform underpinning innovation to manage water scarcity in European and Chinese cropping systems) is large cooperative project that aims to provide significant advances through transdisciplinary research at multiple scales (plot, field, catchment and region). This paper explains our research platform of long-term experiments established at plot scale, approaches taken to integrate crop and hydrological models at field scale; coupled crop models and satellite-based observations at regional scales; decision support systems for specific farming situations; and the integration of these technologies to provide policy recommendations through socio-economic analysis of the impact of soil and water saving technologies. It also outlines the training of stakeholders to develop a basic common curriculum despite the subject being distributed across different disciplines and professions. As such, this article provides a review of major challenges for improving soil and water use in EU and China as well as information about the potential to access information made available by SHui, and to allow others to engage with the project.

EFICIÊNCIA DO USO DE NITROGÊNIO EM PLANTAS TRANSGÊNICAS DE TABACO COM ALTO ACÚMULO DE PROLINA

Increasing the nitrogen use efficiencyofcrop plants is a result of the improvement in the mechanisms involved in nitrogen uptake, translocation, assimilation and remobilization. In this study, tobacco plants with high accumulation of proline caused by the insertion of the VaP5CSF129Amutant gene under control of the constitutive promoter CaMV35S was used as a model to investigate the effect of overexpression of the transgene in the uptake and utilization of N. For this, an experiment was carried out in a completely randomized design, in a 2x5 factorial arrangement, with two genotypes (transgenic eventand untransformed control) and five levels of nitrogen fertilization (25, 50, 100, 200 and 400 kg N ha-¹), cultivated under greenhouse conditions. Plants were evaluated for height, number of leaves, dry mass, free proline content, nitrogencontent, total protein content and use of the applied N (efficiency of absorption -EAbs, efficiency of leaf utilization –EUtiland efficiency of plant use -EUN). The transgenic plantswith high proline accumulation were less efficient than the control plants in terms of nitrogen absorption (with lowerN levelsin root, leaves and wholeplant), which resulted in lower EAbs. There was no difference between the transgenic and control genotypesfor EUtil. However, the transgenic plants presented lower EUN in comparison tothe control plants. Our data showed thattransgenictobacco plants withhigh proline accumulation do not have potential for direct use in agricultural systems, since the alteration of the biochemical balance between the metabolisms of nitrogen and carbon did not result in plants with higher EUN.

Improving Phosphorus Fertility in Soil through Microbial Mediators

Microbes are an important element of the phosphorus cycle operative in the soil and play significant roles in transference of phosphorus between various soil phosphorus pools. Therefore, there has been continued interest in the usage of soil microbes to improve the phosphorus nutrition of plants and increase the overall efficiency of phosphorus use in agricultural systems. This interest originates from the fact that insufficiency of phosphorus is a common problem in soils all over the world, that a foremost cost for agricultural production is due to phosphate fertilizers and that the efficacy of phosphorus used by plants from soil applied phosphate fertilizers is very poor. Hence, with such issues the role of soil microbes in increasing phosphorus fertility in soils becomes more important. In this review several such aspects concerning the solubilisation and mobilization of soil phosphorus by microorganisms for enhancing soil fertility are discussed.

Efficacy of batch mode rotary drum composter for management of aquatic weed (Hydrilla verticillata (L.f.) Royle)

Invasive aquatic weed management is one of the biggest challenges in the field of solid waste management. Eichhornia crassipes, Pistia stratiotes and Hydrilla verticillata (L.f.) Royle pose some of the world's most noted aquatic weed problems. Previously reported studies on management of H. verticillata, a submersed aquatic plant, have shown that temporary removal, chemical treatment or biological control methods each have advantages and disadvantages. Removal programs that propose to compost harvested H. verticillata biomass may provide a novel technique to manage this issue. However, the properties of such compost as an agriculture resource are unclear. This study presents the different mix proportions of H. verticillata, cow dung and sawdust used for the composting of 550 L rotary drum composter. This work characterizes the biological, physicochemical, and respirometry properties of the various mixes over a 20-day composting period. The results suggest that the biomass of H. verticillata can be beneficially utilized to produce stable compost for potential use in agricultural systems.

Metals in Soil and Runoff from a Piedmont Hay Field Amended with Broiler Litter and Flue Gas Desulfurization Gypsum

Flue gas desulfurization gypsum (FGDG) from coal-fired power plants is readily available for agricultural use in many US regions. Broiler litter (BL) provides plant available N, P, and K but can be a source of unwanted As, Cu, and Zn. As a source of Ca and S, FGDG can reduce losses of P and other elements in runoff from BL-amended areas. Rainfall simulation plots (2.0 m) were established on a Piedmont Cecil soil growing 'Coastal' bermudagrass ( L.) for hay. Accumulation and transport of As, Cu, Cd, Cr, Hg, Pb, and Zn were evaluated after annual BL applications (13.5 Mg ha) with four FGDG rates (0, 2.2, 4.5, 9.0 Mg ha) and two FGDG treatments (0 and 9 Mg ha) without BL. Runoff As concentrations were sixfold greater with BL than without ( ≤ 0.01) and were similar to BL with FGDG at 2.2, 4.5 or 9.0 Mg ha ( ≤ 0.10). Runoff concentrations of target elements did not increase where FGDG was applied alone. After three annual applications of FGDG and BL, soil concentrations of As, Cr, Pb, Hg, and Cu were well below levels of environmental concern. Our findings indicate that runoff losses of As from BL application are not reduced with FGDG but support other research indicating no identifiable environmental risks from FGDG beneficial use in agricultural systems.

Physiological and phylogenetic variability of Mexican Metarhizium strains

Metarhizium Sorokin is a wide spread entomopathogenic fungal genus that is also a root symbiont and some isolates may be potentially useful in agriculture applications. Physiological variations applicable in biological control have not been fully evaluated in Mexican strains. This study identified 30 strains from different insect hosts and states of Mexico selected because they represent the main sugar cane and corn plantations of the country. Their thermotolerance profiles (8, 15, 28 and 35 °C), insect virulence (LT50 in Galleria mellonella (Linnaeus) (Lepidoptera: Pyralidae) larvae), possible association with plant roots, and phylogenetic placement (using 5′TEF, IGS sequence information, and RFLP analysis) were assessed. Results showed no cold-active strains and most showed restricted growth at 35 °C. Insect virulence bioassays against G. mellonella showed highly virulent strains. Most of the strains showed an ability to associate with roots of Phaseolus vulgaris (Burkart) (Fabales: Fabaceae). RFLP analysis with 5′TEF and Pr1 revealed three distinct genetic groups. Phylogenetic analysis identified the 30 strains as Metarhizium anisopliae. (Metchnikoff) Sorokin, M. robertsii (J.F. Bisch., Rehner & Humber), M. guizhouense (Q. T. Chen & H. L. Guo), or M. pinghaense (Q.T. Chen & H.L. Guo), as well as two strains that belong to a new clade (Metarhizium sp. indet. 1). These data demonstrate the complexity of Metarhizium species and the need to study their physiological and phylogenetic aspects for a more adequate assessment of their potential use in agricultural systems.

Low temperature circulating fluidized bed gasification and co-gasification of municipal sewage sludge. Part 2: Evaluation of ash materials as phosphorus fertilizer

The study is part 2 of 2 in an investigation of gasification and co-gasification of municipal sewage sludge in low temperature gasifiers. In this work, solid residuals from thermal gasification and co-gasification of municipal sewage sludge were investigated for their potential use as fertilizer. Ashes from five different low temperature circulating fluidized bed (LT-CFB) gasification campaigns including two mono-sludge campaigns, two sludge/straw mixed fuels campaigns and a straw reference campaign were compared. Experiments were conducted on two different LT-CFBs with thermal capacities of 100kW and 6MW, respectively. The assessment included: (i) Elemental composition and recovery of key elements and heavy metals; (ii) content of total carbon (C) and total nitrogen (N); (iii) pH; (iv) water extractability of phosphorus after incubation in soil; and (v) plant phosphorus response measured in a pot experiment with the most promising ash material. Co-gasification of straw and sludge in LT-CFB gasifiers produced ashes with a high content of recalcitrant C, phosphorus (P) and potassium (K), a low content of heavy metals (especially cadmium) and an improved plant P availability compared to the mono-sludge ashes, thereby showing the best fertilizer qualities among all assessed materials. It was also found that bottom ashes from the char reactor contained even less heavy metals than cyclone ashes. It is concluded that LT-CFB gasification and co-gasification is a highly effective way to purify and sanitize sewage sludge for subsequent use in agricultural systems.