Plant Residues Research Articles

Characterization of Mixtures of Rugulopteryx okamurae Compost and Plant Residues to Determine the Most Effective Composition as a Substrate and Source of Nutrients

The increasing invasion of Rugulopteryx okamurae algae along the coast of southeastern Spain has prompted efforts to explore its potential as a resource. Consequently, composting this alga is considered a viable solution for agricultural applications. This study investigates the composting process of mixtures of R. okamurae seaweed with plant residues and characterizes the final compost for its use as a substrate and/or source of nutrients to determine the most effective composition of the mixture. The composting process was conducted using varying proportions of seaweed (100%, 30–35%, and 15%) combined with plant residues (from vegetable plants, fruits, and gardens) and included both washed and unwashed seaweed. The first trials revealed challenges associated with Rugulopteryx okamurae, such as a low C/N ratio and algae washing. Consequently, a second trial was conducted to optimize the mixtures, aiming for a C/N ratio close to 30. Additionally, it was decided not to wash the algae to reduce the electrical conductivity (EC) in the mixtures. The findings indicate that the composting process remains unaffected by high electrical conductivity when algae are unwashed. However, washing the algae before composting did affect the compost quality, as the composts with washed algae with garden waste (SwP 34.0 dS m−1) had a lower electrical conductivity (EC) than did the unwashed composts with garden waste (SP 51.6 dS m−1 and SFP 64.9 dS m−1). On the other hand, the compost-only horticultural and garden waste (FHP 43.7 dS m−1) had a high EC; therefore, the EC was not increased with low proportions of unwashed algae, as was seen with the compost with 15% unwashed algae (SFHP 47.6 dS m−1). The other quality parameters were not affected by the absence of algae washing at the beginning of the composting process.

Урожайность масличных культур и пшеницы озимой в зависимости от содержания в чернозёме выщелоченном подвижных форм азота, фосфора и калия в стационарном полевом опыте ВНИИМК

In grain-row crop rotation, sunflower – winter wheat, castor plant – winter wheat, soybean – winter wheat in stationary field experiment in 1981– 1989, we studied contents of nitrate nitrogen, mobile phosphorus, and exchangeable potassium, the degree of phosphate mobility in 0–60 cm layer of leached black soil in the spring after incorporating plant residues of cultivated crops into the soil and applying mineral fertilizers. It was revealed that the application of plant residues and mineral fertilizers in the soil increased the contents of nitrate nitrogen by 0.1–9.0 mg/kg, mobile phosphorus – by 3.7–21.9 mg/100 g, in comparison with the control, depending on culture. On average, according to the experimental variants, the soil received 7.3 t/ha of above-ground plant residues of sunflower, 5.7 t/ha of castor plants, 3.7 t/ha of soybeans, 6.5 t/ha of winter wheat after sunflower, 7.9–8.0 t/ha – after castor plants and soybeans. With plant residues after their mineralization, 42–57 kg/ha of nitrogen, 13– 26 kg/ha of phosphorus, and 30–208 kg/ha of potassium are returned to the soil. The dependence of the yield of sunflower, castor plant, soybean, and winter wheat after oil preceding crops on the contents of nitrate nitrogen, mobile phosphorus, and exchangeable potassium, the degree of phosphate mobility in spring in leached black soil has been established, and regression equations have been calculated. The optimal contents of nitrate nitrogen, mobile phosphorus, and exchangeable potassium, the degree of phosphate mobility in leached black soil in spring for sunflower, castor plants, soybeans, and winter wheat are shown, above which the use of fertilizers for these crops is ineffective. Sunflower, castor plants, and soybeans, as predecessors of winter wheat, have different effects on the dependence of the yield of winter wheat on the content of nitrate nitrogen, mobile phosphorus, and exchangeable potassium in the leached black soil in the spring.

Maximizing resource recovery: Anaerobic digestion of residual biomass from essential oil extraction in four aromatic and medicinal plants

The valorization of organic waste through biomethanization presents a sustainable solution for energy production and waste management. In this study, the objective was to investigate the feasibility of anaerobic digestion for recovering extraction residues from essential oil extraction processes of Lavender, Peppermint, Eucalyptus, and Rosemary. Furthermore, the study aimed to evaluate the characteristics of the residual biomass by determining total organic matter and soluble organic matter using standardized protocols. The digestate obtained after anaerobic digestion was characterized for its physicochemical properties and its potential as an organic amendment. Statistical analysis was conducted to evaluate the results. The results demonstrate variations in these characteristics among different plant residues, with eucalyptus exhibiting lower VMO and higher BOD5 compared to other plants. The results of this study suggest promising potential for energy recovery from extraction residues, with an energy yield of up to 300 kWh/ton of waste. However, fermenting mixtures before anaerobic digestion is not recommended. In addition, the physicochemical characterization of the mixture resulting from the two mixtures MRH and MRF (DB digestate) highlights the potential of the digestate as an organic amendment. It also demonstrates the effectiveness of anaerobic digestion in reducing organic matter and enhancing the quality of the digestate. This contributes to sustainable waste management practices and boosts agricultural productivity. Morphological and elemental analyses provide insight into structural and compositional changes during biomethanization. Overall, this research highlights anaerobic digestion as a cost-effective approach to residual waste disposal in essential oil extraction industries. It supports circular economy principles by potentially generating revenue from energy production and organic amendments. This method offers a promising solution for waste recovery strategies in the transformation sector of aromatic and herbaceous plants for energy production.

Dissipation and residues of imidacloprid in amaranth under greenhouse and open field cultivations

Despite the extensive exposure to imidacloprid residues in food plants, there has been little research on imidacloprid residues in amaranth. The dissipation trend and residue behavior of imidacloprid were evaluated to provide guidelines for imidacloprid application on amaranth under open field and greenhouse. The dissipation rate of imidacloprid in amaranth conformed to the first-order kinetic equation, and the half-lives of imidacloprid in amaranth ranged from 0.29 days in open field to 1.29 days in the greenhouse. After 7 and 14 days from the application of imidacloprid (pesticide dosage, 45 or 67.5 g a.i./ha), the amaranth under the open field and greenhouse growth could be consumed safely with average residues of 0.19 and 0.38 mg/kg, respectively. This result demonstrated that the cultivation has the dominant influence on imidacloprid residue, and the residue of imidacloprid in amaranth planting on open field was much lower than that in the greenhouse, indicating a significant difference in the pesticide residues between the two cultivations with a p-value less than 0.05.

Influence of biodestructors on sequestration of labile carbon compounds in the soil

Ukraine stands as a testament to agricultural wealth due to its fertile soils, most notably, its significant share of the world’s chornozem. Rich soil is fundemantal to agricultural production, and therefore the success of the agricultural industry heavily relies on the fertility of the soil. However, modern agricultural practices in Ukraine, have led to increased anthropogenic impact on soils, affecting their biodiversity and humus content. In this regard, it is becoming increasingly important to perform comprehensive studies of microbiological, biochemical and chemical processes in the soil in response to different agricultural interventions. The urgent need to restore natural ecosystems to preserve their biodiversity and ensure ecological stability poses new scientific challenges, emphasizing the importance of urgent measures aimed at protecting the environment from pollution and degradation. This research aims to explore the effects of biodestructors on the deposition of labile carbon compounds in the soil during long-term consistent corn cultivation. The research was conducted during 2020–2023 within the framework of a stationary field experiment of the scientific research department of the «Druzhba Nova» in Varva village, Chernihiv region. The soil is a typical low-humus chornozem with the experiment focusing on a monoculture corn crop rotation. The DKC 4351 corn hybrid was sown at a density of 82 thousand units per hectare, employing a three-part experiment design: 1) a UAN control at 32–28 l/ha, 2) Ecostern Classic at 2 l/ha combined with UAN 32–28 l/ha, and 3) Ecostern Bacterial at 2 l/ha alongside Ecostern Trichoderma at 1 l/ha and UAN 32–28 l/ha. In the present study, the influence of biodestructors on soil’s agrochemical and microbiological indicators, as well as corn yield was evaluated. In a long-term stationary field experiment conducted on a typical low-humus chornozem, we investigated the influence of microbial preparations — plant residue biodestructors — on the deposition of labile carbon compounds in the soil under continuos corn cultivation. The application of Ecostern Classic and a combination of Ecostern Bacterial + Ecostern Trichoderma biodestructors resulted in an increase of labile carbon content by 0.11% and 0.18%, respectively, compared to the control. The aim of further analysis was to determinate the dynamics of the organic matter transformation coefficient, which is a marker of enhanced microbiological activity in the soil and a predominance of organic matter synthesis over its mineralization. In treatments utilizing biodestructors, this indicator was significantly higher than control values throughout the study. The survival of the fungal bioagent from Ecostern Classic and Ecostern Trichoderma bioproducts in the soil was monitored by assessing the population dynamics of the Trichoderma genus species. Results demonstrated an increase by an average of 19 thousand CFU/g with Ecostern Classic and by 34 thousand CFU/g with the combined use of Ecostern Bacterial with Ecostern Trichoderma, compared to 28 thousand CFU/g in control soil samples. This may indirectly indicate a successful colonization of the bioagent in treated soils. Using BIOTREX technology to evaluate the soil’s ecophysiological diversity, we found that the diversity index increased from 3.66 in control samples to between 4.87 and 5.61 in treatments with biodestructors. According to the further BIOTREX assessment, the use of biodestructors not only increased soil biodiversity, but also improved soil health. The application of these biodestructors also significantly boosted corn grain yield with an increase of 0.32 t/ha with Ecostern Classic treatment and 0.18 t/ha with the combined use of Ecostern Bacterial with Ecostern Trichoderma, compared to control.

Assessment of products of anaerobic fermentation of organic raw material from poultry last by microbiological indicators

The product of anaerobic microbiological transformation of bird droppings is a liquid suspended product (digestate), the composition of which is characterized by new chemical features acquired due to the activity of anaerobic microorganisms. This process takes place in biogas plants, and as a result of methane fermentation of bird droppings, biogas and residues of organic raw materials are formed, which are used as fertilizer. The international practice of using digestate as an organic fertilizer or soil improver for the farm’s own needs is similar to classic composts and does not require sanitary and microbiological certification, but there are voluntary certification standards, as well as various industry guidelines on the quality of organic fertilizers. The work analyzes international and national sanitary microbiological standards regarding digestates, products of processing by-products of animal husbandry and organic substances for application to the soil, in particular Regulation (EU) 2019/1009 of the European Parliament and the Council of June 5, 2019 «On establishing rules for placing fertilizers on the market EU», DSTU 7527:2014 «Poultry droppings. Technologies of biological processing. General requirements», DSTU 7938:2015 «Organic fertilizers. Agronomic requirements for the quality of fertilizers for use in organic production». Information from scientific articles, standards of individual countries and guidelines of international voluntary certification bodies regarding the assessment of digestate applied to the soil as an organic fertilizer or soil improver is summarized. It has been established that mandatory sanitary microbiological characteristics for such substances are Salmonella bacteria (Salmonellas spp.) and Escherichia spp. bacteria, as well as the standards of some countries and scientific literature recommend determining Coliform bacteria and Streptococ-cus faecalis bacteria, the presence of which indicates the possible presence of potentially dangerous strains of microorganisms. With the use of laboratory equipment, the granulation conditions of the solid fraction of the digestate were optimized to obtain granulated organic fertilizer from the sludge of the biogas plant. A microbiological analysis of granulated digestate from a biogas plant on bird droppings was carried out in order to establish its compliance with the sanitarybacteriological requirements for organic fertilizers. The presence of pathogens of infectious diseases in poultry droppings and the presence of phytopathogens in grain, which is used for the preparation of premixes, increases their probable migration into the composition of organic fertilizer in case of improper methane fermentation with violation of temperature and exposure conditions. Microbiological analysis of granulated digestate showed the absence of Salmonellas spp. and Escherichia spp. bacteria in the studied samples, but a high number of mold fungi 1.2·104±7.25·102 CFU/g was found, which may be a consequence of storage wet raw materials. In order to prevent microbiological contamination during the storage and transportation of raw materials and organic fertilizers, a necessary condition is compliance with sanitary requirements for all technological processes, starting from the conditions of keeping and feeding animals to the conditions of storage of finished products and application to the soil. The content of harmful microorganisms in the digestate of biogas plants operating on bird droppings or animal manure without litter or the addition of plant residues and chemicals depends mainly on the quality of the droppings and water. The quality of raw materials affects the quality of the digestate and is determined by the sanitary-epidemiological condition of animals and premises, microbiological contamination of feed, pre-treatment of raw materials for loading to the biogas plant. It was established that the granular digestate from bird droppings meets the requirements of Ukrainian standards DSTU 7527:2014 regarding organic fertilizers from poultry droppings and DSTU 7938:2015 regarding organic farming, which allows for further substantiation of optimal application technologies. To control the secondary bacterial contamination of organic raw materials during the storage process, the effectiveness of the use of commercial biological preparations was evaluated. The perspective of using commercial microbial preparations, in particular MycoHelp, to control mold fungi of the genus Penicillum spp. in the technologies of processing by-products of agriculture into organic fertilizers and preventing spoilage of finished products during storage.

Construction of a physiologically based pharmacokinetic model of paclobutrazol and exposure estimation in the human body

Paclobutrazol (PBZ) is a plant growth regulator that can delay plant growth and improve plant resistance and yield. Although it has been widely used in the growth of medicinal plants, human beings may take it by taking traditional Chinese medicine. There are no published studies on PBZ exposure in humans or standardized limits for PBZ in medicinal plants. We measured the solubility, oil–water partition coefficient (logP), and pharmacokinetics of PBZ in rats and established a physiologically based pharmacokinetic (PBPK) model of PBZ in rats. This was followed by extrapolation to healthy Chinese adult males as a theoretical foundation for future risk assessment of PBZ. The results showed that PBZ had low solubility and high fat solubility. Pharmacokinetic experiments showed that PBZ was absorbed rapidly but eliminated slowly in rats. On this basis, the rat PBPK model was successfully constructed and extrapolated to healthy Chinese adult males to predict the plasma concentration–time curve and exposure of PBZ in humans. The construction of the PBPK model of PBZ in this study facilitates the determination of the standard formulation limits and risk assessment of PBZ residues in medicinal plants.

Soil fertility and accumulation of biophilic elements in plant residues of sweet sorghum

Soil fertility and accumulation of biophilic elements in plant residues of sweet sorghum

Low Carbon Loss from Long-Term Manure-Applied Soil during Abrupt Warming Is Realized through Soil and Microbiome Interplay.

Manure application is a global approach for enhancing soil organic carbon (SOC) sequestration. However, the response of SOC decomposition in manure-applied soil to abrupt warming, often occurring during diurnal temperature fluctuations, remains poorly understood. We examined the effects of long-term (23 years) continuous application of manure on SOC chemical composition, soil respiration, and microbial communities under temperature shifts (15 vs 25 °C) in the presence of plant residues. Compared to soil without fertilizer, manure application reduced SOC recalcitrance indexes (i.e., aliphaticity and aromaticity) by 17.45 and 21.77%, and also reduced temperature sensitivity (Q10) of native SOC decomposition, plant residue decomposition, and priming effect by 12.98, 15.98, and 52.83%, respectively. The relative abundances of warm-stimulated chemoheterotrophic bacteria and fungi were lower in the manure-applied soil, whereas those of chemoautotrophic Thaumarchaeota were higher. In addition, the microbial network of the manure-applied soil was more interconnected, with more negative connections with the warm-stimulated taxa than soils without fertilizer or with chemical fertilizer applied. In conclusion, our study demonstrated that the reduced loss of SOC to abrupt warming by manure application arises from C chemistry modification, less warm-stimulated microorganisms, a more complex microbial community, and the higher CO2 intercepting capability by Thaumarchaeota.

Method of corn contamination decreasing after later harvesting predecessors under energy-storage soil maintenance system in irrigation landscapes

The research was carried out at Agrofirm Chokh of the Gunibsky district in the Kizilyurt transhumance zone of the Republic of Dagestan on light chestnut soil. The humus content in the arable layer is 2.77%, P2O5 – 2.21, K2O – 32.8 mg/100 g of soil, the density of the arable layer is 1.24 g/cm3, the lowest moisture capacity (MC) of the soil layer 0–0.6 m is 29.2%. We studied the influence of two corn predecessors: sunflower and corn itself during the main tillage for corn based on plowing to a depth of 28–30 cm without skimmers and with skimmers. During the autumn period, after harvesting the predecessors, the soil was not cultivated, and in the spring, upon the onset of its physical ripeness, two treatments were carried out in a layer of 0–15 cm with disk cultivators to crush the plant residues of the previous crop and plowing to 28–30 cm with a PLN-4-35 plow when physical ripeness of the soil in this layer. It has been established that a radical way to reduce the weediness of corn crops and increase its yield in the irrigated conditions of the Western Caspian region when placed after late-harvested predecessors, including repeated sowings in the same field, is to carry out basic tillage and moisture-recharging irrigation in the spring of the year of sowing. To chop the plant mass remaining after harvesting the predecessor, double processing with disc implements should be carried out before plowing. Plowing is carried out with skimmers, which ensure uniform distribution of weed seeds in the surface layer and their simultaneous germination at a later date than when plowing without skimmers. Subsequently, their life activity is limited to vegetative corn plants. The infestation of corn crops with such soil treatment is reduced three times, the corn yield for the predecessor corn increases by 1.12 t/ha of grain (16.3%), after sunflower – 1.32 t/ha (17.8%).

Characterization and evaluation of actinomycete from the Protaetia brevitarsis Larva Frass.

Protaetia brevitarsis larvae (PBL) are soil insects important for the soil organic carbon cycle, and PBL frass not only contains a large amount of humic acid but also affects the diversity, novelty, and potential functions of actinomycetes. Here, we characterized and assessed the actinomycete. The operational taxonomic unit (OTU) data showed that 90% of the actinomycetes cannot be annotated to species, and pure culture and genome analysis showed that 35% of the strains had the potential to be new species, indicating the novelty of PBL frass actinomycetes. Additionally, genome annotation showed that many gene clusters related to antifungal, antibacterial and insecticidal compound synthesis were identified, and confrontation culture confirmed the antifungal activities of the actinomycetes against soil-borne plant pathogenic fungi. The incubation experiment results showed that all isolates were able to thrive on media composed of straw powder and alkaline lignin. These results indicated that PBL hindgut-enriched actinomycetes could survive in soil by using the residual lignocellulose organic matter from plant residues, and the antibiotics produced not only give them a competitive advantage among soil microflora but also have a certain inhibitory effect on plant diseases and pests. This study suggests that the application of PBL frass can not only supplement soil humic acid but also potentially affect the soil microbiota of cultivated land, which is beneficial for the healthy growth of crops.

Impact of using cover crop on predation slug on corn in Pennsylvania

Farmers in Pennsylvania face a significant obstacle in the form of slug insect management. Aims of this study to determine impact of using cover crop against slug attacks in Pennsylvania. This study collaborated with a Pennsylvania regional no-till farming unit to assign three treatments to each farmer: no crop cover (CA), plastic mulch cover (CP), green rye cereal cover (CRH), and dry rye cereal cover (CRK). The experiment was carried out in May – August in 2023. The use of rye cereal cover crops, both in green and dry form, can also have the potential to reduce slug pests. These plants provide shelter and breeding ground for natural enemies of slugs. Plant residue mulching in conservation farming practices provide an effective and sustainable slug pest management strategy. The use of rye cereal can be a reference for farmers in anticipating slug pests in an environmentally friendly manner.

Results of the Paleobotanical Researches at the Territory of the Nakhchivan Autonomous Republic of Azerbaijan

The article indicates the results of paleobotanical research in the territory of the Nakhchivan Autonomous Republic of Azerbaijan. Materials for fossil plants in the territory Nakhchivan Autonomous Republic show that the development of the Mesophytic era covers the Permian, Triassic, Jurassic, Cretaceous, during which existed Neomesophyte and Palaeomesophyte flora. Сenophytic era covers Paleogene, Neogene and Quaternary period. Flora of Nakhchivan Autonomous Republic relates to Mesophytic and Сenophytic era. Modern vegetation of the region is dominated by open and semi-open coenosis i.e. rather primitive in its phytocenotic essence. These xerophilous coenosis have deep ancient roots of its origin. Flowering flora originated on the globe in the first half of the Cretaceous period. The oldest plant residues, which are known in Nakhchivan Autonomous Republic, refer to the end of the Cretaceous period. Found that modern flora and vegetation of their origin, above all, connected with the ancient Iranian, mainly Asia Minor or North Iranian flora penetrated here with Tertiary and being penetrated at the moment. From the more important temperate eastern slopes of the Lesser Caucasus in the Tertiary period, the study area was fenced off by the high perched Kongur-Alangez mountains and Zangezur.

Influence of cultivation methods on the soil aggregate state in the context of weed development in winter wheat plantations

Weed control in winter wheat crops is an important issue. There is a risk of increasing populations of certain weed species that are resistant to some of herbicides used for winter wheat crops. This could be controlled by a combination of agronomic, mechanical, chemical, and biological methods. After introducing winter wheat into the rotation and improving tillage, the weediness of regular black soils with perennial root and emerged weeds were significantly reduced. The formation of nodal and rudimentary roots had a significant effect on the productivity of winter wheat under different soil moisture conditions. The highest yield of winter wheat was obtained when sown at the optimum time, with higher stem density and ear productivity due to better grain fullness. We studied what effects did the tillage methods have on the aggregate state of the soil in relation to weed development in winter wheat crops, finding that the structural and aggregate composition of the soil played an important role in winter wheat crops, influencing both the development of the crop root system and the water-physical balance of the chernozem, as well as naturally influencing the course of erosion processes in the experimental plots, and having a universal dynamic in terms of adaptation of aggregation and disaggregation processes. Prolonged mechanical stress on soil can cause destruction of its structure. For instance, continuous ploughing or moldboardless tillage with little or no manure application may permanently reduce soil fertility by increasing humus mineralisation. Subsequently, these factors may cause a significant decline in the soil's structural and aggregate composition, resulting in larger amounts of dusty particles smaller than 0.25 mm and cloddy particles larger than 10–12 mm. The soil's structural condition before sowing winter wheat in early September, on average for 2011–2016, indicates increased dispersion of the tilth layer (0–10 cm) in the experimental variants where shallow disc tillage of 10–12 cm was applied. Increase in the number of clods larger than 10 mm in the areas where moldboardless tillage had been applied can be attributed to significant soil drainage. The soil's aggregate state was rated as good, with 8.7% in the 0–10 cm soil layer and 1.7% of clods > 10 mm in the 0–30 cm layer. In 2014–2016, it was rated as satisfactory, with 7.4% and 9.8% of clods > 10 mm, respectively. Shallow disc cultivation resulted in slightly worse indicators: 6.6% and 8.3% of clods > 10 mm in soil layer 0–10 cm and 0–30 cm, respectively, in 2011–2013; and 7.2% and 6.9% of clods > 10 mm, respectively, in 2014–2016. In general, the parameters of optimal structural condition were positive. The tillage method used had a considerable effect on weed growth and development, particularly for those with a root and rhizome structure. It also affected the prevalence and development of pests and diseases in winter wheat. Agrotechnical methods of weed control do not guarantee complete destruction of weeds. Mechanical moldboardless tillage to the depth of 14–16 cm and disc tillage to the depth of 10–12 cm left the fields with 4.1 to 8.8 annual weeds per square meter and 1.3 to 3.3 specimens of harmful root weeds such as Convolvulus arvensis, Lactuca tatarica and Cirsium arvense. Mechanical moldboardless tillage to the depth of 14–16 cm and disc tillage to the depth of 10–12 cm left the fields with 4.1 to 8.8 annual weeds per square meter and 1.3 to 3.3 specimens of harmful root weeds such as Convolvulus arvensis, Lactuca tatarica and Cirsium arvense. Post-harvest residues (4–5 t/ha) can provide almost complete protection against weeds by covering the soil surface. However, pests and diseases may spread more easily due to preservation of fungal spores on the surface of plant residues and preservation of pest larvae in the straw and soil. The distribution of weed seeds in the soil was altered when the rotational tillage of common chernozems in winter wheat cultivation technology had been replaced with energy–saving minimum tillage (shallow flat-cutting disc tillage). This resulted in the concentration of most of the weed seeds (85–90%) in the upper soil layer (0–10 cm).

Molecular Composition of Humic Acids of Different Aged Fallow Lands and Soils of Different Types of Use in Northwest of Russia

Post-agrogenic transformation of fallow soils leads to changes in soil carbon content, the molecular composition of humic substances, and rates of organic matter stabilization, which can affect climate change on the planet. In this regard, we analyzed the molecular composition of humic acids isolated from natural and fallow soils in the southern Taiga zone of northwest Russia. Different-aged soils on fallow lands represent a model of soil transformation in time, and data on the transformation of soil humic acid molecular composition make a significant contribution to the understanding of soil organic matter stabilization aspect issues. In this case, the molecular structure of humic acids isolated from natural and fallow soils in northwest Russia was analyzed. To study the molecular composition of HAs, the elemental composition was analyzed, and 13C (CP/MAS) NMR spectroscopy of HAs isolated from different aged abandoned soils and soils of different types of use was carried out. The obtained data showed that with the increasing age of soils in the fallow state, there is an increase in the carbon content of humic acids as well as a decrease in nitrogen content. As a result of the increasing age of soils in the fallow state, there are dynamics in the content of aromatic structural fragments in humic acids: 34% for 40 years old, 28% for 80 years old, and 31% for 120 years old. This is due to changes in the precursors of humification and the further transformation of plant residues in the soil. Re-involved fallow land soils lead to an increase in the content of aromatic structural fragments in the composition of HA in relation to HA extracted from mature soils. The lowest content of aromatic structural fragments was observed in the humic acids of 130-year-old agricultural soil, which is associated with the long-term application of organic fertilizers.

Reduced belowground allocation of freshly assimilated C contributes to negative plant-soil feedback in successive winter wheat rotations

Abstract Aims Successive winter wheat (WW) rotations are associated with yield reduction, often attributed to the unfavorable soil microbes that persist in the soil through plant residues. How rotational positions of WW affect the allocation of freshly assimilated carbon (C), an energy source for soil microbes, above and belowground remains largely unknown. Methods A 13CO2 pulse labeling rhizotron experiment was conducted in the greenhouse to study freshly fixed C allocation patterns. WW was grown in soil after oilseed rape (W1), after one season of WW (W2), and after three successive seasons of WW (W4). We used an automatic manifold system to measure excess 13C of soil respiration at six depths and five different dates. Excess 13C was also measured in dissolved organic C (DOC), microbial and plant biomass pools. Results There was a strong yield decline in successive WW rotations accompanied by distinct changes in root growth. Higher excess 13C of soil respiration was measured in W1 compared to W4, especially in the topsoil during at later growth stages. Higher excess 13C of the DOC and the microbial biomass was also traced in W1 and W4 compared to W2. Less 13C was taken up by successive WW rotations. Conclusions Our study demonstrates a mechanism through which the rotational position of WW affects the allocation of freshly assimilated C above and belowground. WW after oilseed rape sustains belowground allocation of freshly assimilated C for a longer time than successively grown WW and incorporates more of this C to its biomass.

Straw from Different Crop Species Recruits Different Communities of Lignocellulose-Degrading Microorganisms in Black Soil.

The biological degradation of plant residues in the soil or on the soil surface is an integral part of the natural life cycle of annual plants and does not have adverse effects on the environment. Crop straw is characterized by a complex structure and exhibits stability and resistance to rapid microbial decomposition. In this study, we conducted a microcosm experiment to investigate the dynamic succession of the soil microbial community and the functional characteristics associated with lignocellulose-degrading pathways. Additionally, we aimed to identify lignocellulose-degrading microorganisms from the straw of three crop species prevalent in Northeast China: soybean (Glycine max Merr.), rice (Oryza sativa L.), and maize (Zea mays L.). Our findings revealed that both the type of straw and the degradation time influenced the bacterial and fungal community structure and composition. Metagenome sequencing results demonstrated that during degradation, different straw types assembled carbohydrate-active enzymes (CAZymes) and KEGG pathways in distinct manners, contributing to lignocellulose and hemicellulose degradation. Furthermore, isolation of lignocellulose-degrading microbes yielded 59 bacterial and 14 fungal strains contributing to straw degradation, with fungi generally exhibiting superior lignocellulose-degrading enzyme production compared to bacteria. Experiments were conducted to assess the potential synergistic effects of synthetic microbial communities (SynComs) comprising both fungi and bacteria. These SynComs resulted in a straw weight loss of 42% at 15 days post-inoculation, representing a 22% increase compared to conditions without any SynComs. In summary, our study provides novel ecological insights into crop straw degradation by microbes.

Effects of sustainable agricultural practices on soil microbial diversity, composition, and functions

Soil microorganisms can provide multiple benefits to agroecosystems, which are assumed to be promoted by sustainable agricultural practices. However, the mechanisms that explain this relationship have not been clearly elucidated. Although studies have reported that sustainable agricultural practices promote microbial biomass, the broader implications for soil microbial composition and functions remain uncertain. Accordingly, we searched field experiments worldwide contrasting soil microbial communities under conventional and sustainable agricultural practices. We analysed 924 results of relative abundance of bacteria or fungi (using 16 S and ITS rRNA amplicon sequencing, respectively) at the Family taxonomic level obtained from 46 articles. We found higher soil bacterial richness and higher abundance of copiotrophic bacteria under sustainable agricultural practices. Organic fertilisation promoted the abundance of bacteria involved in C and N cycling, while conservation tillage decreased those involved in the decomposition of plant residue. While sustainable agricultural practices had a minor effect on the overall fungal structure, they led to increases in symbiotic fungi abundance (e.g., Geoglossaceae). Additionally, we observed a slight increase in arbuscular mycorrhizal fungi and a slight reduction in pathogenic fungi associated with plant disease (e.g., Botryosphaeriaceae). Higher soil microbial taxonomic diversity did not lead to increased soil multifunctionality; however, it could safeguard resilience for soil functions via the diversity insurance effect. This study establishes that sustainable agricultural practices can significantly influence microbial communities, leading to compositional and structural changes, as well as promoting relevant functions for agroecosystems. Altogether, these results highlight the importance of integrating concepts of community ecology into agricultural management practices for reaching sustainable agricultural systems.

Carbon slow-release and enhanced nitrogen removal performance of plant residue-based composite filler and ecological mechanisms in constructed wetland application

Stable carbon release and coupled microbial efficacy of external carbon source solid fillers are the keys to enhanced nitrogen removal in constructed wetlands. The constructed wetland plant residue Acorus calamus was cross-linked with poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) to create composite solid carbon source fillers (Ac-BDPs). The study demonstrated the slow release of carbon sources from Ac-BDPs with 35.27 mg/g under an average release rate of 0.88 mg/(g·d). Excellent denitrification was also observed in constructed wetlands with Ac-BDPs. Moreover, the average removal rate of nitrate nitrogen (NO3−-N) was increased by 1.94 and 3.85 times of the blank groups under initial NO3−-N inputs of 5 and 15 mg/L, respectively. Furthermore, the relatively high abundances of nap, narG, nirKS, norB, qnorZ and nosZ guaranteed efficient denitrification performance in constructed wetlands with Ac-BDPs. The study introduced a reliable technique for biological nitrogen removal by using composite carbon source fillers in constructed wetlands.

Composting and fermentation: mitigating hop latent viroid infection risk in hop residues

Hop cultivation, integral to the brewing industry, faces challenges from viroids, especially the citrus bark cracking viroid (CBCVd) but also the hop latent viroid (HLVd) influences hop cone quality. We focused on the degradation kinetics of HLVd thereby covering compost, silage, and digestate made from hop residues. In this study, HLVd serves as a model for understanding CBCVd, which causes significant stunting and yield losses in European hop crops. Composting experiments revealed that although composting significantly lowers HLVd levels, complete degradation within 7 weeks is not guaranteed, with loose compost showing a more rapid reduction than compacted variants. Infectivity experiments conducted using inocula obtained from HLVd-infected hop plant residues exposed to composting, ensiling, and biogas digestate did not result in the transmission of HLVd to viroid-free plants. Also extracting and analyzing the soil-root mixture of plants inoculated with HLVd-infected hop residues did not show evidence for viroid persistence. Degradation experiments further differentiated between the physiochemical and biological influences on viroid and viroid-like random RNA stability, showing that higher temperatures of 50 °C enhance degradation over 40 °C, and pH levels of 5 or 7 are slowing degradation. In contrast deionized water or a pH of 4 or 9 enhances viroid degradation. Adding extracts from digestate accelerated the process indicating a role of biological activity. Interestingly, a viroid-like random RNA with similar physiochemical properties, showed to degrade faster compared to HLVd, suggesting high robustness of the actual viroid secondary structure. These findings offer valuable insights into managing HLVd in hops and potentially other crops, highlighting effective strategies to mitigate viroid spread, and contributing to broader understanding of RNA degradation in agriculture.