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The effects of biochar application on dry direct-seeded rice paddies remains unclear. Therefore, we applied biochar to dry direct-seeded rice paddy fields over 3 consecutive years to assess its effects on soil physicochemical properties and bacterial diversity (conventional fertilization [CK]; biochar + conventional fertilization [BC]). BC increased the content of 0.25–5 mm soil water-stable aggregate particles, but decreased that of <0.25 mm soil water-stable aggregates. At different soil depths, BC significantly reduced sand content and increased silt content. Compared to CK, BC significantly increased the available phosphorus and potassium content of the 0–10 and 10–20 cm soil layers. There were no significant differences in pH, organic matter, total nitrogen, total phosphorus, or total potassium content between the treatments at different soil depths. Compared to CK, BC significantly increased soil neutral phosphatase and catalase activities. Furthermore, BC significantly increased bacterial richness, but had no significant effect on bacterial diversity. According to Qualcomm sequencing analysis, BC increased the relative abundance of Verrucomicrobia, Chloroflexi, Bacteroidetes, Nitrospirae, Verrucomicrobiae, Blastocatellia_Subgroup_4, and Anaerolineae in soil compared to CK. The soil bacterial genera in BC had stronger interrelationships than those in CK. According to redundancy analysis, organic matter was the main environmental factor influencing bacterial community structure. Overall, biochar could promote soil nutrient conversion in dry direct-seeded rice paddies, improve soil effective nutrient content, change the composition of soil bacterial communities, and increase soil bacterial richness. Applying biochar in dry direct-seeded rice cultivation could help realize low-carbon agriculture. [ABSTRACT FROM AUTHOR]

Salt stress and nutrient deficiency strongly limited the productivity of coastal saline-alkali land in the Yellow River Delta. Biochar has been widely used to improve soil health and promote crop yield, and the positive effects of nitrification inhibitors on fertilizer use efficiency, especially nitrogen, were also verified. However, there were few types of research on the combined application of biochar and nitrification inhibitor dicyandiamide (DCD) on saline-alkali soil of the Yellow River Delta, China. In this study, five treatments, including no nitrogen (CK), normal NPK (N), NPK + 1%biochar (B), NPK + 2%DCD (D), and NPK + 1%biochar + 2%DCD (BD) were set to investigate the single and combined effect of biochar and DCD on nitrogen transform, soil properties, bacterial community structure, and soybean production. Results showed that BD application inhibited nitrification and increased the soil's nitrate supply at the flowering stage, which reduced nitrogen waste and met the nitrogen demand for soybean growth. Biochar addition increased the soil's pH and decreased the soil's electrical conductivities and accelerated the soil's macroaggregates formation, with the soil's average mass diameter and geometric average diameter increasing by 78.69% and 30% in B, and 71.29% and 29.34% in BD relative to CK. Positive effects of inhibitors on soybean production were found in increasing soybean yield, hundred-grain weight, aboveground biomass, etc. Proteobacteria was the dominant phylum in the bacterial communities detected, and bacterial community diversity was significantly explained by nitrate content and soil aggregates (p < 0.05). Soil pH and DCD addition mainly influenced the abundance of the bacterial community, especially Actinobacteria. Biochar with DCD could be a feasible fertilization scheme for the coastal saline-alkali land in the Yellow River Delta, China. [ABSTRACT FROM AUTHOR]

It is important to explore efficient materials to alleviate the negative effect of atrazine in soils or water. In this paper, four Fe/Mn-modified biochars were prepared to enhance atrazine removal. The batch adsorption experiment was conducted to explore the adsorption ability of biochar(DBC) and modified biochars (F3M1DBC, F1M3DBC, MnDBC, and FeDBC) on atrazine, and the adsorption mechanism was conducted by XRD, XPS, and FTIR. The modified biochar showed larger specific surface areas and zero-point charge than those of the original biochar. The increased oxygen functional groups (OH, C=C, and C=O) and the formation of Fe3O4, Mn3O4, and FeMnO3 on modified biochar improved atrazine removal. The maximum atrazine adsorption by F3M1DBC was 4.3 times higher than that of DBC. The atrazine adsorption by modified biochar was not pH-dependent, and their removal of atrazine was dominated by adsorption rather than degradation. The desorption rate was 8.61% for F3M1DBC, 15.95% for F1M3DBC, 26.19% for MnDBC, and 29.83% for FeDBC, which were 29.1–79.5% lower than that of DBC, accordingly decreased the environmental risk. XPS and FTIR analysis proved that the adsorption mechanisms of Fe/Mn-modified biochars were mainly attributed to their strong π–π interactions between atrazine and oxygen functional groups, graphitic carbon, and Fe/Mn-oxides on the surface of biochar. In addition, the larger surface area and pore structure of modified biochar contributed to the adsorption and pore filling of atrazine on biochar. In general, the Fe/Mn-modified biochars can be used as effective adsorbents to remove atrazine from soils and waters. [ABSTRACT FROM AUTHOR]

The incorporation of biochar into soils has been recognized as a promising method to combat climate change. However, the full carbon reduction potential of biochar in paddy soils is still unclear. To give an overview of the quantified carbon reduction, a meta-analysis model of different carbon emission factors was established, and the life cycle-based carbon reduction of biochar was estimated. After one year of incorporation, biochar significantly increased the total soil carbon (by 27.2%) and rice production (by 11.3%); stimulated methane (CH4) and carbon dioxide (CO2) emissions by 13.6% and 1.41%, respectively, but having insignificant differences with no biochar amendment; and reduced nitrous oxide (N2O) emissions by 25.1%. The soil total carbon increase was mainly related to the biochar rate, whereas CH4 emissions were related to the nitrogen fertilizer application rate. Biochar pyrolysis temperature, soil type, and climate were the main factors to influence the rice yield. The total carbon reduction potential of biochar incorporation in Chinese paddy soils in 2020 ranged from 0.0066 to 2.0 Pg C using a biochar incorporation rate from 2 to 40 t ha−1. This study suggests that biochar application has high potential to reduce carbon emissions, thereby contributing to the carbon neutrality goal, but needs field-scale long-term trials to validate the predictions. [ABSTRACT FROM AUTHOR]

Excessive application of nitrogen (N) fertilizer will cause many adverse consequences in paddy fields, especially for the reduction in N use efficiency. Biochar can be used to replace part of N fertilizer for rice production. A field experiment of 2-year/four-season was conducted to investigate the effects of N fertilizer reduction combined with rice straw biochar application on rice yield, soil fertility, and N use efficiency. The experiment contained six treatments: No N application (CK), customary N application (N100), 20% N reduction (N80), 20% N reduction + biochar (N80+BC), 40% N reduction (N60), and 40% N reduction + biochar (N60+BC). Compared with N100, N reduction alone had no significant impact on the number of tillers and aboveground biomass of rice, exceptfor N60 which slightly reduced grain yield, while biochar incorporation tended to obtain higher tillers, aboveground biomass, and grain yield of rice compared with N reduction alone. The average contribution of biochar to grain yield on the basis of N80 and N60 were 5.8% and 7.7%, respectively. Notably, biochar incorporation further improved the agronomic N efficiency (54.5–309.4% over N100) and apparent N recovery (25.7–150.5% over N100) on the basis of N reduction. Furthermore, biochar application could not only maintain N nutrition level of rice, but also improve soil fertility mainly by increasing soil pH and organic matter. Therefore, integrated application of mineral N fertilizer and biochar is a feasible nutrient management measure to increase rice yield and soil fertility, and improve N use efficiency in paddy ecosystem. [ABSTRACT FROM AUTHOR]

Biochar is known to be a promising material for the treatment of contaminants in wastewater and soil. In this research, wastewater samples collected at the tertiary stage from a WWTP located in the North Bohemia region of Czechia and containing 20 pharmaceutical contaminants were treated with the same biochar (wood and maize cob feedstocks, pyrolysis temperature of 470 °C), but of different doses (0.1 g L−1, 0.25 g L−1, 0.5 g L−1). In this case study, we aimed to verify the impacts of biochar application and/or concentration on the sorption of pharmaceuticals in water. The treated water was later used for irrigating planted (ryegrass taken as the plant model) and unplanted agricultural soils in a pot experiment. Soils and ryegrass samples were examined again for potential pharmaceutical existence, and the soil microbial activities were determined through fluorescein diacetate hydrolytic activities (FDHA). Results showed that most pharmaceuticals concentrations were significantly, but not totally, reduced from the wastewater upon biochar addition. Contaminants such as 3-hydroxycarbamazepine and metoprolol were entirely removed from the wastewater after 0.25 g L−1, whilst bezafibrate did not decline even at 0.5 g L−1. Moreover, the concentrations of pharmaceuticals in ryegrass biomass and soils were dominantly below detection limits or at very low doses. Finally, there were no significant differences in the microbial activities of the soils. This implicates that biochar could be approached as a good substrate for eliminating pharmaceuticals from wastewaters used for agricultural irrigation; however, more similar studies need to be carried out. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is a common heavy metal contaminant which seriously affects plant growth and environmental safety. Biochar, as an organic soil amendment, has been shown to effectively mitigate Cd damage to plants. To study the effectiveness of biochar on mitigating Cd stress, Mentha piperita 'chocolate' and Mentha spicata were used in a pot experiment of Cd stress with a CdCl2 solution (10 mg Kg−1), while a biochar suspension (0, 40, 80, and 160 g Kg−1) was applied to the soil. The effects of Cd on the growth, physiological and biochemical properties, and Cd content in plant tissues of both mint species were found to be significant. The application of 40 g Kg−1, 80 g Kg−1, 160 g Kg−1 biochar significantly alleviated Cd damage to both mint species, increased plant height, leaf length, leaf width, biomass, photosynthetic rate, transpiration rate, stomatal conductance, and chlorophyll content, and decreased antioxidant enzyme activities (including superoxide dismutase, catalase, peroxidase, and polyphenol oxidase) and non-enzymatic antioxidant content (including flavonoids and total phenols). Biochar effectively reduced the Cd uptake by plants and decreased the migration and transformation capacity of Cd in the soil–plant system. In addition, the available nitrogen (available N), available phosphorus (available P), available potassium (available K), and pH in the soil increased after biochar application compared to non-biochar amended soil. The addition of 160 g Kg−1 biochar was shown to have the best performance of the application rates in this experiment and may be considered as an effective way to reduce the damage caused by Cd contamination to M. piperita 'chocolate' and M. spicata. [ABSTRACT FROM AUTHOR]

The agronomic benefits of biochar (BC) prepared by slow pyrolysis of vine pruning residues, which are produced in large quantities in Romania, were evaluated. Three soil types, i.e., slightly alkaline fluvisol (S1), slightly acidic chernozem (S2), and strongly acidic luvisol (S3), with mean values of pH of 7.99, 6.26, and 5.40, were amended with BC at a volumetric ratio between BC and soil of 20/80. A greenhouse experiment was performed for 109 days to assess the effects of BC amendment on bell pepper growth. The following treatments were applied: foliar fertilizer, BC, BC + foliar fertilizer (using two concentrations of foliar fertilizer solution), and a control. Strongly alkaline BC (pH of 9.89 ± 0.01) had a significant positive effect on the growth performance of bell pepper plants sown in the strongly acidic soil S3. The mean values of height, collar diameter, number of leaves, and root volume of plants grown in BC-amended soil S3 without foliar treatment were significantly higher (13–72% and 14–33%, respectively) than those of plants grown in non-amended soil S3 without and with foliar treatment. This beneficial effect of BC on bell pepper plant growth was due to the changes in the soil properties. BC significantly increased (up to eight times) electrical conductivity, pH, soluble phosphorus, potassium, and ammonium nitrogen concentrations of soil S3, and decreased its bulk density by 51%, resulting in improved water/nutrient uptake and plant growth performance. BC had no favourable effect on the growth parameters of bell pepper plants sown in slightly alkaline soil S1, and slightly acidic soil S2. [ABSTRACT FROM AUTHOR]

Modified biochars have attracted attention for reducing greenhouse gas emissions in paddy fields. However, material screening difficulties and lengthy effect validation periods have restricted their development. We proposed a theoretical calculation method to guide short-term field trials in this study. Utilizing first-principles calculations, we determined that sodium ferrate-modified biochar (Fe@C) would limit methane (CH4) and nitrous oxide (N2O) emissions. Field trials confirmed that Fe@C increased rice yields and active organic carbon content in soil and reduced methane emissions and the global warming potential. However, applying sodium ferrate alone significantly reduced N2O emissions. Correlation analysis showed that methane was significantly negatively correlated with yield and the soil carbon pool labile index. N2O was significantly negatively correlated with urease activity, and significantly positively correlated with the soil carbon pool management index. Therefore, Fe@C provides a high-yielding management measure that enhances soil labile organic carbon. Additionally, its effects were controlled by the proportion of sodium ferrate. Our work provides a new strategy to guide the design of paddy field experiments via theoretical calculations, greatly shortening research time and providing solutions for carbon sequestration and emissions reduction. [ABSTRACT FROM AUTHOR]

Doped compost consists of compost inoculated with Bacillus siamensis SCFB3-1 that is formulated in biochar and then mixed with the compost. The study objective was to analyze, at field scale, the effect of doped compost on the melon and pepper yield and on the soil microbiome, hypothesizing that the synergy between the components of doped compost confers additional benefits to the crop. Two doses of compost (2 and 5 t/ha) and two doses of the inoculant (biochar+SCFB3-1) with respect to the compost (3% and 6% w:w) were tested. The highest yield was observed for a reduced dose of mineral fertilization (NPK -20%) with a compost dose of 2 t/ha with 6% of the inoculant. Specifically, the yield increase compared with the control, which only received NPK, was a 47% increase in melon and 28% in pepper. The microbiome of the bulk soil was not modified by the doped compost, but the composition of the rhizosphere microbiome changed, increasing in the abundance of Bacillus (the inoculated strain), but also changing the relative abundance of other genera in the bacterial community. Future works will be focused on unravelling the possible effects of phytohormones on the observed results. [ABSTRACT FROM AUTHOR]

A two-year experiment was carried out at Shenyang Agricultural University's research field area in China to evaluate the impact of the combined application of straw mulch (0 and 8 t ha−1) and biochar (0, 4, 12, and 36 t ha−1) on the morphological traits and grain development of rainfed maize during 2018 and 2019. The results showed that straw mulch and different biochar application rates significantly impacted the maize growth index. Compared to non-biochar-treated soils, the introduction of straw mulch improved plant height, stem diameter, leaf area index (LAI), leaves, stem, root, and crop growth rate (CGR), and dry weight of rainfed maize crop. The highest plant height, stem diameter, LAI, leaves, stem, root growth rate, CGR, and dry weight of rainfed maize crop were reported when soil was treated with a higher rate of biochar (36 t ha−1). Biochar increased grain filling rate while decreasing grain filling duration in rainfed maize crops. Our results indicate that straw mulch and biochar-based soil management strategies can improve the rainfed maize growth with the environmental benefits of global warming mitigation. However, due to the wide range of biochar properties, the interactions between straw mulch and biochar should be given special consideration in the maize cropping system. [ABSTRACT FROM AUTHOR]

The use of organic amendments to enhance plant growth is increasing due to horticulture activities and vegetable cultivation in urban areas. Consequently, as organic amendments impact heavy metal solubility and plant uptake of unknown contaminants, the risk of human exposure to potentially toxic elements from contaminated soils and compost is increasing. Biochar co-application with compost may reduce the risk-related increased metal uptake by edible plants. To verify this thesis, a greenhouse experiment was established to examine the effects of rabbit-manure-derived biochar (RBC) on Cu, Cr, Cd and Pb uptake by five green leafy vegetables (lettuce—Lactuca sativa L., spinach—Spinacia oleracea L., corn salad—Valerianella locusta L., kale—Brassica oleracea L., mustard greens—Brassica juncea L.) cultivated in compost substrate and soil amended with a 30% (v/w) mix of compost and biochar. The results indicated that the addition of biochar decreased Cu, Cr, Cd and Pb availability in the tested substrates, reducing the uptake of Cd in spinach by 61% and Pb in mustard greens by 73%. The application of RBC also had some adverse effects, such as enhanced accumulation of Cr by kale, lettuce and mustard greens cultivated in compost. Compost co-application with biochar to soil decreased the availability of metals, reducing the content of Pb and Cd in tissues of the tested vegetables, while uptake of Cu and Cr was enhanced in spinach and lettuce by 20%. In conclusion, the application of compost and biochar can be beneficial in improving the quality of urban soil used for horticulture purposes. However, more attention by gardeners should be paid to soil and compost testing in terms of heavy metal contamination and possible adverse effects of organic amendments application for green leafy vegetable cultivation. [ABSTRACT FROM AUTHOR]

Livestock farmers are seeking ways to lower their environmental footprints by reducing inputs, lowering greenhouse gas emissions, and enhancing carbon sequestration. To meet these objectives, farmers are investigating the value of diverse multispecies grazing swards and various organic by-products as alternative fertilizers and soil amendments. This study investigated the effects of HexaFrass™ [HexaFly, Meath, Ireland], an insect frass based organic fertilizer, and biochar, a form of charcoal, on the shoot dry matter accumulation of two forage plants, chicory and ribwort plantain. Under glasshouse conditions, HexaFrass™ generally increased the shoot growth of both chicory and plantain, although these positive effects were lost if an excessive amount of HexaFrass™ was applied, or the growing medium was already nutrient-rich. Importantly, it was found that HexaFrass™ also increased the re-growth of shoots after cutting, which is vital for plants that are destined to be successfully used in grazing or silage swards. Biochar had a less obvious effect on the shoot dry matter accumulation, although there was some evidence of a synergy between biochar and HexaFrass™, which caused an additional increase in the shoot growth. The results indicate that frass-based fertilizers could play a role in low-input mixed swards, whereas the potential of biochar as a soil amendment in these grazing systems requires further research. [ABSTRACT FROM AUTHOR]

The conversion of bio-wastes to useful products such as biochar provide a suitable option not only to minimize the mass of wastes, but also to use the biochar as soil amendment. In the present study, food waste biochar (FWB) and agricultural waste derived biochar (AB), either alone or in combination (FWB + AB), were tested for their effects on soil microbiological characteristics (soil enzymes, soil basal as well as substrate-induced respiration), plant growth and photosynthetic parameters. Four treatments were tested: control, FWB, AB and FWB + AB. The results indicated that the application of AB significantly enhanced the plant above ground and below ground fresh and dry biomass as compared to other amendments and control (+41 to +205% compared to control). The application of FWB enhanced the quantum yield of photosystem II (QY-max, +4% compared to control) and normalized difference vegetation index (NDVI, +13% compared to control). Moreover, the FWB application improved the soil dehydrogenase (DHA) activity (+24% compared to control). Furthermore, the soil basal respiration was found to be increased under AB application (+46% compared to control) and the substrate-induced respirations were relatively decreased, depicting negative effects of applied biochars on substrate-induced respirations. Thus, we concluded that the differential responses of observed crop and soil attributes might be related to the biochar specific effects on soil properties. [ABSTRACT FROM AUTHOR]

Water scarcity is one of the most limiting environmental factors for crop productivity globally, where biochar application can play a role. To test this, a glasshouse experiment was conducted with aged biochar application with water regimes on arbuscular mycorrhizal fungi colonisation, plant growth, phosphorus nutrition and leaf gas exchange in wheat and subterranean clover. Six treatment combinations (two biochar levels of 0 and 6 t ha−1; and three water regimes of well-watered, water-stressed and watering intermittently) were arranged in factorial completely randomized block design with three replications. The wheat and subterranean clover were grown and harvested 14, 24, 34 and 44 days after sowing. In this study, aged biochar had no significant effect on plant growth for both wheat and clover, regardless of water regimes. Shoot and root dry weights increased in well-watered conditions compared to water-stressed conditions. Root length and colonised root length increased with biochar addition for wheat, mostly in well-watered treatment. Phosphorus uptake increased in biochar treatment, and the effect was higher in well-watered conditions. Leaf photosynthetic rate (PN), stomatal conductance (gs), intercellular CO2 concentration (Ci) and transpiration rate (E) increased with biochar addition. For clover, the effect was higher in water-stressed than well-watered conditions. These results suggest that biochar may enhance water availability to clover plants in water-stressed conditions. However, the positive effect of biochar on plant growth under water-stressed conditions, varied with plant species, needs to be explored further in a range of crop species and biochar sources in addition to the material used in the current investigation. [ABSTRACT FROM AUTHOR]

To solve the problem of nitrogen loss and harmful gas emissions in the co-composting of cyanobacteria with other wastes and agricultural non-point source pollution in the Chaohu Lake Basin (CHLB), this study selected cyanobacteria as the main material, spent mushroom and rice hulls as excipients, and biochar (B) and Mg2+/PO43− salt as an additive. The nitrogen fixation rate, maturity, toxicity, and fertilizer efficiency indexes were analyzed to explore the best rate of biochar application. Additionally, three different fertilization treatments (C0: No fertilization, CF: Chemical fertilizer, OF: Organic fertilizer) were applied to agricultural field experiments in the CHLB. The results showed that the cyanobacteria composting experiment with 10% B as additives had the lowest cumulative NH3 emission (603.00 g) and the highest nitrogen fixation rate (61.54%). We used this compost product for maize cultivation in field experiments. The results show that OF treatment can reduce field nutrient loss, and the increase in the rate of soil TN fixation was as follows: OF (18.62%) > CF (10.34%) > C0 (−9.66%). Moreover, the TN and TK losses in runoff were 33.33% and 22.74% lower than CF in farmland runoff. The OF treatment increased the content of crude fat, crude protein, and crude starch by 4.40%, 8.34%, and 2.66% compared with the CF treatment, respectively. Overall, the N, P, and K source agronomic coefficients of cyanobacteria organic fertilizer were 1.424, 1.001, and 1.16, respectively. These results indicated that cyanobacterial organic fertilizer could replace chemical fertilizer to reduce agricultural non-point source pollution and improve maize quality. Meanwhile, the amendment of B and Mg/P salt additives could reduce air pollution and improve the quality of compost products. This study provides a theoretical basis and reference for nitrogen fixation and extension of multiple wastes co-composting field experiments. [ABSTRACT FROM AUTHOR]

The recovery of phosphorus (P) from milk processing flotation sludges (MFS) using pyrolysis can contribute to a sustainable reuse of P by converting waste to fertiliser. The objectives of this study were to quantify the recovery and transformation of P following MFS pyrolysis and compare the efficacy of raw and pyrolysed MFS as organic P fertilisers. Phosphorus retention in biochars was high (98 ± 0.73% yield), leading to the enrichment of P relative to the raw MFS by a factor of 4.3–4.5. Pyrolysis of the MFS at 450 °C led to a 3-fold increase in the proportion of P in the HCl-extractable fraction (65 ± 0.32%), a 2-fold reduction in NaOH-P (30 ± 2.1%), and negligible amounts of P in the H2O-P and NaHCO3-P fractions. The bioavailability of P in raw MFS and 450 °C biochar was compared to a soluble P fertiliser in P-limiting plant bioassays. In the short-term (70 day) trial where ryegrass was grown on three soil types (Arenosol, Vertisol or Ferralsol), biochar MFS showed higher efficacy as a P fertiliser than raw MFS in the acidic Ferralsol, whereas the opposite response was observed in the near-neutral Arenosol. In the Vertisol, neither the raw MFS nor biochar produced more cumulative biomass or P uptake than any of the nil P controls. Over a longer 200-day period, raw MFS and biochar applied to the Arenosol were about 20% as efficient at providing P to ryegrass plants as the water-soluble K2PO4, suggesting that higher application rates of MFS or biochar would be required to match synthetic fertilisers in the short term. [ABSTRACT FROM AUTHOR]

The effects of olive waste biochar and green compost as soil amendments on soil physical properties, as well as on physiological parameters and yield of a super-intensive olive crop cultivated under deficit irrigation conditions, were investigated in south-west Spain during the 2021 growing season. Thus, soils were amended with 40 t ha−1 of olive pomace waste biochar, green-compost, or a biochar-compost mixture (50% w/w), and no amended plots were used as control. On a bi-monthly basis, soil pH, water holding capacity, humidity, and resistance to penetrability were determined. In addition, various indicators of the physiological status and water stress of the plant were also monitored. Finally, the olive yield per tree was measured. Results showed that biochar application was the most effective amendment for increasing soil moisture and reducing soil compaction. The latter was evidenced by the significant reduction of the resistance to the penetrability of the amended soils. Plants of the amended plots showed better leaf water potential. In addition, values of the net photosynthesis rate, the average intrinsic water-use efficiency, and the maximum rate of electron transport in the time before the harvest improved significantly in the trees from the biochar-amended plots, for which olive fruit yields increased by about 15% in comparison with the other treatments. Nevertheless, the estimated net oil yield per tree was similar because the olives from the biochar-amended trees contained more moisture. This field trial shows for the first time that by providing the soil with biochar from olive crop waste as an organic amendment, having high water retention capacity, porosity, and stability, it would be possible to reduce the irrigation water needed and maintain plant yields. [ABSTRACT FROM AUTHOR]

Continuous use of chemical fertilizers has deteriorated soil health and crop productivity. Replenishing soil nutrients and microbial activity with eco-friendly soil amendments such as biochar and manure is therefore necessary to sustain soil health for crop production. However, studies are limited regarding the evaluation of biochar and poultry manure effects on soil health, attributed mainly to microbial extracellular enzymes and respiration. Therefore, the present study was designed to investigate the effects of poultry manure and biochar on soil physico-chemical and microbiological properties and lettuce biomass accumulation in a pot experiment. The pots were amended with poultry manure either alone and or in combination with low (10%) and high (20%) rates of biochar. The treatments included were; (i) control, (ii) manure alone (M), (iii) manure plus 10% biochar (M + B10, and (iv) manure plus 20% biochar (M + B20). Results revealed that soil extracellular enzymes related to C, N, and P mineralization, soil basal (BR), and substrate induced respirations (SIR) were significantly affected by applied manure and manure–biochar. However, there were large differences observed for applied amendments regarding various soil and crop parameters. Specifically, the manure combined with a high rate of biochar (M + B20) enhanced total carbon (TC) content, dehydrogenase activity (DHA), BR, and all SIRs except Arginine-IR. On the other hand, manure combined with a low rate of biochar (M + B10) resulted in enhanced lettuce aboveground dry biomass (AGB-dry). The manure treatment alone (M), however, proved to be the most influential treatment in improving soil enzymes (β-glucosidase, N-acetyl-β-d-glucosaminidase and phosphatase) involved in C, N, and P mineralization compared to the other treatments and control. Thus, it was concluded that the sole application of M and M + B20 improved both fertility and soil health, which therefore could be a promising direction for the future to enhance soil quality and crop productivity. [ABSTRACT FROM AUTHOR]

The investigation of the mechanisms organic matter transformation in compost organic fertilizers is an urgent task of modern soil ecology and soil chemistry. The main components of such fertilizers are newly formed, weakly humified labile humic acids (HAs). The objective of the study is to determine the mechanism of converting the newly formed HAs into the forms with increased resistance to microbiological and biochemical influences. Obtained during the plant residues decomposition, HAs were studied in the incubation experiment (0, 30, 90 days). Calcium carbonate and biochar produced by rapid pyrolysis from birch and aspen wood, at 550 °C, were used as the composting mixture compounds. Decomposed plant residues—fresh aboveground mass of clover (Trifolium pratense L.), rye (Secale cereale L.), as well as dry oat straw (Avena sativa L.) were the material used for humification. To obtain Has, 0.1 M NaOH and 0.1 M Na4P2O7 were used. Then, HAs were separated from fulvic acids (FAs) using a 0.5 M H2SO4. The amount of labile HAs (HAs1) was estimated by their content in 0.1 M NaOH. The amount of stabilized HAs (HAs2) was calculated by the difference between the HAs content in 0.1 M Na4P2O7 and 0.1 M NaOH. Preparation of HAs for elemental composition and NMR analysis was performed according to the International Humic Substances Society's recommendations. The possibility of converting newly formed HAs into stable forms (calcium humates), whose share in the HAs composition reaches 40–50%, has been shown. However, the mechanism of HAs transformation under the studied reagent's influence was different. In the presence of calcium carbonate, it is caused by the physicochemical processes of newly formed HAs rearrangement. However, in the presence of biochar, this is due to the humification processes' intensification and to the increase in the aromatization degree confirmed by the increase in the optical density, as well as by the increase in carbon and oxygen proportion, and by the decrease in hydrogen proportion in HAs molecules. The understanding of HAs formation and transformation mechanisms at the early humification stages can help to optimize the methods of obtaining organic fertilizers. [ABSTRACT FROM AUTHOR]

Chemical nitrogen (N) fertilizers are regarded as one of the environmental contaminants in addition to the necessity for fossil sources for their production. Conversely, it is impossible to neglect the supply of nitrogen needed as one of the essential ingredients for plant function. For organic agriculture, it is crucial to use alternative fertilizer management to reduce the harmful impacts and production costs of chemical fertilizers. In a one-year pot experiment, nitrate (NO−3) leaching and nitrogen efficiency of wheat were examined in relation to biochar (B) mixed with urea (U), legume residues (L), and azocompost (A), which represent chemical, green, and biological sources of N-fertilizers, respectively. Control (no biochar, no fertilizer), U (46 kg ha−1), A (5 t ha−1), L (5 t ha−1), B (10 t ha−1), UB, AB, and LB were the experimental treatments. Grain yield of wheat was enhanced by 337% and 312% with UB and UL, respectively. The LB produced the highest grain N yield, with a rise of 8.8 times over the control. L had the highest N-use efficiency, with an increase of 149% over the control. The highest N-harvest index and N-recovery efficiency were obtained by using LB, with values of 91 and 70 %, respectively. Nitrate leaching occurred in the following order: U > Control ≥ A ≥ L > UB > AB ≥ LB > B. Nitrogen is retained for the plant in the extensive specific surface of biochar when N-fertilizers are used in conjunction with them. This not only improves N-efficiency but also minimizes nitrogen loss through leaching. Additionally, the soil can benefit from the addition of leguminous organic fertilizer in a similar way as to urea fertilizer in terms of increasing wheat grain yield, particularly when combined with biochar. [ABSTRACT FROM AUTHOR]

From the perspective of sustainable agri-food production, farmers need to make the best use of natural resources. Biochar can be a solution to adopt a more sustainable way of farming. Despite its environmental and agronomic advantages, biochar has a low plant nutrient value. This study evaluated the effect of biochar and the co-application of an inorganic or organic fertilizer on the soil properties, growth and nutrient content of Swiss chard (Beta vulgaris L. var. cycla, Caryophyllales order, Chenopodiaceae family). The experiment consisted of two factors: biochar type (from vineyard prunings and wood chips) and fertilizing source (ammonium nitrate and vermicompost). Biochars were applied at a 2% rate (w/w) and fertilizers at a dose providing 280 kg N ha−1. The soil properties (pH, EC, extractable anions, cations, total N, Corg and C/N ratio) were measured before the plants were transplanted and at the end of the growing cycle, along with the growth parameters (leaf number, length and fresh weight) of each leaf cut, the productive parameters (total number of leaves and yield per plant) at the end of the growing cycle and the leaf content of anions (NO3−, P2O43−, SO42−), cations (NH4+, Na+, K+, Ca2+, Mg2+) and total N. The co-application of biochar and a fertilizing source had a positive effect on soil properties and leaf nutrient content. Vermicompost increased plant growth by 22% and plant yield by 116%, in contrast to biochar, and increased limited leaf NO3− accumulation by about 81% in comparison to ammonium nitrate. The co-application of biochar and vermicompost is the better option to increase Swiss chard yield while preserving the nutritional and health qualities of the product. [ABSTRACT FROM AUTHOR]

Abiotic stresses are the most significant factors reducing agricultural productivity. Plants face extreme environmental conditions that may affect their biological mechanisms, thereby influencing their growth and development. Microorganisms possess substantial metabolites that aid in helping plants mitigate abiotic stresses. Plants' interaction with microbes constitutes a diversified ecosystem, as sometimes both the partners share a mutualistic relationship. Endophytes, plant-growth-promoting rhizobacteria (PGPRs), and arbuscular mycorrhizal fungi (AMFs) are examples of microorganisms that play an essential role in alleviating abiotic stresses and, hence, improving plant growth. The plant–microbe interaction leads to the modulation of complex mechanisms in the plant cellular system. Moreover, the residing microbial flora also inhibits the phytopathogens, therefore, it becomes part of plants' innate defense system. Keeping in view the growing environmental concerns, it is important to identify the role of the plant microbiome in the transportation of nutrients to maintain sustainable production. Furthermore, it is important to identify the factors enabling plants to recruit beneficial microbial species and how to deal with the potential pathogens. Therefore, this review aims to summarize the impacts of various abiotic stressors on agricultural productivity and the role of beneficial microorganisms in mitigating the negative effects of abiotic stresses. The literature review also shows that the beneficial microbes, including PGPRs, AMFs, and endophytes, adopt various mechanisms for ameliorating the negative effects of various stresses. It has been observed that biochar and microbes, either individually or in combination, can play a significant role in maintaining plant growth under stress conditions. Although conventional inoculation of beneficial microbes mitigates abiotic stresses and enhances productivity, the advancement in genetic engineering would help transfer specific genes from the microbes to plants to aid in abiotic stress mitigation. [ABSTRACT FROM AUTHOR]

Biochar fertilization improves soil fertility and carbon sequestration, implying agricultural and environmental advantages. The effect of different sized previously applied biochar and biofertilizer agents on succeeding crops remains poorly known for legume–cereal cropping cycles. This study compared different particle-sized biochar and biofertilizer strains applied to lentils for their residual impact on subsequent maize growth, nutrition, and soil fertility without further polluting the environment. Three particle sizes (<2, 2–5, 5–10 mm) of Babul tree (Acacia arabica) wood biochar was obtained through grinding and sieving and applied prior to the lentil (first) crop at a rate of 500 g m−2. The commercial Rhizobium leguminosarum products Biozote-N and Rhizogold were inoculated to lentil seeds before sowing. The effect of biochar and biofertilizer agents on the succeeding maize (second) crops was evaluated for soil and crop performance. Findings revealed that particle sizes of <2 mm biochar and Biozote-N inoculation enhanced plant height, leaf area and leaf area index, biological yield, and thousand grain weight of the subsequent maize crop. Maize grain yield was enhanced by 2.5%, tissue N uptake by 15%, nitrogen uptake efficiency by 17%, grain protein content by 15%, extractable P by 17%, and soil bulk density by 3% with a residual biochar particle size of <2 mm and Biozote-N inoculation. It was concluded that the finely grounded (<2 mm) biochar particle combined with inoculation of Biozote-N was superior to larger particle sizes for enhancing crop growth and improving soil fertility status at the residual level, benefiting the subsequent crop in a legume–cereal rotation system. [ABSTRACT FROM AUTHOR]

The aim of this work was to compare the application of biochar, compost, and their mixtures on soil fertility and crop yields using a volcanic Mediterranean soil. For this reason, three types of organic amendments (OAs) were selected: compost1, made from olive mill waste and orchard pruning residues; compost2, made from olive mill waste, animal manure and wool residues; and biochar made from beech wood pyrolyzed at 550 °C. When selected, the OAs were characterized chemically for organic carbon (OC), total N, pH, electric conductivity (EC) and the bulk fraction of organic matter using 13C CPMAS NMR spectroscopy. In addition, soil chemistry was analysed at the end of each year for the following parameters: pH, OC, total N, CaCO3, P2O5, NH4, FDA and EC. Results showed that biochar had the highest OC and the lowest N and EC compared to both composts. Moreover, 13C CPMAS NMR showed that biochar had the lowest content of O-alkyl, methoxyl- and alkyl-C and the highest content of aromatic-C. On the other hand, compost2 and compost2+biochar mixture reduced Aubergine yield by −60% and −40%, respectively, and tomato yield by −50% and −100%, respectively. Nevertheless, a significant increase in onion and rape yields were observed when compost1, compost1+biochar and compost2 were applied, while biochar and compost2+biochar significantly decreased the yield of these crops. Overall, our results highlight that the effect of OAs on crops yield is largely variable and influenced by the interaction with soil chemistry. [ABSTRACT FROM AUTHOR]

Research is still under-represented for the long-term impacts of field biochar application on soil fertility, rice production and mineral nutrition and soil C sequestration. To investigate these effects, a field trial was established in the fall of 2010 with low (2.4 t ha−1), intermediate (6 t ha−1) and high (12 t ha−1) biochar doses. The biochar effect on soil nutrients is more pronounced in the surface soil and is dose dependent. In the surface soil, biochar application increased the availability of soil N, P and K. High dose decreased soil total Fe by 11.6% and Mn by 20.7%, leading to a slight but insignificant decrease in grain Fe and Mn concentration. The intermediate and high doses significantly increased the soil available Zn by 96.2% and 227.9% but did not affect the grain Zn concentration. Grain Cu concentration was significantly decreased by the intermediate (−19.6%) and high (−14.3%) dose of biochar. Biochar had a slight but insignificant boost on rice yield. Soil total C and N increased linearly with biochar application for the surface soil only where biochar was applied. In conclusion, with great soil C sequestration capacity, the long-term field return of biochar is beneficial for improving the soil macronutrient and Zn fertility, but caution is needed, as higher doses of biochar could potentially lead to a decrease in soil Fe and Mn and a reduction in grain Cu concentration. [ABSTRACT FROM AUTHOR]

Alkali-enhanced biochars, as an environment-friendly material, combine the advantages of biomass nutrients and carbon fixation. In this study, rice-residue-derived biochars were evaluated for P and C solubility and their amendment upon plant P uptake. Biochars from rice straw (RS) and husk (RH), including raw biochar without alkaline pretreatment (0B), alkali-enhanced biochars with KOH (5KB, 5 g KOH per 100 g feedstock;10KB, 10 g KOH per 100 g feedstock), K2CO3 (5K2B, 5 g K2CO3 per 100 g feedstock; 10K2B, 10 g K2CO3 per 100 g feedstock), and CaO (5CB, 5 g CaO per 100 g feedstock; 10CB,10 g CaO per 100 g feedstock) were prepared at 350 °C~550 °C pyrolysis conditions. Alkali-enhanced biochars on soil water soluble P(WSP) and C(WSC) levels were assessed through a soil-biochar incubation experiment. The effect of alkali-enhanced biochar on rice P uptake was evaluated in a greenhouse pot study. The WSP content in KOH- and K2CO3-enhanced biochars produced at 550 °C was significantly increased by up to 144% compared with that produced by the corresponding biochars at 350 °C, while the WSC content in all alkali-enhanced biochars (except for RS-5CB) prepared at 550 °C significantly decreased by up to 6426% compared with that produced by the corresponding biochars at 350 °C. The application of 3% 10KB and 10K2B rice straw biochars (produced at 550 °C) significantly elevated the WSP content in soils. Rice grown in the RH-10K2B-550 treated soil significantly increased the grain P uptake by 15% and 8% compared with RH-0B-350 and RH-10K2B-350, respectively. The water soluble P of the KOH- and K2CO3-enhanced biochars increased with increasing the pyrolysis temperature. RS-10KB and RS-10K2B increased the soil WSP and WSC content compared with the unenhanced biochar (RS-0B), and showed a clear positive effect on increasing the rice P uptake. Overall, KOH- and K2CO3-enhanced biochars pyrolyzed at 550 °C as Si sources could also serve as a potential P pool with multi-functions in C sequestration and K nutrition. [ABSTRACT FROM AUTHOR]

Biochar application has been considered as a promising solution to address the effects of modern agriculture on climate change. However, there is a lack of research on the biochar application of greenhouse gas emissions based on poor soils in Korean agricultural land. Therefore, this study aimed to evaluate the effects of biochar application according to different soil characteristics on soil organic carbon (SOC) improvement and greenhouse gas reduction. The incubation experiments were conducted for 49 days and used different feedstock (barley straw and poultry manure) and biochar application rates (0, 5, 10, and 20-ton ha−1) in four soil characteristics (upland, U; greenhouse, G; converted land, C; reclaimed land, R). The results of this study showed that the SOC increased significantly in all soils after biochar application. The increasing SOC rate was the highest in poor soil. Biochar 20-ton ha−1 treatment significantly reduced N2O emissions by 33.2% compared with the control. Barley straw biochar significantly reduced N2O emissions from all soils. Barley straw biochar decreased approximately 74.5% of N2O emissions compared with poultry manure biochar. Poultry manure biochar improved SOC and reduced N2O emissions in poor soil. However, in poultry manure biochar treatment in U and G soil, N2O emissions increased. In conclusion, barley straw biochar application was found to suppress N2O emissions and improve the SOC in all soil characteristics of agricultural land. In addition, the soil carbon storage effect and N2O reduction effect of biochar were the highest in poor soil. Thus, the biochar application can be a potential agricultural practice for improving soil quality and decreasing N2O emissions in domestic agricultural soil. [ABSTRACT FROM AUTHOR]

Biochar addition has been proposed to influence soil nitrogen (N) cycle and improve crop productivity. However, a comprehensive understanding of the impact of soil N cycle on the productivity of different crops under biochar addition remains elusive. Thus, a meta-analysis of 93 peer-reviewed field experiments was undertaken to investigate these outcomes of biochar addition. Results show that biochar addition significantly enhances crop productivity by 13.0%. The productivities of legumes, maize, and wheat were significantly increased by 21.2%, 14.3%, and 8.00% following biochar addition in the fields, respectively. However, the improvement in rice productivity is the lowest (3.36%), insignificant following biochar addition. The aggregated boosted tree, and partial least squares path analyses, indicated that the changes in the soil N pool (i.e., TN, NO3−-N, and NH4+-N) and plant N uptake were the most critical factors in increasing crop productivity under biochar addition. Although biochar addition had no significant enhancement on rice productivity, enhancing field rice nitrogen uptake and modest application of nitrogen fertilizers greatly improved rice productivity. The amount of soil NH4+-N was vital to improving legume productivity rather than biological N2 fixation when biochar was applied. Increases in NH4+-N content and decreasing NO3−-N content were favorable to improving maize productivity under biochar addition. In contrast, biochar additions did not significantly regulate the parameters and processes of soil N cycle to enhance wheat productivity. Overall, the productivity of different types of crops is greatly influenced by soil N cycle under biochar addition. [ABSTRACT FROM AUTHOR]

The paper aimed at evaluating the effects of biochar (BC) produced by slow pyrolysis of vine pruning residue on soil physicochemical properties and tomato plant growth. A greenhouse experiment was conducted for 66 days, applying different treatments for 3 soil types, i.e., foliar fertilizer, BC (at a volumetric ratio between BC and soil of 20/80), BC + foliar fertilizer, and no treatments. Strongly alkaline BC (pH = 9.89 ± 0.01) had a significant beneficial effect on the growth performance of tomato plants sown in a strongly acidic soil (pH = 5.40 ± 0.02). The mean values of height, number of leaves, and collar diameter of plants grown in BC-amended soil without foliar treatment were up to 50% higher than those of plants grown in soil with the other treatments. This positive effect of BC on plant growth is due to the changes in the soil properties. The addition of BC led to increased values of electrical conductivity, pH, soluble and available nutrient concentration. Moreover, BC reduced soil bulk density by about 50%, resulting in improved plant root development and thus enhanced water and nutrient uptake. Accordingly, BC derived from vine pruning residues can improve soil quality and tomato plant growth, as well as reduce biomass residues. [ABSTRACT FROM AUTHOR]

The tea root system plays a key role in the uptake of nutrients and water from the soil. The effect of integrated fertilizers (Control (CK) (no fertilizers), 100% NPK, 100% NPK withbiochar (NPK + B), 50% NPK with 50% rapeseed cake (NPK + RC), and 100% rapeseed cake (RC))on alterations in root growth characteristics and soil physical properties, nutrient uptake, NUE, and biomass production of tea (Longjing 43) was studied in an Alfisol at the greenhouse of the China Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou, during 2020–2021. The results showed that the conjunctive application of mineral fertilizers with rapeseed cake (NPK + RC) resulted in significant (p < 0.05) reductions in soil penetration resistance (14.8%) and bulk density (8.7%) and improvement in porosity (9.9%) compared to the control. NPK + RC recorded significantly higher (p < 0.05) root surface area, root volume, root tips, root length, and root CEC of tea than NPK (15%, 20%, 27%, 6%, and 11%) and control (40%, 165%, 49%, 68%, and 12%). The combinedapplication of RC and NPK fertilizer significantly decreased the specific root surface area (137%) and specific root length (66.8%) compared to the control. Root, stem, leaves, and total biomass were improved by integrated fertilization compared to the control and mineral fertilization. The nutrient content (N,P,K), nutrient uptake, NUE, nutrient uptake per root length, volume, and surface area of tea plants under NPK + RC and NPK + B were significantly (p < 0.05) higher than RC and CK. Therefore, the integrated use of rapeseed cake with mineral fertilization in Alfisol should be practiced in tea plantations to improve soil physical environment, root proliferation and root CEC, nutrient uptake, and NUE and achieve higher tea biomass production through the efficient exploitation of nutrients. [ABSTRACT FROM AUTHOR]

Background: Knowledge of the responses of soil aggregates to various fertilization practices can contribute to sustainable soil management in urban vegetable agriculture. Aims: The study assessed the soil fertility, dry aggregate stability, and aggregate total carbon (TC) and nitrogen (TN) retention after the reapplication of biochar, and organic/inorganic fertilizers. Methods: Four replicates of ecological sanitation (ECOSAN) manure, NPK fertilizer, corncob biochar (CCB), and CCB, combined with urea and cattle manure (UCF), were established in a randomized complete block design. Results: The application of ECOSAN increased the soil pH and also resulted in significant accumulation of available phosphorus (P), calcium (Ca), and magnesium (Mg). Compared to CCB treatment, UCF + CCB produced significant increases in the TC, TN, P, Ca, and Mg concentrations by 53, 140, 227, 27, and 78%, respectively, and additionally increased the 4.75–2.00 mm large macroaggregates and mean weight diameter. The total carbon increased significantly in microaggregates (>0.25 mm); macroaggregates (4.75–0.25 mm); and in the micro- and macroaggregate fractions of the ECOSAN, CCB, and UCF + CCB treatments, respectively. More so, the TN in micro- and macroaggregates was increased maximally by UCF + CCB and minimally by the CCB treatment. Conclusions: The reapplication of CCB had limited potential for carbon sequestration in soil aggregates, but its combination with UCF better reflects carbon and nitrogen stabilization in micro- and macro- aggregates, with greater potential in large macroaggregates. [ABSTRACT FROM AUTHOR]

Biochar represents a stable form of carbon-rich organic material produced by the pyrolysis of various biomass residues. It has the potential to stabilize organic carbon in the soil and improve soil fertility, water retention, and enhance plant growth. Despite its potential, there is limited information on the mutual relation of biochar texture with its physicochemical characteristics, morphology, and the content of organic matter. For these reasons, we studied three biochar samples with potential use in agriculture as soil supplements (NovoCarbo, Sonnenerde, Biouhel.cz). Our experimental approach performed on the individual sieved fraction of studied biochars (<0.5; 0.5–2.0; 2.0–4.0 and >4.0 mm) confirmed the importance of a selection of optimal source biomass material as the content of lignin, cellulose, and hemicellulose, together with the conditions of pyrolysis (temperature of pyrolysis), play a crucial role in the managing of the properties of produced biochar. Agronomically more stable biochars containing a higher content of organic matter and organic carbon, with alkaline pH response and well-developed aromatic porous structure, could be produced from lignin-based biomass residues at higher pyrolysis temperatures, which is an important finding taking into account the possible utilization of biochar in soils as a soil conditioner. [ABSTRACT FROM AUTHOR]

The performance of biochar application in water conservation, salt distribution, water infiltration, and tomato growth was evaluated under regulated deficit irrigation (RDI) (40%, 60% and 80% of ETc) and partial root drying (PRD) systems by using different quality irrigation water. Date palm derived biochar was applied to sandy soil at 4% (w/w) in pots, and tomato was grown as the test crop under greenhouse conditions. The results indicated that soil moisture was decreased by 27.38% to 24.95% without biochar application at different levels of irrigation, whereas it increased by 8.11% and 5.48% with biochar application, compared with control treatment of 100% of ETc. Soil moisture was decreased by 12.78%, 15.82% and 12.78% for the 1st stage, 2nd stage and 3rd growth stage, respectively, while it increased by 37.93% at the 4th growth stage compared with full irrigation. Soil salinity ranged between 0.5 and 1.4 dS·m−1 with biochar application, while 0.7–2.1 dS·m−1. Cumulative infiltration at one minute varied between 1.89 and 2.79 cm and 1.74 and 2.79 cm for biochar and non-biochar treatments, respectively. Infiltration rate varied from 0.98 to 2.63 cm min−1 and 1.48 to 1.68 cm·min−1 for fresh and saline water, respectively. Overall, the results revealed that biochar application substantially improved the characteristics of sandy soil, subsequently resulting in water conservation. [ABSTRACT FROM AUTHOR]

Drip fertigation with reduced fertilizer and water inputs has been widely used in greenhouse vegetable production in China. However, farmers usually do not apply additional organic material with a high carbon content, although soil organic carbon (SOC) concentrations are mostly below the optimum level for vegetable production. Returning straw or biochar to fields is an effective strategy for sustainability and environmental friendliness. We tested whether drip fertigation, (DIF) combined with maize straw (DIF+S) or biochar (DIF+BC), is a suitable option to improve SOC sequestration over eight growing seasons, and how these options affect soil N2O emissions and yields or partial factor productivity of applied N (PFPN) of crops over three growing seasons. During the winter–spring growing season, DIF+BC significantly reduced soil N2O emission by 61.2% and yield-scaled N2O emission by 62.4%, while increasing the tomato yield and PFPN compared with DIF. Straw incorporation had similar trends but without significant effects. Conversely, straw and biochar incorporation increased N2O emission during the autumn–winter season. The structural equation model indicated N2O emission was dominantly driven by soil NH4+-N concentration, temperature and moisture. The N2O emission factor decreased significantly with increased PFPN. Moreover, the contribution of biochar to the increased SOC was approximately 78%, which was four times higher than that of straw incorporation. Overall, the results highlighted the potential of drip fertigation with biochar incorporation to mitigate N2O emissions, improve PFPN and significantly increase SOC storage, which could all contribute to maintaining environmental sustainability and soil quality of greenhouse vegetable production. [ABSTRACT FROM AUTHOR]

Biochar application is a promising sustainable strategy for enhancing soil properties thus crop production. However, biochar application to soil certainly alters its biological and physical properties, and could require extra costs. Therefore, biochar suitability to agroecosystems must be proactively estimated. The advantage of biochar addition to poor fertile or weathered soils has been well studies, however, its feasibility to fertile soil under low quality (saline) irrigation water was not frequently studied. Consequently, this work investigates the hypothesis of whether the application of biochar at a rate of 4.8 tons/ha to fertile soil (Nile Valley, Giza, Egypt) would ameliorate the negative effects of saline irrigation regime (3000 ppm) on tomato crop and soil. The results of two seasons experiments showed that saline irrigation significantly reduced tomato crop yield by an average reduction ratio of 51%, and biochar addition could not compensate such reduction. Furthermore, biochar did not reduce accumulated Na+ in fruits or roots. Tomato fruits produced from biochar-added soil were lower in TSS levels (41.7% reduction ratio) yet larger in diameter by approximately 1.5-fold increase. Interestingly, biochar addition into soil greatly promotes the length of stem-borne lateral roots and elevates the expression of LeNR (encodes nitrate reductase enzyme) in leaves yet under fresh irrigation regime. For soil properties, biochar application enhanced the soil properties under either saline or fresh water irrigation conditions. Collectively, it is assumed that biochar application to fertile soil in Nile Valley of Egypt could not alleviate tomato fruits yield reduction affected by applied saline irrigation regime. [ABSTRACT FROM AUTHOR]

Using livestock residues as alternative fertilizers is a sustainable practice which recycles nutrients that would otherwise be lost. However, organic fertilizers may have a large impact on N2O emissions, offsetting the beneficial effects of C sequestration. After four years from biochar application, greenhouse gas fluxes were monitored for two years from a Maize field fertilized with digestate, slurry, or urea, with and without biochar. The objectives of the present study were to assess (i) the climate feedback of using residues from the livestock chain as alternative fertilizers and (ii) the contribution of biochar in mitigating GHGs emissions, while increasing the organic C in soil. Digestate was shown to have the highest impact on CO2 and N2O emissions from soil, with respect to mineral fertilization (+29 and +142%), more than slurry (+21 and −5%), whereas both residues positively affected CH4 uptake (+5 and +14%, respectively). The maximum N2O peaks occurred between 7–20 days after fertilization, accounting for 61% of total emissions, on average. Biochar was effective in reducing N2O emissions derived from mineral fertilization and digestate (−54% and −17%, respectively). An excess of labile organic matter and N induced the highest CO2 emissions and N2O peaks, independent of—or even triggered by—biochar. Mitigation of GHG emissions, from soils fertilized with livestock chain residue, can be obtained using biochar, but with limitations dependent on (i) the quantity of organic matter added, (ii) its quality, and (iii) the time from application: those aspects that deserve further investigations. [ABSTRACT FROM AUTHOR]

The effective use of digestate as exogenous organic matter to enhance soil carbon sequestration depends on the balance between labile and recalcitrant organic carbon, which is influenced by the type of feedstock, the fermentation process, and the fraction (liquid, solid) of the fermented product used. In this work, in order to change the ratio of labile to stable carbon in the resulting fertiliser, the digestate was mixed with organic carbon-rich supplements: biochar and Humac (a humic acid-rich substance). The pot experiment was carried out under controlled conditions with maize (Zea mays L.) in soil amended with the digestate (D), which was incubated with Humac (H), biochar (B), or a combination of both (D + B + H) before the application. Digestate enriched with Humac showed improved short-term nutrient (carbon, phosphorus, nitrogen) transformation, as indicated by soil enzyme activity and the highest maize biomass production of. Total carbon content, C:N ratio, short-term respiration activity, and nitrification were most enhanced by digestate enriched with either biochar or combined biochar + Humac). Long-term nitrogen mineralization was mostly enhanced by digestate + Humac, as indicated by amino-acid-induced respiration and urease activity. Short-term positive effects of digestate + biochar (eventually + Humac) on catabolism were proven, whereas their long-term effects on nutrient mineralization were negative (i.e., biochar-mediated immobilization, sequestration), which should be the focus of further research in future. [ABSTRACT FROM AUTHOR]

Biochar amendments have been widely used in agricultural soil for lowering N2O and NO emissions while improving soil fertility and crop performance. However, a thorough understanding of the longevity of the favorable effects would be a prerequisite for large-scale biochar application in agriculture. We conducted a three-year greenhouse vegetable trial in Southeast China to systematically investigate the impacts of biochar mixed with nitrogen (N) on soil N2O and NO emissions, vegetable performance, and soil fertility at an interannual scale. The field experiment was established in November 2016 with biochar (0, 20 and 40 t ha−1; C0, C1, and C2, respectively), applied once without/with 240 kg N ha−1 urea (N0 or N1, respectively). Soil N2O and NO emissions were monitored during the spring vegetable cultivation period, and vegetable yield, quality, and soil properties were measured after harvests in 2018, 2019, and 2020. Results indicated that N application significantly increased N2O and NO emissions and vegetable yield throughout the trial period. Biochar combined with N generally reduced N2O and NO emissions and emission factors while increasing the vegetable yield, leading to lower yield-scaled N2O and NO emissions in 2018 and 2019. Biochar markedly enhanced soil pH and organic carbon and persisted, but generally had no significant effect on N use efficiency (NUE), vegetable quality, and soil fertility index (SFI) among treatments in over-fertilized vegetable fields. Based on our results, biochar application at 20 t ha−1 combined with N seemed to achieve the highest agronomic and environmental benefits for intensive vegetable production in Southeast China. [ABSTRACT FROM AUTHOR]

A serious acidification trend currently affects paddy soil and soil phosphorus (P) availability has declined in rice production. This study investigated the effect of rice-straw biochar on P availability and the adaptability of rice roots in acidified soil. Rice was grown in rhizoboxes, allowing for the precise sampling of rhizosphere and bulk soil for the sequential extraction of P fractions. Biochar may provide a liming effect and strong nutrient adsorption, leading to soil improvement. The results confirmed that biochar application significantly improved plant growth and P accumulation in shoots by 29% and 75%, respectively. However, the application of washed biochar and equivalent lime only increased shoot biomass and P accumulation by 13.4% and 11.2%, and by 42% and 38%, respectively. Compared with the control, applying biochar increased the plant-available P component contents in rhizosphere and bulk soil. Biochar affected the chemical balance among the different P fractions, increased aluminum-bound phosphate (Al-P) pool, calcium-bound phosphate (Ca-P) pool and decreased the occluded phosphate pool in acidic paddy soil. Biochar amendment significantly improved root growth of and increased the citrate exudation from roots under low P supply, accompanied by the enhanced expression of the anion-transporter-related OsFRDL4 gene and the OsPT1 phosphate transporter. The results showed that biochar application in degraded acidic soils could improve rice potential for P acquisition to increase available P component and maintain high citrate exudation. [ABSTRACT FROM AUTHOR]

Biochar (BC) is often proposed as a tool for climate change mitigation, due to the expected long lifetime in the environment. However, BC's stability can vary depending on feedstock type and the presence of labile carbon fractions. In this study, we verify the recent methods with new possible tools for biochar stability assessment on six different biochars derived from commonly available Europe biomass sources. Elemental composition (CHNO), dissolved organic carbon (DOC) and water-soluble carbonates content (WSC), volatile organic compounds (VOCs) composition, and mid-infrared spectra (MIR) were performed to estimate the persistence of biochars. Under similar conditions of pyrolysis, biochar properties can vary depending on a feedstock origin. Less aromatic structure and higher contents of labile carbon fractions (DOCs and WSC) in food waste biochars affected the lower stability, while biochars derived from high lignocellulose materials (straw, wood, and grass) were strongly carbonized, with persistent, aromatic structure. Labile carbon pool content (DOC, WSC) and spectral analysis can be useful tools for biochar stability assessment, giving similar information to the standard molar ratio method. Biochars obtained from agriculture and forestry management biomass should be considered as highly stable in soil and are appropriate for long-term carbon sequestration purposes. [ABSTRACT FROM AUTHOR]

Continuous cropping obstacles limit soybean production. Biochar is beneficial for soybean growth, but it is unclear whether biochar performs a sustainable role in continuous cropping. To further explore the effects of biochar on soil properties and soybean growth, a ceramic Wagner pot-simulated field experiment was conducted with biochar at different doses (12, 24, and 48 t·ha−1) over a period of 3 years, no fertilizer, no biochar (CK) and fertilizer (F)treatments were used for comparison. The results showed that biochar significantly reduced soil bulk and improved the rhizosphere soil pH, available nutrients (N, K), and total nutrients (C, N, P, and K) compared with CK and F. Moreover, the soybean root length, surface area, volume, and exudates increased with biochar amendment. In particular, biochar significantly increased the nodule number, dry weight, and nitrogenase activity of soybean. Furthermore, biochar promoted soybean growth and increased soybean yield. In general, we found that the soybean yield increased with biochar and that biochar had a positive, sustainable effect on soil properties and soybean root growth, providing a new cultivation measure for soil health and soybean production in continuous cropping, which is very important for increasing soybean productivity to break the limitations of soybean traditional continuous cultivation. [ABSTRACT FROM AUTHOR]

Desertified land covers one-fourth of the world's total land area. Meeting the high food demands in areas affected by desertification is a major problem. This case study provided fundamental information to demonstrate the potential for utilizing the desertified land. The soybean trial was established in two sandy clay loam soils (desertified land) and one silty clay loam soil. Two types of biochar were applied as treatments. We aimed to investigate the response of soybean plants to soil structure, soil nutrient condition, and biochar amendment in the two types of soil. In addition, ridge regression was employed to model the plant growth indicators by soil structure, soil nutrients condition, soil water content, and biochar amendment. We conclude that (1) overall soil productivity in sandy clay loam soil is lower than in silty clay loam soil. The sandy clay loam soil may have high efficacy for crop production due to its higher harvest index. (2) Aggregate size 0.5–1 mm, 1–2 mm, and 2–3 mm indicated more important in plant biomass formation in silty clay loam soil. The low aggregate stability of sandy clay loam soil made the field more vulnerable to wind erosion in the semi-arid monsoon climate. (3) Cob biochar and wood biochar increased soybean shoot biomass by 48.7% and 45.0% in silty clay loam soil. (4) The higher N-fixing ability of nodules in sandy clay loam soil indicates an advantage to reduce the use of N-fertilizers in desertified areas. (5) Exponential polynomial regression ameliorated the accuracy of prediction of plant growth indicators in comparison to linear regression. [ABSTRACT FROM AUTHOR]

One of the challenges of harnessing higher productivity levels and sustainability of agriculture related to N fertilization is in expanding soil N2O emissions, which has become a serious issue in recent years. Recent studies suggest that biochar may be the solution to this problem, but there is still a knowledge gap related to biochar application rates and its reapplication in Central Europe; therefore, in this study, we investigated the effect of biochar (initial application and reapplication in 2014 and 2018, respectively, at rates of 0, 10 and 20 t ha−1) combined with N-fertilizer (N0—0 kg N ha−1; N1—108 kg N ha−1 and N2—162 kg N ha−1) during the growing season of maize in 2019 (warm temperature with normal precipitation) on the changes of soil properties and N2O emissions in the silty loam, Haplic Luvisol, in the temperate climate of Slovakia. The results showed that the application and reapplication of biochar proved to be an excellent tool for increasing soil pH (in the range 7–13%), soil organic carbon—Corg (2–212%), and reducing the soil's NH4+ (41–69%); however, there were more pronounced positive effects when biochar was combined with N-fertilizer at the higher level (N2). The same effects were found in the case of N2O emissions (reduction in the range 33–83%). Biochar applied without N-fertilizer and combined with the higher fertilizer level had a suppressive effect on N2O emissions. Biochar did not have any effect on maize yield in 2019. [ABSTRACT FROM AUTHOR]

Dry direct-seeded rice (dry-DSR) is an efficient, resource-saving and environmentally friendly cropping system. The employment of water-saving and drought-resistant rice (WDR) for dry direct-seeding can better meet the needs of dry-direct seeding systems. However, the decline in seedling emergence rate and poor seedling growth are the main bottlenecks under current direct-seeded rice production. Seed treatment is a sustainable and effective technique to overcome these issues. Therefore, growth chamber and field experiments were conducted to assess the impact of poplar wood vinegar (WV) priming and rice straw biochar (BC) coating on emergence, establishment, growth, physio-biochemical events, and ultimate yield. We treated the seeds of WDR viz., Hanyou 73 with WV, BC, and co-treatment WV + BC. The results showed that seed priming with 1:50 WV concentration and coating with 20% BC content was the optimal ratio for promoting germination and seedling growth. The field evaluation indicated that individual WV and BC markedly promoted the final emergence by 58% and 31%, respectively, while co-treatment WV + BC increased by 67%. Likewise, WV and BC significantly enhanced total seedling biomass by 26% and 10%, respectively, and the respective enhancement of WV + BC was 31%. For ultimate yield, WV and BC produced 12% and 19% higher grain yield, respectively, whereas WV + BC yielded 20%. The above results revealed that WV and WV + BC were the most effective treatment. Our findings may provide new avenues for advancing pre-sowing seed treatments facilitating the stand establishment and grain yield of dry direct-seeded rice. [ABSTRACT FROM AUTHOR]

Global climatic change leads to many detrimental effects on all life forms. Outstanding case, salinity, and drought are considered multidimensional stress that severely affect plant growth and sustainable agriculture. Thymus vulgaris is a medicinal plant that has phytochemical constituents, and it is threatened by several abiotic stresses caused by climate change. Therefore, the present study aims to evaluate the physiological response and thyme tolerance grown on a newlyreclaimed saline sandy soil under drought conditions and treated by biochar-loaded biofertilizers, nano-zeolite, and nano-silicon through two consecutive seasons. The nanoparticles enhanced plant growth and alleviated the adverse effect of drought. Additionally, a synergistic effect was noticed when combining nanoparticles and biofertilizers. The quadruple combined treatment of nano-zeolite, nano-silicon, biochar, and organic matter (T7) significantly increased thyme morphological traits, photosynthetic parameters, oil, and yield compared to control treatment. Additionally, T7 increased the concentration of endogenous nutrients (N, P, K, Na, Ca, Mg, Zn, Fe, Mn), proline, total phenols, and total flavonoids, in addition to indoleacetic acid, gibberellic acid, and antioxidant enzymes in thyme compared to other treatments. T7 showed the lowest concentration of soluble sugars, abscisic acid, and transpiration rate. Interestingly, T7 increased the medicinal benefits of thyme by increasing its vital hydrocarbons, and oxygenated compounds. These findings introduce a dual benefit of nano-fertilizers in combination with biochar and organic matter in ameliorating soil salinity and drought along with increasing thymegrowth, productivity, and therapeutic value. [ABSTRACT FROM AUTHOR]

The objective of this study was to explore the effects of plant growth-promoting rhizobacteria (PGPR), strain Bacillus licheniformis, with softwood biochar amendment on potato growth and water use efficiency (WUE) under a deficit irrigation (DI) regime. A pot experiment was conducted in a greenhouse. The results showed that PGPR improved leaf gas exchange rates, including photosynthesis rate, stomatal conductance and transpiration rate at early seedling stage, while tended to depress these parameters gradually until final harvest. The effects of biochar on plant leaf physiology, plant growth and WUE were not evident. Plants were more affected by DI than PGPR inoculation and biochar amendment. DI significantly decreased leaf gas exchange rates after exposure to water treatment for around three weeks, and the negative effect was eliminated at final harvest. At final harvest, DI significantly decreased leaf area, specific leaf area, dry mass of leaf and stem, total dry mass, dry mass increment and plant water use. The synergistical effect of PGPR strain Bacillus licheniformis and DI on plant growth and WUE were not observed in our study. WUE was solely improved by DI, indicating that, compared to PGPR inoculation, DI was a more effective measure to enhance plant WUE. [ABSTRACT FROM AUTHOR]

Biochar adsorption and microbial remediation have great potential in the field of soil remediation, but since both are stressed by high concentrations of toxic heavy metals when applied alone, combining the two may become an effective remediation method. In this study, the application effect of phosphorus-solubilizing bacteria (PSB) combined with rice husk biochar on the remediation of Pb/Cd-mixed pollution and the form differences of toxic metal were studied qualitatively and quantitatively. Compared with the contaminated soil, the combined remediation of biochar and PSB significantly increased the pH, carbon and phosphorus by 9.0%, 299.4% and 157.0%. Meanwhile, combined remediation increased the total microbial, bacterial and fungal biomass by 92.11%, 103.13% and 138.10%. This confirmed that the addition of biochar increased the soil nutrients and provided good conditions for PSB or native microorganisms to flourish. The extraction results showed that the stable form of Pb/Cd with biochar + PSB was better than that with biochar/PSB alone. Combined remediation significantly increased the acid-soluble and non-bioavailable fraction of Pb/Cd by 5/15 times and 14/5.8 times in contaminated soil. The acid-soluble and non-bioavailable fractions are the main fraction of toxic metals after combined remediation (>80%). The acid-soluble and non-bioavailable fractions were mainly carbonates and phosphate-based Pb/Cd minerals (XRD analysis). PCA and a GWB model further confirmed that the release of pH and phosphorus was the key to the passivation of Pb/Cd in a short time. Meanwhile, the combination of the biochar (phosphorus supply guarantee) and PSB (acid-soluble phosphorus function) can reduce soil acidification and improve soil nutrients, thus increasing microbial abundance in contaminated soil, even more than that in non-contaminated soil. [ABSTRACT FROM AUTHOR]

Biochemical methane potential (BMP) tests were conducted for investigating the effects of alfalfa-derived biochar (AF-BC) on anaerobic digestion (AD) of dairy manure under various loading of AF-BC (0–10 g/L). BMP tests were performed at mesophilic temperature (37 °C) with the addition of AF-BC. Biogas and methane volumes and concentrations, water quality parameters (i.e., COD (chemical oxygen demand)), and volatile fatty acids (VFAs) were measured during the AD process. The addition of 1 and 5 g/L of AF-BC increased the biogas yields by 15.51% and 26.09% and methane yields by 14.61% and 26.88% compared with the control without addition of AF-BC. Additionally, the addition of AF-BC (1–10 g/L) decreased the lag phase by 7.14–22.45% and the CO2 content of biogas by 13.60–32.48%, while increasing the COD removal efficiency by 19.19–35.94% in the AD of dairy manure. Moreover, the addition of AF-BC also decreased total VFAs and acetic acid concentrations in the AD process. The increase in AD performance was mainly owing to the improvement of buffering ability of the AD system and direct interspecies electron transfer (DIET) among AD microorganisms resulting from the addition of AF-BC. In contrast, the addition of 10 g/L AF-BC did not show any obvious improvement in biogas and methane yields in the AD of dairy manure, possibly because of toxic effects from excessive addition of AF-BC toward the AD microorganisms. Therefore, this study supported practical feasibility of AF-BC-enhanced AD of dairy manure. [ABSTRACT FROM AUTHOR]

Industrial wastes and agricultural byproducts are increasingly used in crop production as fertilizers, but their impacts on soil carbon (C) sequestration remain poorly understood. The aim of this study was to examine the effects of applying steel slag (SS), biochar (B), and a combination of these two materials (SS + B) on total soil organic C (SOC), active SOC fractions, and C pool management index (CPMI) in a subtropical paddy field in China. The treatments were applied at a rate of 8 t ha-1 to rice at the two (early and late) crop seasons in 2015. The SOC concentrations in the top 30 cm soils in the SS + B treatments were 28.7% and 42.2% higher in the early and late crops, respectively, as compared to the controls (p < 0.05). SOC was positively correlated with soil C:N ratio across the two crop seasons (r = 0.92-0.97, p < 0.01). As compared to the control, SS + B treatment had significantly higher carbon pool index (CPI) in both early (22.4%) and late (40.1%) crops. In the early crop, the C pool activity index (CPAI) was significantly lower in B and SS + B treatments by over 50% than in the control, while the soil C pool management index (CPMI) in the SS, B, and SS + B treatments was lower than that in the control by 36.7%, 41.6%, and 45.4%, respectively. In contrast, in the late crop, no significant differences in CPAI and CPMI were observed among the treatments. Our findings suggest that the addition of steel slag and biochar in subtropical paddy fields could decrease active SOC pools and enhance soil C sequestration only in the early crop, but not the late crop. [ABSTRACT FROM AUTHOR]