Unlocking the potential of biofilm-forming plant growth-promoting rhizobacteria for growth and yield enhancement in wheat (Triticum aestivum L.).

Plant growth-promoting rhizobacteria (PGPR) boost crop yields and reduce environmental pressures through biofilm formation in natural climates. Recently, biofilm-based root colonization by these microorganisms has emerged as a promising strategy for agricultural enhancement. The current work aims to characterize biofilm-forming rhizobacteria for wheat growth and yield enhancement. For this, native rhizobacteria were isolated from the wheat rhizosphere and ten isolates were characterized for plant growth promoting traits and biofilm production under axenic conditions. Among these ten isolates, five were identified as potential biofilm-producing PGPR based on in vitro assays for plant growth-promoting traits. These were further evaluated under controlled and field conditions for their impact on wheat growth and yield attributes. Surface-enhanced Raman spectroscopy analysis further indicated that the biochemical composition of the biofilm produced by the selected bacterial strains includes proteins, carbohydrates, lipids, amino acids, and nucleic acids (DNA/RNA). Inoculated plants in growth chamber resulted in larger roots, shoots, and increase in fresh biomass than controls. Similarly, significant increases in plant height (13.3, 16.7%), grain yield (29.6, 17.5%), number of tillers (18.7, 34.8%), nitrogen content (58.8, 48.1%), and phosphorus content (63.0, 51.0%) in grains were observed in both pot and field trials, respectively. The two most promising biofilm-producing isolates were identified through 16 s rRNA partial gene sequencing as Brucella sp. (BF10), Lysinibacillus macroides (BF15). Moreover, leaf pigmentation and relative water contents were significantly increased in all treated plants. Taken together, our results revealed that biofilm forming PGPR can boost crop productivity by enhancing growth and physiological responses and thus aid in sustainable agriculture.

Biodegradation of poly-3-hydroxybutyrate after soil inoculation with microbial consortium: Soil microbiome and plant responses to the changed environment.

Biodegradable plastics play a vital role in addressing global plastics disposal challenges. Poly-3-hydroxybutyrate (P3HB) is a biodegradable bacterial intracellular storage polymer with substantial usage potential in agriculture. Poly-3-hydroxybutyrate and its degradation products are non-toxic; however, previous studies suggest that P3HB biodegradation negatively affects plant growth because the microorganisms compete with plants for nutrients. One possible solution to this issue could be inoculating soil with a consortium of plant growth-promoting and N-fixing microorganisms. To test this hypothesis, we conducted a pot experiment using lettuce (Lactuca sativa L. var. capitata L.) grown in soil amended with two doses (1 % and 5 % w/w) of P3HB and microbial inoculant (MI). We tested five experimental variations: P3HB 1 %, P3HB 1 % + MI, P3HB 5 %, P3HB 5 % + MI, and MI, to assess the impact of added microorganisms on plant growth and P3HB biodegradation. The efficient P3HB degradation, which was directly dependent on the amount of bioplastics added, was coupled with the preferential utilization of P3HB as a carbon (C) source. Due to the increased demand for nutrients in P3HB-amended soil by microbial degraders, respiration and enzyme activities were enhanced. This indicated an increased mineralisation of C as well as nitrogen (N), sulphur (S), and phosphorus (P). Microbial inoculation introduced specific bacterial taxa that further improved degradation efficiency and nutrient turnover (N, S, and P) in P3HB-amended soil. Notably, soil acidification related to P3HB was not the primary factor affecting plant growth inhibition. However, despite plant growth-promoting rhizobacteria and N2-fixing microorganisms originating from MI, plant biomass yield remained limited, suggesting that these microorganisms were not entirely successful in mitigating the growth inhibition caused by P3HB.

Seasonal variation of arsenic in PM10 and PMx in an urban park: The influence of vegetation-related biomethylation on the distribution of its organic species and air quality.

Arsenic (As) levels in particulate matter (PM) are routinely monitored in cities of developed countries. Despite advances in the knowledge of its inorganic species in PM in urban areas, organic species are often overlooked with no information on their behaviour in urban parks - areas with increased potential for As biomethylation. Therefore, the aim of this study was to characterize As distribution, bioaccessibility, seasonal variation and speciation (AsIII, AsV, MMA, DMA and TMAO) in PMx-PM10 of an urban park. Two sites with different distance from the road were selected for winter and summer sampling. From the PM samples, we gravimetrically determined PM10 concentrations in the air and via ICP-MS the total As content there. To assess the portion of bioaccessible As, water extractable As content was analysed. Simultaneously, the As species in PM10 water extracts were analysed via coupling of HPLC with ICP-MS method. There was no seasonal difference in PM10 concentration in the park, probably due to the increased summer PM load related to recreational activities in the park and park design. Spatial distribution of total As in PM10 and As fractional distribution in PMx suggested that As mostly didn't originate from traffic although highest As content was observed in the fine fraction (PM2.5) related to combustion processes. However, significant winter increase of As (determined by AsIII and AsV) despite the unchanged concentration of PM10 indicated a decisive influence of household heating-related combustion and possibly influence of reduced vegetation density. As present in the PM10 was mostly in bioaccessible form. Seasonal influence of As biomethylation was clearly demonstrated on the TMAO specie during the summer campaign. Except the significant summer TMAO increase, the results also indicated the biomethylation influence on DMA. Therefore, an increased risk of exposure to organic As species in urban parks can be expected during summer.

Does poly-3-hydroxybutyrate biodegradation affect the quality of soil organic matter?

The search for eco-friendly substitutes for traditional plastics has led to the production of biodegradable bioplastics. However, concerns have been raised about the impact of bioplastic biodegradation on soil health. Despite these concerns, the potential negative consequences of bioplastics during various stages of biodegradation remain underexplored. Therefore, this study aims to investigate the impact of micro-bioplastics made of poly-3-hydroxybutyrate (P3HB) on the properties of three different soils. In our ten-month experiment, we investigated the impact of poly-3-hydroxybutyrate (P3HB) on Chernozem, Cambisol, and Phaeozem soils. Our study focused on changes in soil organic matter (SOM), microbial activity, and the level of soil carbon and nitrogen. The observed changes indicated an excessive level of biodegradation of SOM after the soils were enriched with micro-particles of P3HB, with concentrations ranging from 0.1% to 3%. The thermogravimetric analysis confirmed the presence of residual P3HB (particularly in the 3% treatment) and underscored the heightened biodegradation of SOM, especially in the more stable SOM fractions. This was notably evident in Phaeozem soils, where even the stable SOM pool was affected. Elemental analysis revealed changes in soil organic carbon content following P3HB degradation, although nitrogen levels remained constant. Enzymatic activity was found to vary with soil type and responded differently across P3HB concentration levels. Our findings confirmed that P3HB acts as a bioavailable carbon source. Its biodegradation stimulates the production of enzymes, which in turn affects various soil elements, indicating complex interactions within the soil ecosystem.

Effect of freeze-thaw manipulation on phytostabilization of industrially contaminated soil with halloysite nanotubes.

The latest trends in improving the performance properties of soils contaminated with potentially toxic elements (PTEs) relate to the possibility of using raw additives, including halloysite nanotubes (HNTs) due to eco-friendliness, and inexpensiveness. Lolium perenne L. was cultivated for 52 days in a greenhouse and then moved to a freezing-thawing chamber for 64 days. HNT addition into PTE-contaminated soil cultivated with grass under freezing-thawing conditions (FTC) was tested to demonstrate PTE immobilization during phytostabilization. The relative yields increased by 47% in HNT-enriched soil in a greenhouse, while under FTC decreased by 17% compared to the adequate greenhouse series. The higher PTE accumulation in roots in HNT presence was evident both in greenhouse and chamber conditions. (Cr/Cd and Cu)-relative contents were reduced in soil HNT-enriched-not-FTC-exposed, while (Cr and Cu) in HNT-enriched-FTC-exposed. PTE-immobilization was discernible by (Cd/Cr/Pb and Zn)-redistribution into the reducible fraction and (Cu/Ni and Zn) into the residual fraction in soil HNT-enriched-not-FTC-exposed. FTC and HNT facilitated transformation to the residual fraction mainly for Pb. Based on PTE-distribution patterns and redistribution indexes, HNT's role in increasing PTE stability in soils not-FTC-exposed is more pronounced than in FTC-exposed compared to the adequate series. Sphingomonas, Acidobacterium, and Mycobacterium appeared in all soils. HNTs mitigated FTC's negative effect on microbial diversity and increased Planctomycetia abundance.

Effect of Mycotoxins in Silage on Biogas Production.

Mycotoxins can pose a threat to biogas production as they can contaminate the feedstock used in biogas production, such as agricultural crops and other organic materials. This research study evaluated the contents of deoxynivalenol (DON), zearalenone (ZEA), fumonisin (FUM), and aflatoxin (AFL) mycotoxins in maize silage prior to it being processed in a biogas plant and in digestate produced at the end of the anaerobic digestion (AD) process. In the experiment, three samples of silage were collected from one silage warehouse: Variant 1 = low contamination, Variant 2 = medium contamination, and Variant 3 = heavy contamination, which were subjected to investigation. A significantly reduced biogas production was recorded that was proportional to the increasing contamination with molds, which was primarily due to the AD of silage caused by technologically erroneous silage treatment. The AD was connected with changes in silage composition expressed by the values of VS content, sugar content, lactic acid content, acetic acid content, and the ratio of lactic acid content to acetic acid content. The production of biogas and methane decreased with the increasing contents of NDF, ADF, CF, and lignin. The only exception was Variant 2, in which the content of ADF, CF, and lignin was lower (by 8-11%) than that in Variant 1, and only the content of NDF was higher (by 9%) than that in Variant 1. A secondary factor that also correlated with changes in the composition of the substrate was the development of undesirable organisms, which further contributed to its degradation and to the production of mycotoxins. It was also demonstrated in this study that during the AD process, the tested mycotoxins were degraded, and their content was reduced by 27-100%. Only the variant with low mold contamination showed a DON concentration increase of 27.8%.

Nickel (Ni) phytotoxicity and detoxification mechanisms: A review.

Scientists studying the environment, physiology, and biology have been particularly interested in nickel (Ni) because of its dual effects (essentiality and toxicity) on terrestrial biota. It has been reported in some studies that without an adequate supply of Ni, plants are unable to finish their life cycle. The safest Ni limit for plants is 1.5 µg g-1, while the limit for soil is between 75 and 150 µg g-1. Ni at lethal levels harms plants by interfering with a variety of physiological functions, including enzyme activity, root development, photosynthesis, and mineral uptake. This review focuses on the occurrence and phytotoxicity of Ni with respect to growth, physiological and biochemical aspects. It also delves into advanced Ni detoxification mechanisms such as cellular modifications, organic acids, and chelation of Ni by plant roots, and emphasizes the role of genes involved in Ni detoxification. The discussion has been carried out on the current state of using soil amendments and plant-microbe interactions to successfully remediate Ni from contaminated sites. This review has identified potential drawbacks and difficulties of various strategies for Ni remediation, discussed the importance of these findings for environmental authorities and decision-makers, and concluded by noting the sustainability concerns and future research needs regarding Ni remediation.

Does biochar in combination with compost effectively promote phytostabilization of heavy metals in soil under different temperature regimes?

The article presents the effect of a combined amendment, i.e., biochar+compost (BC), on the process of Cd, Cu, Ni, Pb and Zn immobilization in soil cultivated with L. perenne under freezing and thawing conditions (FTC). In particular, the speciation analysis of the examined elements in phytostabilized soils based on their response using the sequential extraction, and the variability of the soil microbiome using 16S rRNA gene amplicon sequencing were systematically assessed. Metal stability in soils was evaluated by the reduced distribution index (Ir). Plants were grown in pots for 52 days under greenhouse conditions. After termination, phytostabilization was continued in a temperature chamber for 64 days to provide FTC. As a result, it was noted that biomass yield of L. perenne was promoted by BC (39 % higher than in the control pots) and reduced by FTC (45 % lower than in the BC-enriched soil not exposed to FTC). An efficacious level of phytostabilization, i.e., higher content of heavy metals in plant roots, was found in the BC-enriched soil, regardless of the changes in soil temperature conditions. BC improved soil pH before applying FTC more than after applying FTC. BC had the greatest impact on increasing Cu stability by redistributing it from the F1 and F2 fractions to the F3 and F4 fractions. For most metals, phytostabilization under FTC resulted in an increase in the proportion of the F1 fraction and a decrease in its stability. Only for Pb and Zn, FTC had greater impact on their stability than BC addition. In all soil samples, the core genera with about 2-3 % abundances were Sphingomonas sp. and Mycobacterium sp. FTC favored the growth of Bacteroidetes and Proteobacteria in soil. Microbial taxa that coped well with FTC but only in the absence of BC were Rhodococcus, Alkanindiges sp., Flavobacterium sp., Williamsia sp. Thermomonas sp.

Not so dangerous? PET microplastics toxicity on freshwater microalgae and cyanobacteria.

Microalgae and cyanobacteria are among the most important primary producers and are responsible for the production of 50-80% of the oxygen on Earth. They can be significantly affected by plastic pollution, as the vast majority of plastic waste ends up in rivers and then the oceans. This research focuses on green microalgae Chlorella vulgaris (C. vulgaris), Chlamydomonas reinhardtii (C. reinhardtii), filamentous cyanobacterium Limnospira (Arthrospira) maxima (L.(A.) maxima) and how they are affected by environmentally relevant PET-MPs (polyethylene-terephtalate microplastics). Manufactured PET-MPs have asymmetric shape, size between 3 and 7 µm and were used in concentrations ranging from 5 mg/L to 80 mg/L. The highest inhibitory rate of growth was found in C. reinhardtii (-24%). Concentration-dependent changes in chlorophyll a composition were found in C. vulgaris and C. reinhardtii, not in L. (A.) maxima. Furthermore, cell damage was detected in all three organisms by CRYO-SEM (shriveling, cell wall disruption), but the cyanobacterium was the least damaged. A PET-fingerprint was detected on the surface of all tested organisms using FTIR, indicating the adherence of PET-MPs. The highest rate of PET-MPs adsorption was detected in L. (A.) maxima. Specifically, characteristic spectra were observed at ∼721, 850, 1100, 1275, 1342, and 1715 cm-1 which are specific for functional groups of PET-MPs. Nitrogen and carbon content significantly increased in L. (A.) maxima under exposure to 80 mg/L due to the PET-MPs adherence and mechanical stress. In all three tested organisms, weak exposure-related ROS generation was detected. In general, cyanobacteria seem to be more resistant to the effects of MPs. However, organisms in the aquatic environment are exposed to MPs over a longer time scale, so it is important to use the present findings for further longer-term experiments on environmentally relevant organisms.

The combined effect of graphene oxide and elemental nano-sulfur on soil biological properties and lettuce plant biomass.

The impact of graphene oxide (GO) nanocarbon on soil properties is mixed, with both negative and positive effects. Although it decreases the viability of some microbes, there are few studies on how its single amendment to soil or in combination with nanosized sulfur benefits soil microorganisms and nutrient transformation. Therefore, an eight-week pot experiment was carried out under controlled conditions (growth chamber with artificial light) in soil seeded with lettuce (Lactuca sativa) and amended with GO or nano-sulfur on their own or their several combinations. The following variants were tested: (I) Control, (II) GO, (III) Low nano-S + GO, (IV) High nano-S + GO, (V) Low nano-S, (VI) High nano-S. Results revealed no significant differences in soil pH, dry plant aboveground, and root biomass among all five amended variants and the control group. The greatest positive effect on soil respiration was observed when GO was used alone, and this effect remained significant even when it was combined with high nano-S. Low nano-S plus a GO dose negatively affected some of the soil respiration types: NAG_SIR, Tre_SIR, Ala_SIR, and Arg_SIR. Single GO application was found to enhance arylsulfatase activity, while the combination of high nano-S and GO not only enhanced arylsulfatase but also urease and phosphatase activity in the soil. The elemental nano-S probably counteracted the GO-mediated effect on organic carbon oxidation. We partially proved the hypothesis that GO-enhanced nano-S oxidation increases phosphatase activity.

Time-dependent impact of co-matured manure with elemental sulfur and biochar on the soil agro-ecological properties and plant biomass.

Farmyard manure is the most common type of organic fertilizer, and its properties depend mainly on the type of livestock, bedding material and the conditions of fermentation. Co-maturing of manure with other amendments to modify its final properties has been seen as a win-win strategy recently. This study aimed to evaluate the differences in the effect of unenriched manure and manures co-matured with biochar, elemental sulfur or both amendments on the soil physico-chemical and biological properties, and plant (barley, maize) biomass production. For this purpose a pot experiment was carried out in a time-dependent way. Samples were taken from 12 week-lasting (test crop barley) and 24 week-lasting (test crop maize) pot cultivation carried out in a growth chamber. Co-matured manure with biochar showed the highest rate of maturation expressed as humic to fulvic acid ratio, its amendment to soil significantly increased the dry aboveground biomass weight in the half-time (12 weeks) of experiment. However, the effect vanished after 24 weeks. We received for this variant highest long-term (24 weeks) contents of total carbon and nitrogen in soil. Contrarily, co-matured manure with biochar and elemental sulfur led to short-term carbon sequestration (the highest total carbon in 12 weeks) due to presumed retardation of microbial-mediated transformation of nutrients. We conclude that the prolonged pot experiment with biochar or elemental sulfur enriched manure led to the increased recalcitrancy of soil organic matter and retardation of soil nutrient transformation to the plant-available form.

Effect of Digestate Modified with Amendments on Soil Health and Plant Biomass under Varying Experimental Durations.

A digestate with amendments provides plants with available nutrients and improves the microbiological properties of treated soil. Modification of a digestate through the addition of a biochar and sulphur source is less well-known. This pot experiment aimed at comparing the short- and long-time fertilization effects of a digestate enriched with biochar, with elemental sulphur, or with a combination of both on soil health and plant biomass. The experiment was carried out with maize, cultivated twice (1st-12th week = pre-cultivation; re-sowing after shoot harvest, 13th-24th = main cultivation) in soil amended with prepared digestate. The digestate used in pre-cultivation was incubated untreated (D) and was then treated with biochar (D + B), with elemental sulphur at a low (LS) and high (HS) dose, or with a combination of both (D + B + LS and D + B + HS). An additional unamended digestate (D) was added to each soil variant before the main cultivation. The application of digestate with a high dose of elemental sulphur and biochar mediated the most significant differences in the soil. The increase (compared to the unamended soil) was of short-term type (+11% and +6% increased total nitrogen and carbon after 12 weeks), then of long-term type (+54% and +30% increased sulphur and arylsulfatase activity after 24 weeks), and later emerged in the 13th to the 24th week of the experiment (+57% and +32% non-inhibited urease, increased N-acetyl-ß-D-glucosaminidase and phosphatase). No significant differences in the effect of the applied amendments on dry aboveground plant biomass were observed.

The impacts of mining on soil pollution with metal(loid)s in resource-rich Mongolia.

As Mongolia is considered one of the most resource extraction-dependent countries globally, significant mining-related environmental and human health risks are expected. The aim of this study was to (I) assess the impacts of mining on soil pollution with metals in Mongolia's key coal mining towns (Baganuur, Nalaikh and Sharyn Gol) and (II) review the current knowledge on soil pollution with metal(loid)s and related health risks in Mongolia. The results showed predominantly low soil contents of Cd, Cu, Pb and Zn and a related absence of severe pollution and potential health risk in the coal mining towns. Urban design, rather than the presence of mines, controlled the pollution distribution. Despite the methodological shortcomings of several studies on soil pollution in Mongolia, their results suggest a similarly low threat in the three largest cities (Ulaanbaatar, Darkhan, Erdenet) and several mining areas. While the generally highlighted risk of As seems like an artificially escalated issue, the content of Cr in urban soil may be a neglected threat. Further pollution research in Mongolia should focus on street dust and drinking water pollution.

Possibility of using tannins to control greenhouse gas production during digestate storage.

The presented paper deals with the testing of a possibility to reduce emissions of undesirable greenhouse gases (CH4, CO2; NOx) and their mixture (biogas) during the storage of digestate using applications of secondary plant metabolites (tannins). The experiment was conducted in laboratory conditions in which the digestate was placed in fermentation chambers. Prior to the fermentation process, preparations were applied to the digestate, which contained tannins: Tanenol Antibotrytis (TA), Tanenol Clar (TC) and Tanenol Rouge (TR) in three concentrations (0.5, 1.0 and 2.0% w/w). The application of these preparations demonstrably affected the production of biogas and the contents of CH4, CO2 and N therein. The application of TR preparation in the concentration of 1.0% and 2.0% significantly reduced the production of biogas as compared with all variants. The preparation further inhibited the process of CH4 development. In contrast, the other preparations with the content of different kinds of TA and TC increased the production of biogas (on average by 15%), CH4 (on average by 7%) and CO2 (on average by 12%) as compared with the control variant and TR variant. These two variants reduced the concentration of N in biogas on average by 38%. Thus, the tested Tanenol tannin preparations can be used in different concentrations either to control emissions of greenhouse gases during the storage of digestate or, in case of increased production of CO2 for its reuse in order to increase methane yields in the process of anaerobic fermentation.

Bentonite as a Functional Material Enhancing Phytostabilization of Post-Industrial Contaminated Soils with Heavy Metals.

Growing awareness of the risks posed by pollution of the soil environment is leading to the development of new remediation strategies. The technique of aided phytostabilization, which involves the evaluation of new heavy-metal (HM)-immobilizing amendments, together with appropriately selected plant species, is a challenge for environmental protection and remediation of the soil environment, and seems to be promising. In this study, the suitability of bentonite for the technique of aided phytostabilization of soils contaminated with high HM concentrations was determined, using a mixture of two grass species. The HM contents in the tested plants and in the soil were determined by flame atomic absorption spectrometry. The application of bentonite had a positive effect on the biomass of the tested plants, and resulted in an increase in soil pH. The concentrations of copper, nickel, cadmium, lead and chromium were higher in the roots than in the above-ground parts of the plants, especially when bentonite was applied to the soil. The addition of the analyzed soil additive contributed significantly to a decrease in the levels of zinc, copper, cadmium and nickel in the soil at the end of the experiment. In view of the above, it can be concluded that the use of bentonite in the aided phytostabilization of soils polluted with HMs, is appropriate.

Soil Properties and Maize Yield Improvement with Biochar-Enriched Poultry Litter-Based Fertilizer.

Conversion of poultry litter into fertilizer presents an environmentally friendly way for its disposal. The amendment of stabilizing sorption materials (e.g., biochar) to broiler chicken rearing seems promising, as it protects produced litter from nutrient losses and improves fertilizing efficacy. Thus, a pot experiment was carried out with maize and organic fertilizers produced from biochar-amended chicken bedding. The properties of three types of poultry-matured litter, amended with biochar at 0%, 10% and 20% dose, were analyzed. These matured litters were added to soil and physicochemical, biological properties and dry aboveground crop biomass yield were determined. Both biochar doses improved matured litter dry matter (+29%, +68% compared to unamended litter) and organic carbon (+5%, +9%). All three fertilizers significantly increased dry plant aboveground biomass yield (+3% and +42% compared to control litter-treated variant) and N-acetyl-ß-D-glucosaminidase activity (+51%, +57%) compared to unamended control soil. The 20% biochar poultry-matured litter derived the highest dry plant aboveground biomass, highest respiration induced by D-glucose (+53%) and D-mannose (+35%, compared to control litter-treated variant), and decreased pH (-6% compared to unamended control). Biochar-derived modification of poultry litter maturation process led to organic fertilizer which enhanced degradation of soil organic matter in the subsequently amended soil. Furthermore, this type of fertilizer, compared to conventional unamended litter-based type, increased microbial activity, nutrient availability, and biomass yield of maize in selected biochar doses, even under conditions of significant soil acidification.

Assessment of digestates prepared from maize, legumes, and their mixed culture as soil amendments: Effects on plant biomass and soil properties.

Digestate prepared from anaerobic digestion can be used as a fertilizer, as it contains ample amounts of plant nutrients, mainly nitrogen, phosphorous, and potassium. In this regard, digestates produced from mixed intercropped cereal and legume biomass have the potential to enrich soil and plants with nutrients more efficiently than monoculture-based digestates. The objective of this study was to determine the impact of different types of digestates applied at a rate of 40 t·ha-1 of fresh matter on soil properties and crop yield in a pot experiment with lettuce (Lactuca sativa) as a test crop. Anaerobic digestion of silages was prepared from the following monocultures and mixed cultures: broad bean, maize, maize and broad bean, maize and white sweet clover, and white sweet clover. Anaerobic digestion was performed in an automatic custom-made system and applied to the soil. Results revealed that fresh and dry aboveground biomass as well as the amount of nitrogen in plants significantly increased in all digestate-amended variants in comparison to control. The highest content of soil total nitrogen (+11% compared to the control) and urease (+3% compared to control) were observed for maize digestate amendment. Broad bean digestate mediated the highest oxidizable carbon (+48%), basal respiration (+46%), and N-acetyl-ß-D-glucosamine-, L-alanine-, and L-lysine-induced respiration (+22%, +35%, +22%) compared to control. Moreover, maize and broad bean digestate resulted in the highest values of N-acetyl-ß-D-glucosaminidase and ß -glucosidase (+35% and +39%), and maize and white sweet clover digestate revealed the highest value of arylsulfatase (+32%). The observed differences in results suggest different effects of applied digestates. We thus concluded that legume-containing digestates possibly stimulate microbial activity (as found in increased respiration rates), and might lead to increased nitrogen losses if the more quickly mineralized nitrogen is not taken up by the plants.

Food and agricultural wastes-derived biochars in combination with mineral fertilizer as sustainable soil amendments to enhance soil microbiological activity, nutrient cycling and crop production.

The ever-increasing human population associated with high rate of waste generation may pose serious threats to soil ecosystem. Nevertheless, conversion of agricultural and food wastes to biochar has been shown as a beneficial approach in sustainable soil management. However, our understanding on how integration of biochar obtained from different wastes and mineral fertilizers impact soil microbiological indicators is limited. Therefore, in the present study the effects of agricultural (AB) and food waste derived (FWB) biochars with and without mineral fertilizer (MF) on crop growth and soil health indicators were compared in a pot experiment. In particular, the impacts of applied amendments on soil microbiological health indicators those related to microbial extracellular (C, N and P acquiring) enzymes, soil basal as well as different substrate induced respirations along with crop's agronomic performance were explored. The results showed that compared to the control, the amendment with AB combined with MF enhanced the crop growth as revealed by higher above and below ground biomass accumulation. Moreover, both the biochars (FWB and AB) modified soil chemical properties (pH and electric conductivity) in the presence or absence of MF as compared to control. However, with the sole application of MF was most influential strategy to improve soil basal and arginin-induced respiration as well as most of the soil extracellular enzymes, those related to C, N and P cycling. Use of FWB resulted in enhanced urease activity. This suggested the role of MF and FWB in nutrient cycling and plant nutrition. Thus, integration of biochar and mineral fertilizers is recommended as an efficient and climate smart package for sustainable soil management and crop production.