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Biofilm Formation and Genetic Diversity of Microbial Communities in Anaerobic Batch Reactor with Polylactide (PLA) Addition
In this paper, an anaerobic digestion (AD) study was conducted on confectionery waste with granular polylactide (PLA) as a cell carrier. Digested sewage sludge (SS) served as the inoculum and buffering agent of systems. This article shows the results of the analyses of the key experimental properties of PLA, i.e., morphological characteristics of the microstructure, chemical composition and thermal stability of the biopolymer. The evaluation of quantitative and qualitative changes in the genetic diversity of bacterial communities, performed using the state-of-the-art next generation sequencing (NGS) technique, revealed that the material significantly enhanced bacterial proliferation; however, it does not change microbiome biodiversity, as also confirmed via statistical analysis. More intense microbial proliferation (compared to the control sample, without PLA and not digested, CW–control, CW–confectionery waste) may be indicative of the dual role of the biopolymer—support and medium. Actinobacteria (34.87%) were the most abundant cluster in the CW–control, while the most dominant cluster in digested samples was firmicutes: in the sample without the addition of the carrier (CW–dig.) it was 68.27%, and in the sample with the addition of the carrier (CW + PLA) it was only 26.45%, comparable to the control sample (CW–control)—19.45%. Interestingly, the number of proteobacteria decreased in the CW–dig. sample (17.47%), but increased in the CW + PLA sample (39.82%) compared to the CW–control sample (32.70%). The analysis of biofilm formation dynamics using the BioFlux microfluidic system shows a significantly faster growth of the biofilm surface area for the CW + PLA sample. This information was complemented by observations of the morphological characteristics of the microorganisms using fluorescence microscopy. The images of the CW + PLA sample showed carrier sections covered with microbial consortia.
The Response of the Mycobiome to the Biofumigation of Replanted Soil in a Fruit Tree Nursery
In a long-term monoculture with fruit trees and tree nurseries, it is necessary to regenerate the soil due to the risk of apple replant disease (ARD). The occurrence of ARD is manifested in the structure of the mycobiome. The assumption of our experiment was that the use of oil radish (Raphanus sativus var. oleifera), white mustard (Sinapis alba), and marigold (Tagetes patula L.) as phytosanitary plants for biofumigation would provide crops with nutrients, improve soil physicochemical properties, and influence the diversity of microbiota, including fungal networks, towards a beneficial mycobiome. Metagenomic analysis of fungal populations based on the hypervariable ITS1 region was used for assessing changes in the soil mycobiome. It showed that biofumigation, mainly with a forecrop of marigold (Tagetes patula L.) (R3), caused an improvement in soil physicochemical properties (bulk density and humus) and the highest increase in the abundance of operational taxonomic units (OTUs) of the Fungi kingdom, which was similar to that of agriculturally undegraded soils, and amounted to 54.37%. In this variant of the experiment, the most OTUs were identified at the phylum level, for Ascomycota (39.82%) and Mortierellomycota beneficial fungi (7.73%). There were no such dependencies in the soils replanted with forecrops of oilseed radish (Raphanus sativus var. oleifera) and white mustard (Sinapis alba). Biofumigation with marigold and oil radish contributed to a reduction in the genus Fusarium, which contains several significant plant-pathogenic species. The percentages of operational taxonomic units (OTUs) of Fusarium spp. decreased from 1.57% to 0.17% and 0.47%, respectively.
Response of Soil Microorganisms to and Yield of Spelt Wheat following the Application of Bacterial Consortia and the Subsequent Effect of Cover Crops in Organic Farming
In modern agriculture, more and more attention is being paid to the use of microorganisms that can increase crop productivity and quality even under adverse weather conditions. Due to the declining biodiversity of crops and the occurrence of soil erosion and nutrient losses, the introduction of cover crops (CC) can be a positive crop management technique. In the field study presented here, the effect of growing spring barley with CCs applied simultaneously with bacterial consortia on the ratio of the total number of bacteria to actinobacteria (B/A) and the number of fungi in the soil was evaluated. The biomass yield of CCs and the subsequent effect on the yield of spelt wheat grown with the application of bacterial consortia were also evaluated. The bacterial consortia applied included consortium 1, comprising Bacillus subtilis, Bacillus amyloliquefaciens, and Pseudomonas fluorescens, and consortium 2, comprising Bacillus subtilis, Bacillus amyloliquefaciens, Pseudomonas fluorescens, and Azotobacter chroococcum. The CCs were red clover, red clover + Italian ryegrass, and Italian ryegrass. The most favorable B/A ratio and the highest number of fungi were obtained after growing spring barley with a CC consisting of a mixture of red clover and Italian ryegrass when using bacterial consortium 2. These conditions additionally had the most favorable influence on spelt wheat. The combination of such a forecrop with the application of bacterial consortium 2 resulted in the highest yields of spelt wheat.
The Use of a Composition of Bacterial Consortia and Living Mulch to Reduce Weeds in Organic Spring Barley Cultivation as an Element of Sustainable Plant Production
Weed infestation of cereal crops in organic farming is becoming a serious problem in agriculture. Sustainable agriculture requires the search for and implementation of crop management techniques that will reduce weeds without negatively impacting the environment. This research refers to the principles of integrated plant protection in sustainable agriculture, allowing the use of chemical plant protection products to be limited to the absolute minimum. Technology for growing spring barley based on the use of bacterial consortia in combination with living mulch (LM) can be an interesting approach to this problem. The aim of this three-year field research was to determine the effects of bacterial consortia and LM on the level of weed infestation in the organic spring barley crop. Two factors were tested in the experiment: bacterial consortia factors: control (without bacterial consortia); 1—Bacillus megaterium var. phosphaticum and Arthrobacter agilis; 2—Bacillus subtilis, Bacillus amyloliquefaciens, and Pseudomonas fluorescens; and LM: control (without LM); red clover; red clover + Italian ryegrass; and Italian ryegrass. This research demonstrated that the bacterial consortia tested significantly reduced both the biomass and number of weeds, including the following dominant weeds: Chenopodium album, Sinapis arvensis, Elymus repens, and Tripleurospermum inodorum. The use of LM also significantly reduced the weed infestation of spring barley stands. The lowest biomass and number of weeds, with the exception of Elymus repens, were recorded on objects with LM Italian ryegrass in spring barley in combination with bacterial consortium 2. The introduction of cultivation with LM Italian ryegrass or its mixture with red clover and the use of bacteria should be recommended for the practice of sustainable agriculture, which will reduce weeds through an ecological method.
Ocena jakościowych i ilościowych zmian mikrobiomu bakteryjnego w procesie beztlenowego rozkładu materii organicznej
Spatial-Temporal Differentiation of Soil Biochemical Parameters and Their Relationship with Nitrogen Resources during the Vegetation Period of Selected Crops
Understanding the spatial–temporal variability of soil enzymatic activity and its relationship with nitrogen (N) resources in the soil and crop yield is crucial in rational management practices of mineral fertilization. The scarcity of comprehensive studies on geostatic analyses of agricultural soils and plant yields, which would take into account both temporal and spatial variability, was the reason for undertaking this research. The aim of this study was to determine the spatial and temporal variability of the activity of soil enzymes, such as acid (PAC) and alkaline (PAL) phosphatases, urease (URE) and protease (PROT), the content of N-NH4 (ammonium ions), N-NO3 (nitrate ions), phosphorus (P), pH, moisture, as well as crop yield on a conventionally managed farmland of 40 ha. During the two-year experiment, soil samples were collected from 37 measurement points. Wheat was the first tested crop, followed by oilseed rape. It was shown that all the tested soil parameters showed temporal and spatial variability, and a significant number of them were significantly higher in July. The creation of raster maps showing the distribution of the tested parameters allowed for the observation of the considerable activity of PAC, PAL, URE, and PROT, as well as a high application of N-NO3 in the southern part of the field during the growth of the plants. The statistical analysis revealed a negative interaction between the N-NH4 and N-NO3 and the urease in the soil under the cultivation of plants. The pH and the percentage of moisture in the soil also had higher values in the south of the field. This pointed to the existence of separate production zones in the south-central part of the field, characterized by a higher yield of wheat and rape. On the basis of the conducted research, it was unequivocally stated that the values of enzymatic and chemical parameters of the soil were reflected in the size of the yield obtained, which allows conclusions to be drawn with respect to the rational management of N in the production process, laying the foundations for precision agriculture.
Sustainable Use of Organic Matter Obtained from the Bottom of a Post-Mining Pit Reservoir—A Case Study on the Creation of Raduszyn Lake in Poland
According to historical sources, a watermill existed in the valley of the Trojanka River on the north-western shore of Raduszyn Lake from the 15th century. Its dams lasted for centuries causing the water flow through the Raduszyn reservoir to slow down and deposit various mineral fractions in it. The aim of paper was to develop a scientific background for the sustainable management of organic matter extracted from the peat top and from deeper layers that are unsuitable for direct use, that is, decomposed peat. A SWOT (strengths, weaknesses, opportunities, threats) analysis was used to describe ways of restoration of the water reservoir alongside the characterization of organic matter and the financial condition of the studied enterprise. For the use of the studied material as a homogeneous substrate for plant cultivation, the contents of nitrogen, phosphorus, potassium, and copper were insufficient, whilst calcium was excessive. Microbiological analyses of the organic materials intended as an additive for horticultural substrates confirmed the presence of plant growth-promoting bacteria. The occurrence of such microorganisms in the substrate can limit the use of mineral fertilizers and chemical plant protection products. The results of the research can be an example for enterprises restoring or creating water reservoirs by extraction of organic matter, which is often considered as waste that generates costs and does not bring financial benefits. Such a measure can be used to improve the efficiency of water reservoir restoration enterprises and at the same time contribute to sustainable land development.
A Case Study on the Effect of Foliar Nitrogen Fertilization on the Microbiological and Biochemical State of the Soil and the Uptake of Macro- and Microelements by Winter Triticale (Triticosecale)
Due to the increasing demand for food, the agricultural sector is facing a huge challenge related to its production without having a negative impact on the environment. The above issues are regulated by the current EU policy, indicating the need to conduct plant production by the European Green Deal strategy (2020), based on reducing the use of chemical plant-protection products by 50% and reducing the level of mineral fertilization by 20% by 2030. Using appropriate techniques of applying mineral fertilizers, which have a positive effect on the development and activity of soil microorganisms, the availability of nutrients in the soil can be increased while reducing fertilizer applications. This study aims to show whether the use of foliar nitrogen fertilizers in combination with sulfur in a two-year field experiment with triticale stimulates the multiplication of selected groups of microorganisms and the level of soil enzymatic activity. In addition, effects on the content of available forms of nutrients in the soil, triticale yield, and total nutrient uptake were analyzed. It is shown that the applied foliar fertilizers enriched with sulfur, compared to fertilization with ammonium nitrate, contributed to a 100% increase in the number of analyzed groups of microorganisms, urease, and alkaline phosphatase activity; a 44% increase in dehydrogenase activity; and a 15% increase in acid phosphatase activity. The hybrid application technique, with reduced doses of nitrogen fertilizers enriched with sulfur by 20 and 25%, resulted in grain yields exceeding 8 t/ha. Moreover, compared to conventional fertilization based on ammonium nitrate, an increase in the grain yield of triticale was obtained in the range of 16 to 24%, as well as an increase in the accumulation of nutrients in the plant. It is shown that foliar fertilization is a promising alternative to standard fertilization techniques.
Diversity of Bacterial Communities in Horse Bean Plantations Soils with Various Cultivation Technologies
Modern agriculture should limit its degrading impact on the soils, the natural environment, and the climate. No-tillage soil cultivation technologies, which have been in use for many years and are constantly being improved, are a good example of these actions; although, in-depth studies on their impact on the soil microbial community are currently scarce. The aim of our study was to evaluate the effect of cultivation technology on the soil bacterial community to assess differences that can be reflected in the environmental and agricultural functionality, identifying possible bacterial species with ecological properties. In this context, the composition of bacterial communities (at the phyla, order, class, and species levels) was evaluated under different conditions, such as conventional tillage (CT) (plophing), reduced tillage (RT) (stubble cultivator), strip tillage (ST), and no-tillage (direct sowing on stubble and fallow buffer zone of the experimental field), in a horse bean plantation. Metagenomic methods (next generation sequencing technology, NGS) were used to determine the percentage of individual operational taxonomic units (OTUs). Our study showed that no-tillage cultivation technologies, mainly strip and no-tillage methods, had a positive effect on microbiological communities. In fact, key species related to soil fertility and crop yield, such as Gemmatimonas aurantiaca (a microorganism that reduce nitrous oxide, N2O in soil) and Aeromicrobium ponti (a beneficial species for the soil environment, essential for the proper functioning of the crop agroecosystem), increased in reduced cultivation technologies. These species can determine soil fertility and crop yields, and therefore, they are very important for sustainable and even regenerative agriculture. Further studies of soil samples collected from other crop plantations under different cropping systems may indicate beneficial microbial species that are important for soil fertility.
Additives Improving the Efficiency of Biogas Production as an Alternative Energy Source—A Review
Additives for anaerobic digestion (AD) can play a significant role in optimising the process by increasing biogas production, stabilising the system and improving digestate quality. The role of additives largely boils down to: (i) enhancing direct interspecies electron transfer (DIET) between microbial communities, resulting in improved syntrophic interactions and methane production rates (e.g. biochar, magnetite and carbon nanotubes), (ii) adsorption of toxic substances that may inhibit microbial activity (e.g. activated carbon, zeolites), (iii) improving microbial activity and increasing process stability (e.g. cobalt, nickel, iron, selenium), (iv) maintaining optimal pH levels for microbial activity (e.g. magnesium oxide), (v) reducing inhibition (the aforementioned adsorbents and conductive substances), (vi) accelerating the decomposition of complex organic materials into simpler compounds that are more easily digested by microorganisms, thereby increasing the rate of hydrolysis (enzymes, including cellulases, proteases and lipases). Through the aforementioned action, additives can significantly affect AD performance. The function of these materials varies, from enhancing microbial activity to maintaining optimal conditions and protecting the system from inhibitors. The choice of additives should be carefully tailored to the specific needs and conditions of the digester to maximise benefits and ensure sustainability. In light of these considerations, this paper characterizes the most commonly used additives and their combinations based on a comprehensive review of recent scientific publications, including a report on the results of conducted studies. The publication features chapters that describe: carbon-based conductive materials, metal oxide nanomaterials, trace metal and biological additives, including enzymes and microorganisms. It concludes with a chapter summarising reports on various additives and discussing their indications for functional systems with determined properties. A notable advantage of this work is the updated literature data, clear summaries, and a substantive description of the performance of the additives discussed.
Fungi of the Trichoderma Genus: Future Perspectives of Benefits in Sustainable Agriculture
The negative impact of chemical pesticides on the environment and human health has contributed to the introduction of legal regulations that ensure the reduction in the use of agrochemicals in favor of biological products. The existing review of the literature, including our research, clearly shows that the ideal biocontrol agents are Trichoderma fungi. The production of antibiotics, lytic enzymes degrading the cell walls of plant pathogens, or inducing a defense response in plants are just some of the features supporting the wide use of these microorganisms in sustainable agriculture. It is estimated that currently about 60% of biofungicides used to eliminate fungal pathogens are produced based on Trichoderma sp. strains.
Wpływ nośników w postaci krzemionki i ligniny na różnorodność mikrobiomu bakteryjnego oraz wydajność fermentacji metanowej
Consortia of Plant Growth-Promoting Rhizobacteria and Selected Catch Crops for Increasing Microbial Activity in Soil under Spring Barley Grown as an Organic Farming System
In order to protect and remediate soils, organic farming methods have grown in popularity. The aim of the study was to evaluate the effect of rhizobacteria (Bacillus subtilis, Bacillus amyloliquefaciens, Pseudomonas fluorescens) and catch crops (undersown red clover alone, undersown Italian ryegrass alone and a mixture of clover and ryegrass) on the microbiological activity of the soil under organic spring barley. In 2019–2021, a field experiment was carried out on an organic farm, randomly in eight variants, each in three repetitions. The following parameters were analyzed: enzymatic activity of dehydrogenases (DHA), acid phosphatase (PAC) and catalase (CAT), soil fertility index (BIF), and a number of selected physiological groups of microorganisms (molds, bacteria, and actinomycetes). Compared to the control variant (without catch crops and bacteria), the values of DHA, CAT, and BIF increased significantly in the variant in which rhizobacteria and catch crops were used simultaneously. The highest BIF, of 32, was obtained in 2019, after the application of red clover catch crop + Italian ryegrass + rhizobacteria. PAC activity dropped significantly after the application of the bacterial consortium alone and was lower than the control by an average of 30%.
Sustainable Methods of Soybean Cultivation in Poland
Many countries in Europe are struggling with a shortage of feed protein; moreover, efforts are being made to limit the import of post-extraction soybean meal, most often from GMO crops. To achieve the above assumptions, varietal progress is necessary and, above all, breeding work should aim at greater adaptation to regional conditions. This study was designed to evaluate the potential for growing Ukrainian soybean ‘Annushka’ in the southeastern Baltic Sea area, in accordance with the application of mineral nitrogen fertilizer and the inoculation of seeds with Bradyrhizobium japonicum. Soybean ‘Annushka’ yielded 0.98–1.68 t ha−1 in the conditions of central Poland. Our experiments have shown significant variations in seed, protein, and fat yields over the years. The maximum amounts of these characteristics were recorded in 2017. Nitrogen fertilization combined with seed inoculation with B. japonicum has proven to be an important factor in improving soybean yields; however, it slightly modified the content of organic compounds in seeds. Improvement in seed and protein yields relative to the control amounted, respectively, to Nitragina + 30 kg N ha−1 (58.8%; 72.6%), HiStick® Soy + 30 kg N ha−1 (57.6%; 68.3%), and Nitroflora + 60 kg N ha−1 (57.6%; 71.9%).
