Heat Treatments for Killing Apple Maggot Fly (Diptera: Tephritidae) Puparia for Application in Disinfesting Organic Yard Waste

Organic yard waste from western Washington, U.S. that may contain puparia of apple maggot fly, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), had been moved to central Washington for composting, threatening the $3 billion apple industry concentrated in that region. Heating waste to kill fly puparia before it is transported could be a solution to this problem. Here, we report results of studies in 2016-2021 that sought to identify a minimum heat treatment simulating that obtained using a low-pressure steam generator for maximizing kill of R. pomonella puparia. In two experiments, puparia were exposed to temperatures ramped linearly over 6 h from 21°C to 47.8, 51.1, 55.0, or 60.0°C in an oven. The 47.8, 51.1, and 55°C treatments did not achieve 100% mortality, although only one adult fly from 4,000 puparia was found in the 55°C treatment, while no puparia survived the 60°C treatment. In a third, similar experiment, no puparia out of 2,400 exposed to 55°C survived. In a fourth and final experiment conducted over 3 years, no puparia out of 61,223 exposed to a 6-h ramp from 21°C to 55°C followed by a 1-h hold time at 55°C produced flies. In addition, all puparia in this treatment died. Based on 42.3 to 69.8% control survival, 31,217 puparia were killed by this treatment with no survivors, for a probit 8.7190 level of security. Results suggest that the 55°C and 1-h hold time treatment here is close to the minimum heat regime needed for disinfesting organic waste of R. pomonella puparia.

Dramatic effect of black soldier fly larvae on fungal community in a compost

BACKGROUND

Black soldier fly larvae (BSFL) offer very good prospects for the production of cheap and high-quality dietary protein. This insect is able to consume low-quality substrates, including food waste. The properties and safety of the compost obtained are largely determined by its microbiome. However, while the bacterial component of the BSFL-compost microbiome has been much studied, little is known about its fungal component. In plant-based rearing substrates both the biomass and the metabolic activity of fungi often exceed the biomass and the activity of prokaryotes. So, the purpose of this study was to investigate the fungal community of the compost produced by BSF larvae reared on a food waste substrate.

RESULTS

Community structure was determined by metabarcoding of the ITS (internal transcribed spacer) region. Species composition and abundance were determined using the plating technique and subsequent identification of the isolated pure cultures. It was found that the primary mycobiome of the food waste substrate that was used consisted of 19 families, represented mainly by phytopathogenic and endophytic genera. Larva incubation led to the complete elimination of all mycelial fungi from the resulting compost. The final mycobiome consisted of only two yeast species, Pichia kudriavzevii and Diutina rugosa, with a total abundance of 1.2 × 10⁷  CFU g^-1 .

CONCLUSIONS

The rearing of BSFL led to the complete elimination of mycelial fungi from its feed substrate. The final compost lacked harmful fungi, including molds. This information may be crucial for BSF compost utilization. The phenomenon was also an interesting aspect of zoomicrobial interactions in nature and agriculture. © 2021 Society of Chemical Industry.

Dynamic Microstructure Assembly Driven by Lysinibacillus sp. LF-N1 and Penicillium oxalicum DH-1 Inoculants Corresponds to Composting Performance

The effects of Lysinibacillus sp. LF-N1 and Penicillium oxalicum DH-1 inoculants (LFPO group) on compost succession and the microbial dynamic structure of co-composting wheat straw and cow manure composting were investigated. The inoculants contributed to longer thermophilic stages, higher temperatures (62.8 °C) and lower microbial diversity in the LFPO treatment compared to the control group (CK). Moreover, LFPO inoculation increased the germination index and accelerated organic matter and lignocellulose degradation in the compost. Microbial analysis confirmed that the inoculants effectively altered the microbial communities. The predominant biomarkers for bacteria and fungi in inoculated compost were members of Lysinibacillus and Penicillium, respectively. Functional prediction showed greater lignocellulose degradation and less pathogen accumulation in the LFPO group. The cooccurrence network analysis showed that the network structure in LFPO compost was greatly simplified compared to that in CK. Bacterial cluster A was dominated by Lysinibacillus, and fungal cluster B was represented by Penicillium, which were significantly correlated with temperature and lignocellulose degradation, respectively (p < 0.05). These results demonstrated that the LF-N1 and DH-1 inoculants drove the bacterial and fungal assemblies to induce physicochemical property changes during cocomposting.

Collaborative Impact of Compost and Beneficial Rhizobacteria on Soil Properties, Physiological Attributes, and Productivity of Wheat Subjected to Deficit Irrigation in Salt Affected Soil

Plant growth and crop productivity under unfavorable environmental challenges require a unique strategy to scavenge the severely negative impacts of these challenges such as soil salinity and water stress. Compost and plant growth-promoting rhizobacteria (PGPR) have many beneficial impacts, particularly in plants exposed to different types of stress. Therefore, a field experiment during two successive seasons was conducted to investigate the impact of compost and PGPR either separately or in a combination on exchangeable sodium percentage (ESP), soil enzymes (urease and dehydrogenase), wheat physiology, antioxidant defense system, growth, and productivity under deficient irrigation and soil salinity conditions. Our findings showed that exposure of wheat plants to deficit irrigation in salt-affected soil inhibited wheat growth and development, and eventually reduced crop productivity. However, these injurious impacts were diminished after soil amendment using the combined application of compost and PGPR. This combined application enhanced soil urease and dehydrogenase, ion selectivity, chlorophylls, carotenoids, stomatal conductance, and the relative water content (RWC) whilst reducing ESP, proline content, which eventually increased the yield-related traits of wheat plants under deficient irrigation conditions. Moreover, the coupled application of compost and PGPR reduced the uptake of Na and resulted in an increment in superoxide dismutase (SOD), catalase (CAT), and peroxidase (POX) activities that lessened oxidative damage and improved the nutrient uptake (N, P, and K) of deficiently irrigated wheat plants under soil salinity. It was concluded that to protect wheat plants from environmental stressors, such as water stress and soil salinity, co-application of compost with PGPR was found to be effective.

Isolation and Characterization of Competitive Exclusion Microorganisms from Animal Wastes-Based Composts against Listeria monocytogenes

AIM

To isolate the slow-growing or viable but non-culturable competitive exclusion (CE) microorganisms from composts and then verify the anti-Listeria monocytogenes activities of those CE isolates in compost.

METHODS AND RESULTS

CE strains were isolated from composts using double- or triple-layer agar methods, purified, and then characterized. Both compost extracts and solid compost samples were spiked with a cocktail of 3 L. monocytogenes strains which were co-inoculated with or without CE strain cocktail and incubated at both 22°C and 35°C for 168 h. Results indicated that the addition of resuscitation promoting factor (Rpf) promoted the growth of slow-growing species from composts. About 50% of the isolated CE strains (n=40) were identified as Bacillus spp., 17 strains can inhibit more than ten tested L. monocytogenes strains, and 9 strains were motile and competitive biofilm formers. In compost extracts, the growth potentials of L. monocytogenes were reduced up to 2.2 logs when co-culturing with CE strains. In compost samples, the addition of CE strains reduced L. monocytogenes population by ca. 1.3 log CFU/g at 22°C after 24 to 168 h incubation.

CONCLUSION

Our modified double/triple-layer agar procedure with Rpf as growth supplement coupled with spot-on-lawn testing can be a quick and efficient method for isolating CE candidates from composts. The efficacy of CE strains against L. monocytogenes in compost extracts and compost samples was affected by compost type, nutrient level, and incubation temperature.

SIGNIFICANCE AND IMPACT OF THE STUDY

Compost is a rich source of CE microorganisms and compost-adapted CE microorganisms have the potential as a biological agent to control L. monocytogenes in agricultural environments.

Thermophilic Composting of Human Feces: Development of Bacterial Community Composition and Antimicrobial Resistance Gene Pool

In times of climate change, practicing sustainable, climate-resilient, and productive agriculture is of primordial importance. Compost from different resources, now treated as wastes, could be one form of sustainable fertilizer creating a resilience of agriculture to the adverse effects of climate change. However, the safety of the produced compost regarding human pathogens, pharmaceuticals, and related resistance genes must be considered. We have assessed the effect of thermophilic composting of dry toilet contents, green cuttings, and straw, with and without biochar, on fecal indicators, the bacterial community, and antibiotic resistance genes (ARGs). Mature compost samples were analyzed regarding fecal indicator organisms, revealing low levels of Escherichia coli that are in line with German regulations for fertilizers. However, one finding of Salmonella spp. exceeded the threshold value. Cultivation of bacteria from the mature compost resulted in 200 isolates with 36.5% of biosafety level 2 (BSL-2) species. The majority is known as opportunistic pathogens that likewise occur in different environments. A quarter of the isolated BSL-2 strains exhibited multiresistance to different classes of antibiotics. Molecular analysis of total DNA before and after composting revealed changes in bacterial community composition and ARGs. 16S rRNA gene amplicon sequencing showed a decline of the two most abundant phyla Proteobacteria (start: 36-48%, end: 27-30%) and Firmicutes (start: 13-33%, end: 12-16%), whereas the abundance of Chloroflexi, Gemmatimonadetes, and Planctomycetes rose. Groups containing many human pathogens decreased during composting, like Pseudomonadales, Bacilli with Bacillus spp., or Staphylococcaceae and Enterococcaceae. Gene-specific PCR showed a decline in the number of detectable ARGs from 15 before to 8 after composting. The results reveal the importance of sufficiently high temperatures lasting for a sufficiently long period during the thermophilic phase of composting for reducing Salmonella to levels matching the criteria for fertilizers. However, most severe human pathogens that were targeted by isolation conditions were not detected. Cultivation-independent analyses also indicated a decline in bacterial orders comprising many pathogenic bacteria, as well as a decrease in ARGs. In summary, thermophilic composting could be a promising approach for producing hygienically safe organic fertilizer from ecological sanitation.

Industrial Composting of Sewage Sludge: Study of the Bacteriome, Sanitation, and Antibiotic-Resistant Strains

Wastewater treatment generates a huge amount of sewage sludge, which is a source of environmental pollution. Among the alternatives for the management of this waste, industrial composting stands out as one of the most relevant. The objective of this study was to analyze the bacterial population linked to this process and to determine its effectiveness for the reduction, and even elimination, of microorganisms and pathogens present in these organic wastes. For this purpose, the bacteriome and the fecal bacteria contamination of samples from different sewage sludge industrial composting facilities were evaluated. In addition, fecal bacteria indicators and pathogens, such as Salmonella, were isolated from samples collected at key stages of the process and characterized for antibiotic resistance to macrolide, β-lactam, quinolone, and aminoglycoside families. 16S rRNA phylogeny data revealed that the process clearly evolved toward a prevalence of Firmicutes and Actinobacteria phyla, removing the fecal load. Moreover, antibiotic-resistant microorganisms present in the raw materials were reduced, since these were isolated only in the bio-oxidative phase. Therefore, industrial composting of sewage sludge results in a bio-safe final product suitable for use in a variety of applications.

Best practice for bio-waste collection as a prerequisite for high-quality compost

Due to its high content of humic substances, compost from bio-waste improves the structure and fertility of soils serving also as a sink for CO₂. But compost is also contaminated with numerous compounds, for example, plastics, glass particles, etc., mostly due to incorrect sorting by the waste producer, that is, households. The contamination even increases when covering areas of a high population density as is also evident from experience in Germany with a steadily increasing proportion of bio-waste. Only compost with high quality and minimum contamination is an acceptable fertilizer. A structured interview of experts investigated which measures or combinations of measures are best suitable to reduce the rate of misplaced materials in the organic waste. Only responsible persons were interviewed whose municipalities extensively collect separately bio-waste since years and have a low rate of unwanted materials. The questions focus on the identification of the misplacements according to their kind and quantity, the respective collection system, the regional statutes and their enforcement as well as the kind and extent of public awareness measures. The respective necessary measures are being discussed. This systemic approach can be transferred to other regions that intend to collect large quantities of bio-waste separately.

Functional and Taxonomic Effects of Organic Amendments on the Restoration of Semiarid Quarry Soils

The application of organic amendments to mining soils has been shown to be a successful method of restoration, improving key physicochemical soil properties. However, there is a lack of a clear understanding of the soil bacterial community taxonomic and functional changes that are brought about by these treatments. We present further metagenomic sequencing (MGS) profiling of the effects of different restoration treatments applied to degraded, arid quarry soils in southern Spain which had previously been profiled only with 16S rRNA gene (16S) and physicochemical analyses. Both taxonomic and functional MGS profiles showed clear separation of organic treatment amendments from control samples, and although taxonomic differences were quite clear, functional redundancy was higher than expected and the majority of the latter signal came from the aggregation of minor (<0.1%) community differences. Significant taxonomic differences were seen with the presumably less-biased MGS-for example, the phylum Actinobacteria and the two genera Chloracidobacterium (Acidobacteria) and Paenibacillus (Firmicutes) were determined to be major players by the MGS and this was consistent with their potential functional roles. The former phylum was much less present, and the latter two genera were either minor components or not detected in the 16S data. Mapping of reads to MetaCyc/BioCyc categories showed overall slightly higher biosynthesis and degradation capabilities in all treatments versus control soils, with sewage amendments showing highest values and vegetable-based amendments being at intermediate levels, matching higher nutrient levels, respiration rates, enzyme activities, and bacterial biomass previously observed in the treated soils. IMPORTANCE The restoration of soils impacted by human activities poses specific challenges regarding the reestablishment of functional microbial communities which will further support the reintroduction of plant species. Organic fertilizers, originating from either treated sewage or vegetable wastes, have shown promise in restoration experiments; however, we still do not have a clear understanding of the functional and taxonomic changes that occur during these treatments. We used metagenomics to profile restoration treatments applied to degraded, arid quarry soils in southern Spain. We found that the assortments of individual functions and taxa within each soil could clearly identify treatments, while at the same time they demonstrated high functional redundancy. Functions grouped into higher pathways tended to match physicochemical measurements made on the same soils. In contrast, significant taxonomic differences were seen when the treatments were previously studied with a single marker gene, highlighting the advantage of metagenomic analysis for complex soil communities.

Influence of Manure Application on the Soil Bacterial Microbiome in Integrated Crop-Livestock Farms in Maryland

As a traditional agricultural system, integrated crop-livestock farms (ICLFs) involve the production of animals and crops in a shared environment. The ICLFs in the mid-Atlantic region of the United States practice sustainable manure aging or composting processes to provide an on-farm source of soil amendment for use as natural fertilizer and soil conditioner for crop production. However, crop fertilization by soil incorporation of aged manure or compost may introduce different microbes and alter the soil microbial community. The aim of this study was to characterize the influence of aged or composted manure application on the diversity of soil bacterial community in ICLFs. Soil samples from six ICLFs in Maryland were collected before (pre-crop) and during the season (2020–2021) and used to analyze soil bacterial microbiome by 16S rDNA sequencing. Results showed that both phylum- and genus-level alterations of soil bacterial communities were associated with amendment of aged or composted manure. Particularly, Proteobacteria and Actinobacteria were enriched, while Acidobacteria, Bacteroidetes, Planctomycetes, Firmicutes, and Chloroflexi were reduced after manure product application. Meanwhile, the relative abundance of Bacillus was decreased, while two zoonotic pathogens, Salmonella and Listeria, were enriched by manure amendments. Overall, animal manure amendment of soil increased the phylogenetic diversity, but reduced the richness and evenness of the soil bacterial communities. Although manure composting management in ICLFs benefits agricultural sustainable production, the amendments altered the soil bacterial communities and were associated with the finding of two major zoonotic bacterial pathogens, which raises the possibility of their potential transfer to fresh horticultural produce crops that may be produced on the manured soils and then subsequently consumed without cooking.

Inactivation of indicator microorganisms and biological hazards by standard and/or alternative processing methods in Category 2 and 3 animal by-products and derived products to be used as organic fertilisers and/or soil improvers

The European Commission requested EFSA to assess if different thermal processes achieve a 5 log10 reduction in Enterococcus faecalis or Salmonella Senftenberg (775W) and (if relevant) a 3 log10 reduction in thermoresistant viruses (e.g. Parvovirus) as well as if different chemical processes achieve a 3 log10 reduction of eggs of Ascaris sp., in eight groups of Category 2 and 3 derived products and animal by-products (ABP). These included (1) ash derived from incineration, co-incineration and combustion; (2) glycerine derived from the production of biodiesel and renewable fuels; (3) other materials derived from the production of biodiesel and renewable fuels; (4) hides and skins; (5) wool and hair; (6) feathers and down; (7) pig bristles; and (8) horns, horn products, hooves and hoof products. Data on the presence of viral hazards and on thermal and chemical inactivation of the targeted indicator microorganisms and biological hazards under relevant processing conditions were extracted via extensive literature searches. The evidence was assessed via expert knowledge elicitation. The certainty that the required log10 reductions in the most resistant indicator microorganisms or biological hazards will be achieved for each of the eight groups of materials mentioned above by the thermal and/or chemical processes was (1) 99-100% for the two processes assessed; (2) 98-100% in Category 2 ABP, at least 90-99% in Category 3 ABP; (3) 90-99% in Category 2 ABP; at least 66-90% in Category 3 ABP; (4) 10-66% and 33-66%; (5) 1-33% and 10-50%; (6) 66-90%; (7) 33-66% and 50-95%; (8) 66-95%, respectively. Data generation on the occurrence and reduction of biological hazards by thermal and/or chemical methods in these materials and on the characterisation of the usage pathways of ABP as organic fertilisers/soil improvers is recommended.

Integrated Nutrient Management Enhances Productivity and Nitrogen Use Efficiency of Crops in Acidic and Charland Soils

Integrated Plant Nutrient System (IPNS) is practiced worldwide to maintain soil quality. Two field experiments were conducted in 2019 and 2020 in acidic and charland soils to assess the impact of different manures, viz., poultry manure (PM), vermicompost (VC), compost (OF), rice husk biochar (RHB), poultry manure biochar (PMB)-based IPNS, and dolomite over control on productivity and nitrogen use efficiency (NUE) of the Mustard-Boro-Transplanted Aman and Maize-Jute-Transplanted Aman cropping patterns, and on soil properties. The experiments were laid out in a randomized complete block design with four replications. The results showed that IPNS treatments significantly improved soil aggregate properties and total nitrogen in acidic soil, and bulk density in charland soil. In both years, IPNS treatments increased system productivity from 55.4 to 82.8% in acidic soil and from 43.3 to 115.4% in charland soil over that of control. IPNS and dolomite treatments increased nitrogen uptake from 35.5 to 105.7% over that of control and NUE in both soils in 2019 and 2020. PMB- and OF-based INPS treatments exhibited superior performances in both soils, and the impact was more prominent in 2020. Therefore, PMB- and OF-based IPNS can be recommended for maximizing system productivity and NUE with concurrent improvement of physicochemical properties of acidic and charland soils.

Microbial succession of lignocellulose degrading bacteria during composting of corn stalk

The discarding and burning of corn stalks in the fields after harvesting lead to environmental pollution and waste of resources. Composting is an effective way to disposal of the crop straws. Composting is a complex biochemical process and need a detail studied in cold region. Hence, the succession process of bacteria and Actinomycetes in the process of corn stalk composting in cold region was studied by 16SrRNA. Alpha diversity analysis showed that the detection results could represent the real situation. The bacterial community diversity from high to low was F50 > F90 > F0 > F10 > F20. The results of beta analysis showed that F20 and F50 had the most similar microbial structure at the phylum level, and the difference between F0 and F20 was the largest. The dominant microbes changed from Proteobacteria and Bacteroidetes in F0 in heating stage to Firmicutes and Proteobacteria, Actinobacteria and Firmicutes in F10 during early high temperature stage, and Actinobacteria, Proteobacteria and Bacteroidetes in cooling and post composting phases. Actinobacteria and Firmicutes were the dominant bacteria in the whole composting process. In the composting process, the microbial community was mainly involved in amino acid metabolism related to nitrogen transformation and carbohydrate metabolism related to lignocellulose degradation. Lignin and hemicellulose were mainly degraded in thermophilic stage. The conversion of nitrogen and degradation of cellulose occurred mainly in the early stages of composting. The research will be helpful to understand the biochemical process of composting in cold region.

Compost as an untapped niche for thermotolerant yeasts capable of high-temperature ethanol production

Efficient bioethanol production from lignocellulosic biomass requires thermotolerant yeasts capable of utilizing multiple sugars, tolerating inhibitors and fermenting at high temperatures. In this study, 98 thermotolerant yeasts were isolated from nine compost samples. We selected 37 yeasts that belonged to 11 species; 31 grew at 45°C; 6 strains grew at 47°C, while 9 yeasts could utilize multiple sugars. Many yeast isolates showed high ethanol production in the range of 12-24 g l^-1 , with fermentation efficiencies of 47-94% at 40°C using 5% glucose. Kluyveromyces marxianus CSV3.1 and CSC4.1 (47°C), Pichia kudriavzevii CSUA9.3 (45°C) produced 21, 22 and 23 g l^-1 of ethanol with efficiencies of 83, 87 and 90%, respectively, using 5% glucose. Among these yeasts, K. marxianus CSC4.1 and P. kudriavzevii CSUA9.3 exhibited high tolerance against furfural, 5-HMF, acetic acid and ethanol. These two strains produced high amounts of ethanol from alkali-treated RS, with 84 and 87% efficiency via separate hydrolysis and fermentation; 76 and 74% via simultaneous saccharification and fermentation at 47 and 45°C, respectively. Therefore, this study demonstrates compost as a potential anthropogenic niche for multiple sugar-utilizing, inhibitor-tolerant ethanologenic yeasts suitable for high-temperature ethanol production via SHF of rice straw.

Antibiotic resistance genes in layer farms and their correlation with environmental samples

Livestock farms are generally considered to be the important source of antibiotic resistance genes (ARGs). It is important to explore the spread of ARGs to reduce their harm. This study analyzed 13 resistance genes belonging to 7 types in 68 samples of layer manure including different stages of layer breeding, layer manure fertilizer, and soil from 9 laying hen farms in Guangdong Province. The detection rate of antibiotic resistance genes was extremely high at the layer farm in manure (100%), layer manure fertilizer (100%), and soil (> 95%). The log counts of antibiotic resistance genes in layer manure (3.34-11.83 log copies/g) were significantly higher than those in layer manure fertilizer (3.45-9.80 log copies/g) and soil (0-7.69 log copies/g). In layer manure, ermB was the most abundant antibiotic resistance gene, with a concentration of 3.19 × 10⁹- 6.82 × 10¹¹ copies/g. The average abundances of 5 antibiotic resistance genes were above 10¹⁰ copies/g in the descending order ermB, sul2, tetA, sul1, and strB. The relative abundances of ARGs in layer manure samples from different breeding stages ranked as follows: brooding period (BP), late laying period (LL), growing period (GP), early laying period (EL), and peak laying period (PL). There was no significant correlation between the farm scale and the abundance of antibiotic resistance genes. Moreover, the farther away from the layer farm, the lower the abundance of antibiotic resistance genes in the soil. We also found that compost increases the correlation between antibiotic resistance genes, and the antibiotic resistance genes in soil may be directly derived from layer manure fertilizer instead of manure. Therefore, when applying layer manure fertilizer to cultivated land, the risk of antibiotic resistance genes pollution should be acknowledged, and in-depth research should be conducted on how to remove antibiotic resistance genes from layer manure fertilizer to control the spread of antibiotic resistance genes.

Alleviation of Chlorpyrifos Toxicity in Maize (Zea mays L.) by Reducing Its Uptake and Oxidative Stress in Response to Soil-Applied Compost and Biochar Amendments

Chlorpyrifos (CP) is a pesticide used extensively in agricultural crops. Residual CP has been found in a variety of soils, vegetables and fruits indicating a serious danger to humans. Therefore, it is necessary to restrict its entry into agricultural products for food safety. A wire-house pot experiment was conducted with maize plants in biochar- and compost-amended soil (at 0.25% and 0.50%, respectively, in weight-by-weight composition) contaminated with 100 and 200 mg kg⁻¹ of CP, respectively. Results indicated toxicity at both CP levels (with 84% growth reduction) at CP 200 mg kg⁻¹. However, application of compost and biochar at the 0.50% level improved the fresh weight (2.8- and 4-fold, respectively). Stimulated superoxide dismutase (SOD) and peroxidase (POX) activities and depressed catalase (CAT) activity were recorded in response to CP contamination and were significantly recovered by the amendments. Both amendments significantly decreased the CP phytoavailability. With biochar, 91% and 76% reduction in the CP concentration in maize shoots and with compost 72% and 68% reduction was recorded, at a 0.50% level in 100 and 200 mg kg⁻¹ contaminated treatments respectively. Compost accelerated the CP degradation in postharvest soil. Therefore, biochar and compost amendments can effectively be used to decrease CP entry in agricultural produce by reducing its phytoavailability.

Mulches Used in Highbush Blueberry and Entomopathogenic Nematodes Affect Mortality Rates of Third-Instar Popillia japonica

Simple Summary

Japanese beetle is a serious pest of many crops, including blueberry. While the adult beetles feed on leaves, the grubs (immatures) feed on plant roots and can cause wilting and reduced plant growth. Farmers rely on insecticides to control Japanese beetle, but nematodes that attack and kill grubs in the soil may be as effective as insecticides in some cases. Mulches of compost, woodchips, sawdust, and tree bark are commonly used in blueberry production, but it is not known how mulches affect Japanese beetle grubs or the effectiveness of beneficial nematodes to control grubs. We placed grubs in soil beneath different mulches in the laboratory and tested two nematodes. The species H. bacteriophora killed almost all grubs in all mulches, but S. scarabaei was not as effective and was more affected by mulch type. A mulch of compost + woodchips and sawdust caused 60% grub mortality without adding nematodes. In a field experiment during October, the nematodes caused 50% grub mortality, which was lower than expected and likely due to cool soil temperatures. We recommend using H. bacteriophora for Japanese beetle grub management in blueberry, regardless of the mulch type being used.

Abstract

Popillia japonica Newman (Japanese beetle) is an invasive, polyphagous pest in North America, as adults feed on plant foliage and larvae on roots. Management in crops relies on foliar and soil applications of insecticides, but entomopathogenic nematodes (EPN) are effective biocontrol agents. In highbush blueberry, mulches (composts, woodshavings, sawdust, bark) are used for weed control and fertility. Therefore, our objective was to determine the effects of Heterorhabditis bacteriophora and Steinernema scarabaei on third-instar P. japonica in substrates commonly used as mulches in blueberry. In containers in the laboratory, larval mortality was 90–100% with H. bacteriophora for all substrates, but rates with S. scarabaei were lower and variable among substrates. A mixture of municipal compost + woodchips/sawdust resulted in 60% larval mortality without adding EPN, but few nematodes were recovered, indicating other causes of death. In a field microplot experiment in October, larval mortality rates were 50% at most for all EPN and substrate type combinations, likely due to lower than optimal soil and substrate temperatures for EPN survival and infectivity. Overall, a compost and woodchip/sawdust mulch should help suppress P. japonica populations in blueberry, and applying H. bacteriophora when temperatures are optimal to mulches can provide excellent larval control.

Pharmaceuticals and Their Main Metabolites in Treated Sewage Sludge and Sludge-Amended Soil: Availability and Sorption Behaviour

This work evaluated the availability and sorption behaviour of four pharmaceuticals and eight of their metabolites in sewage sludge and sludge-amended soil. Digested sludge and compost were evaluated. The highest levels found in digested sludge corresponded to caffeine (up to 115 ng g⁻¹ dm), ibuprofen (45 ng g⁻¹ dm) and carbamazepine (9.3 ng g⁻¹ dm). The concentrations measured in compost were even lower than in digested sludge. No compound was detected in sludge-amended soils. This fact could be due to the dilution effect after sludge application to soil. Different adsorption capacities in sludge–soil mixtures were measured for the studied compounds at the same spike concentration. In general, except for paraxanthine and 3-hydroxycarbamazepine, the metabolite concentrations measured in the mixtures were almost two-fold lower than those of their parent compounds, which can be explained by their mobility and lixiviation tendency. The log K_d ranged from −1.55 to 1.71 in sludge samples and from −0.29 to 1.18 in soil–sludge mixtures. The log K_d values calculated for compost were higher than those calculated for digested sludge. The obtained results implied that the higher organic carbon content of compost could influence soil contamination when it is applied to soil.

Dynamics of bacterial functional genes and community structures during rhizoremediation of diesel-contaminated compost-amended soil

The objective of this study was to characterize the effects of organic soil amendment (compost) on bacterial populations associated with petroleum hydrocarbon (PH) degradation and nitrous oxide (N₂O) dynamics via pot experiments. Soil was artificially contaminated with diesel oil at total petroleum hydrocarbon (TPH) concentration of 30,000 mg·kg-soil^-1 and compost was mixed with the contaminated soil at a 1:9 ratio (w/w). Maize seedlings were planted in each pot and a total of ten pots with two treatments (compost-amended and unamended) were prepared. The pot experiment was conducted for 85 days. The compost-amended soil had a significantly higher TPH removal efficiency (51.1%) than unamended soil (21.4%). Additionally, the relative abundance of the alkB gene, which is associated with PH degradation, was higher in the compost-amended soil than in the unamended soil. Similarly, cnorB and nosZ (which are associated with nitric oxide (NO) and N₂O reduction, respectively) were also highly upregulated in the compost-amended soil. Moreover, the compost-amended soil exhibited higher richness and evenness indices, indicating that bacterial diversity was higher in the amended soil than in the unamended soil. Therefore, our findings may contribute to the development of strategies to enhance remediation efficiency and greenhouse gas mitigation during the rhizoremediation of diesel-contaminated soils.

Biochar and Hyperthermophiles as Additives Accelerate the Removal of Antibiotic Resistance Genes and Mobile Genetic Elements during Composting

Sewage treatment plants are known as repositories of antibiotic resistance genes (ARGs). Adding biochar and inoculating with exogenous microbial agents are common ways to improve the quality of compost. However, little is known about the effects of these exogenous additives on the fate of ARGs during composting and the related mechanisms. In this study, municipal sludge was taken as the research object to study the ARG-removal effects of four composting methods: ordinary compost (CT), compost with hyperthermophiles (HT), compost with hyperthermophiles and 2.0% biochar (HT2C) and compost with hyperthermophiles and 5.0% biochar (HT5C). Real-time quantitative PCR (qPCR) and 16S rRNA high-throughput sequencing were conducted to analyze the ARGs, MGEs and bacterial community. After composting, the abundance of ARGs in CT was reduced by 72.7%, while HT, HT2C and HT5C were reduced by 80.7%, 84.3% and 84.8%, respectively. Treatments with different proportions of biochar added (HT2C, HT5C) had no significant effect on the abundance of ARGs. Network analysis showed that Firmicutes and Nitrospirae were positively associated with most ARGs and may be potential hosts for them. In addition, redundancy analysis further showed that the class 1 integrase gene (intI1), pH and organic carbon had a greater effect on ARGs. Our findings suggested that the combination of hyperthermophiles and biochar during the composting process was an effective way to control ARGs and mobile genetic elements (MGEs), thus inhibiting the spread and diffusion of ARGs in the environment and improving the efficiency of treating human and animal diseases.

Water productivity, yield and agronomic attributes of maize crop in response to varied irrigation levels and biochar-compost application

BACKGROUND

Due to the rapid increase in world population, the demand for freshwater is increasing day by day. There is also immense pressure on the agriculture sector to produce more food with limited supplies of water. About 75% of freshwater is used in crop production out of which 63% is lost due to poor farm practices and evapotranspiration. Enhancement of crop water productivity for sustainable agriculture production especially in areas having water scarcity plausibly contributes towards the solution of water scarcity.

RESULTS

The combined application of biochar and compost has a highly significant impact on maize yield with increased grain production, i.e. 6.44 and 6.52 t ha^-1 at 60% irrigation level with combined application of biochar and compost as compared with control at 6.39 and 6.44 t ha^-1 at 100% irrigation level in autumn and spring seasons, respectively, by saving 40% of water. Furthermore, the highest value of water productivity (1.51 and 1.16 kg m^-3 ) was achieved at 60% irrigation level with combined application of soil amendments. Also, cost-benefit analysis has shown highest values of net benefit with soil organic amendments.

CONCLUSIONS

It is concluded that addition of biochar and compost to soil has the potential to increase crop yield and growth even at low irrigation levels by enhancing water use efficiency. © 2021 Society of Chemical Industry.

Pyrrolizidine Alkaloids in the Food Chain: Is Horizontal Transfer of Natural Products of Relevance?

Recent studies have raised the question whether there is a potential threat by a horizontal transfer of toxic plant constituents such as pyrrolizidine alkaloids (PAs) between donor-PA-plants and acceptor non-PA-plants. This topic raised concerns about food and feed safety in the recent years. The purpose of the study described here was to investigate and evaluate horizontal transfer of PAs between donor and acceptor-plants by conducting a series of field trials using the PA-plant Lappula squarrosa as model and realistic agricultural conditions. Additionally, the effect of PA-plant residues recycling in the form of composts or press-cakes were investigated. The PA-transfer and the PA-content of soil, plants, and plant waste products was determined in form of a single sum parameter method using high-performance liquid chromatography mass spectroscopy (HPLC-ESI-MS/MS). PA-transfer from PA-donor to acceptor-plants was frequently observed at low rates during the vegetative growing phase especially in cases of close spatial proximity. However, at the time of harvest no PAs were detected in the relevant field products (grains). For all investigated agricultural scenarios, horizontal transfer of PAs is of no concern with regard to food or feed safety.

Biodegradation and Structural Modification of Humic Acids in a Compost Induced by Fertilization with Steelmaking Slag under Coastal Seawater, as Detected by TMAH-py-GC/MS, EEM and HPSEC Analyses

The compost's humic acid (HA) content decreased when it was fertilized in coastal seawater with steelmaking slag, as confirmed. This study clarified the cause for this change by a detailed analysis of the structural changes in HAs based on the TMAH-py-GC/MS, HPSEC, and 3D-EEM spectra. An increase in the levels of pyrolysates of tannic acid with a low polymerization degree was attributed to the biodegradation of a high polymerized aromatic structure. Moreover, analyses of 3D-EEM, supported by HPSEC, indicated that approximately 20 kDa of the fluorescent matter was generated at the protein-like peaks (Ex/Em = 220/340 and 275/350 nm) in HAs derived from a mixture of compost with steelmaking slag. It would be caused due to the formation of HAs from the bacterial by-product by a catalytic reaction of the steelmaking slag. From these findings reported herein, we conclude that bio-degradation was a major reason for the decreased HA content, and the formation of HA from a part of the degradation products. This would be a reason for the structural modification of HA under the seawater condition.

[Different Responses of Soil Dissolved Organic Matter to Different Types of Compost]

This study explored the responses of soil dissolved organic matter (DOM) to the application of different types of compost using a soil sample without compost as a control. Ultraviolet and fluorescence spectrum technology and EEM-PARAFAC was used to analyze DOM structure and driving factors in soil added with different proportion of cow dung compost (SCC), food and kitchen waste compost (SFC), and sludge compost (SCC). Compared with the control group, contents of AN, NH₄⁺-N, DOC, and SOM in soil added with compost were significantly increased, and contents of SOM and DOC increased with the increasing of compost amount. When added compost in the same proportion, contents of AN, NO₃^--N, and DOC in SCC and SFC were significantly higher than those in SSC, while contents of NH₄⁺-N and SOM were higher in SSC. The results of spectral analysis showed that the structure of conjugated benzene ring, hydrophobic component, quinone group, and chromogenic component in DOM of soil added with compost were significantly increased, the transition of unsaturated organic molecule (π→π^*) was more active, the molecular weight of DOM increased, and the degree of humification was enhanced. When the amount of compost added is 5%, the influence of food and kitchen waste compost on DOM structure was greatest among three types of compost. At 10% and 20%, sludge compost had the greatest impact on DOM structure. The results of EEM-PARAFAC analysis showed that the relative content of fulvic acid-like substances with low molecular in DOM of soil added with compost was increased, while the relative content of proteoid-like substances decreased. 2D-COS analysis showed that compost affected the change order of fluorescence components in DOM. SCC and SFC were as follows:proteoid-like > fulvic acid-like > humus-like; in SSC, it was fulvic acid-like > proteoid-like > humus-like. The enhance of humification and the decrease of relative content of protein-like substances in DOM were related to increased DOC and AN, the relative content of humus-like in low molecular weight was positively correlated with the content of NO₃^--N, and the relative content of macromolecule fulvic acid-like was increased due to the input of SOM from compost.

Positive long-term impacts of restoration on soils in an experimental urban forest

As urbanization increases worldwide, investments in nature-based solutions that aim to mitigate urban stressors and counter the impacts of global climate change are also on the rise. Tree planting on degraded urban lands-or afforestation-is one form of nature-based solution that has been increasingly implemented in cities around the world. The benefits of afforestation are, however, contingent on the capacity of soils to support the growth of planted trees, which poses a challenge in some urban settings where unfavorable soil conditions limit tree performance. Soil-focused site treatments could help urban areas overcome impediments to afforestation, yet few studies have examined the long-term (>5 yr) effects of site treatments on soils and other management objectives. We analyzed the impacts of compost amendments, interplanting with shrubs, and tree species composition (six species vs. two species) on soil conditions and associated tree growth in 54 experimental afforestation plots in New York City, USA. We compared baseline soil conditions to conditions after 6 yr and examined changes in the treatment effects from 1 to 6 yr. Site treatments and tree planting increased soil microbial biomass, water holding capacity, and total carbon and nitrogen, and reduced soil pH and bulk density relative to baseline conditions. These changes were most pronounced in compost-amended plots, and the effects of the shrub and species composition treatments were minimal. In fact, compost was key to sustaining long-term changes in soil carbon stocks, which increased by 17% in compost-amended plots but declined in unamended plots. Plots amended with compost also had 59% more nitrogen than unamended plots, which was associated with a 20% increase in the basal area of planted trees. Improvements in soil conditions after 6 yr departed from the initial trends observed after 1 yr, highlighting the importance of longer-term studies to quantify restoration success. Altogether, our results show that site treatments and tree planting can have long-lasting impacts on soil conditions and that these changes can support multiple urban land management objectives.