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Soil with heavy metals contamination, mainly lead (Pb), cadmium (Cd), and chromium (Cr) is a progressively worldwide alarming environmental problem. Recently, biochar has been used as a soil amendment to remediate contaminated soils, but little work has been done to compare with other organic amendments like compost. We investigated biochar and compost's comparative effect on Pb, Cd, and Cr immobilization in soil, photosynthesis, and growth of maize plants. Ten kg soil was placed in pots and were spiked with Pb, Cd, and Cr at concentrations 20, 10, 20 mg kg −1 . The biochar and compost treatments included 0, 0.5, 1, 2, and 4% were separately applied to the soil. The crop from pots was harvested after 60 days. The results show that the highest reduction of AB-DTPA extractable Pb, Cd, and Cr in soil was 79%, 61% and 78% with 4% biochar, followed by 61%, 43% and 60% with 4% compost compared to the control, respectively. Similarly, the highest reduction in shoot Pb, Cd, and Cr concentration was 71%, 63% and 78%with 4% biochar, followed by 50%, 50% and 71% with 4% compost than the control, respectively. The maximum increase in shoot and dry root weight, total chlorophyll contents, and gas exchange characteristics were recorded with 4% biochar, followed by 4% compost than the control. The maximum increase in soil organic matter and total nitrogen (N) was recorded at 4% biochar application while available phosphorus and potassium in the soil at 4% compost application. It is concluded that both biochar and compost decreased heavy metals availability in the soil, reducing toxicity in the plant. However, biochar was most effective in reducing heavy metals content in soil and plant compared to compost. In the future, more low-cost, eco-friendly soil remediation methods should be developed for better soil health and plant productivity.

Farmers are not growing diversified crops and applying huge amounts of agrochemicals and imbalanced fertilizers in the rice-wheat cropping system (RWCS), since the 1960s. The objective of this study was to evaluate the microbial and nutrient dynamics in Indian mustard ( Brassica juncea L. ) under various sowing environments and nutrient sources during Rabi season (October–March), 2015–2016. The experiment was laid out in the split-plot design with three sowing dates in main-plots, and eight nutrient sources in sub-plots. The maximum bacteria, fungi, and actinomycetes population, soil microbial biomass carbon (SMBC), dehydrogenase activities, and available nitrogen, phosphorus, potassium, and sulphur (NPKS) were recorded on November 17 sown crop, and the lowest was observed on December 7 sowing during both the years, and in the pooled analysis. Furthermore, applied nutrient sources, highest bacteria, fungi, and actinomycetes population, available NPKS, SMBC, and dehydrogenase activity were observed in 75% recommended dose of fertilizers (RDF) + 25% N through pressmud (PM) +  Azotobacto  +  phosphorus solubilizing bacteria (PSB) than other nutrient sources. In conclusion, high demand and cost of chemical fertilizers can be replaced by 25% amount easily and locally available organic manures like PM compost to sustain the soil health and crop productivity. It will be helpful to restore the soil biodiversity in the RWCS and provide a roadmap for the researchers, government planners, and policymakers for the use of PM as a source of organic matter and nutrients.

Conventional agricultural practices and rising energy crisis create a question about the sustainability of the present-day food production system. Nutrient exhaustive crops can have a severe impact on native soil fertility by causing nutrient mining. In this backdrop, we conducted a comprehensive assessment of bio-priming intervention in red cabbage production considering nutrient uptake, the annual change in soil fertility, nutrient use efficiency, energy budgeting, and economic benefits for its sustainable intensification, among resource-poor farmers of Middle Gangetic Plains. The compatible microbial agents used in the study include Trichoderma harzianum , Pseudomonas fluorescens , and Bacillus subtilis . Field assays (2016–2017 and 2017–2018) of the present study revealed supplementing 75% of recommended NPK fertilizer with dual inoculation of T . harzianum and P . fluorescens increased macronutrient uptake (N, P, and K), root length, heading percentage, head diameter, head weight, and the total weight of red cabbage along with a positive annual change in soil organic carbon. Maximum positive annual change in available N and available P was recorded under 75% RDF +  P . fluorescens  +  B . subtilis and 75% RDF +  T . harzianum  +  B . subtilis , respectively. Bio-primed plants were also higher in terms of growth and nutrient use efficiency (agronomic efficiency, physiological efficiency, apparent recovery efficiency, partial factor productivity). Energy output (26,370 and 26,630 MJ ha −1 ), energy balance (13,643 and 13,903 MJ ha −1 ), maximum gross return (US $ 16,030 and 13,877 ha −1 ), and net return (US $ 15,966 and 13,813 ha −1 ) were considerably higher in T . harzianum, and P . fluorescens treated plants. The results suggest the significance of the bio-priming approach under existing integrated nutrient management strategies and the role of dual inoculations in producing synergistic effects on plant growth and maintaining the soil, food, and energy nexus.

Zinc (Zn) deficiency can severely inhibit plant growth, yield, and enzymatic activities. Zn plays a vital role in various enzymatic activities in plants. Arbuscular mycorrhizal fungi (AMF) play a crucial role in improving the plant’s Zn nutrition and mitigating Zn stress effects on plants. The current study was conducted to compare the response of inoculated and non-inoculated maize (YH 1898) in the presence of different levels of zinc under greenhouse conditions under a Zn deficient condition. There were two mycorrhizal levels (i.e., M + with mycorrhizae, M- without mycorrhizae) and five Zn levels (i.e., 0, 1.5, 3, 6, and 12 mg kg -1 ), with three replicates following completely randomized design. At the vegetative stage (before tillering), biochemical, physiological, and agronomic attributes were measured. The results showed that maize plants previously inoculated with AMF had higher gaseous exchange traits, i.e., a higher stomatal conductance rate, favoring an increased photosynthetic rate. Improvement in antioxidant enzyme activity was also observed in inoculated compared to non-inoculated maize plants. Moreover, AMF inoculation also played a beneficial role in nutrients availability and its uptake by plants. Higher Zn12 (12 mg Zn kg -1 soil) treatment accumulated a higher Zn concentration in soil, root, and shoot in AMF-inoculated than in non-inoculated maize plants. These results are consistent with mycorrhizal symbiosis beneficial role for maize physiological functioning in Zn deficient soil conditions. Additionally, AMF inoculation mitigated the stress conditions and assisted nutrient uptake by maize.

Consumption of heavy metals, especially lead (Pb) contaminated food is a serious threat to human health. Higher Pb uptake by the plant affects the quality, growth and yield of crops. However, inoculation of plant growth-promoting rhizobacteria (PGPR) along with a mixture of organic amendments and biochar could be an effective way to overcome the problem of Pb toxicity. That’s why current pot experiment was conducted to investigate the effect of compost mixed biochar (CB) and ACC deaminase producing PGPR on growth and yield of spinach plants under artificially induced Pb toxicity. Six different treatments i.e., control, Alcaligenes faecalis (PGPR1), Bacillus amyloliquefaciens (PGPR2), compost + biochar (CB), PGPR1 + CB and PGPR2 + CB were applied under 250 mg Pb kg -1 soil. Results showed that inoculation of PGPRs ( Alcaligenes faecalis and Bacillus amyloliquefaciens ) alone and along with CB significantly enhanced root fresh (47%) and dry weight (31%), potassium concentration (11%) in the spinach plant. Whereas, CB +  Bacillus amyloliquefaciens significantly decreased (43%) the concentration of Pb in the spinach root over control. In conclusion, CB +  Bacillus amyloliquefaciens has the potential to mitigate the Pb induced toxicity in the spinach. The obtained result can be further used in the planning and execution of rhizobacteria and compost mixed biochar-based soil amendment.

An important source of the destructive greenhouse gas, nitrous oxide (N 2 O) comes from the use of ammonium based nitrogen (N) fertilizers that release N 2 O in the incomplete conversion (nitrification) of NH 4 +  to NO 3 ˉ 1 . Biochar has been shown to decrease nitrification rates and N 2 O emission. However, there is little information from semi-arid environments such as in Pakistan where conditions favor N 2 O emissions. Therefore, the object was to conduct field experiment to determine the impact of biochar rates in the presence or absence of urea amended soils on yield-scaled N 2 O emissions, and wheat yield and N use efficiency (NUE). The experiment on wheat ( Triticum aestivum L.), had a randomized complete block design with four replications and the treatments: control, sole urea (150 kg N ha −1 ), 5 Mg biochar ha −1 (B5), 10 Mg biochar ha −1 (B10), urea + B5 or urea + B10. In urea amended soils with B5 or B10 treatments, biochar reduced total N 2 O emissions by 27 and 35%, respectively, over the sole urea treatment. Urea + B5 or + B10 treatments had 34 and 46% lower levels, respectively, of yield scaled N 2 O over the sole urea treatment. The B5 and B10 treatments had 24–38%, 9–13%, 12–27% and 35–43%, respectively greater wheat above-ground biomass, grain yield, total N uptake, and NUE, over sole urea. The biochar treatments increased the retention of NH 4 +  which likely was an important mechanism for reducing N 2 O by limiting nitrification. These results indicate that amending soils with biochar has potential to mitigate N 2 O emissions in a semi-arid and at the same time increase wheat productivity.

High lead (Pb) concentration in soils is becoming a severe threat to human health. It also deteriorates plants, growth, yield and quality of food. Although the use of plant growth-promoting rhizobacteria (PGPR), biochar and compost can be effective environment-friendly amendments for decreasing Pb stress in crop plants, the impacts of their simultaneous co-application has not been well documented. Thus current study was carried, was conducted to investigate the role of rhizobacteria and compost mixed biochar (CB) under Pb stress on selected soil properties and agronomic parameters in mint ( Mentha piperita L.) plants. To this end, six treatments were studied: Alcaligenes faecalis , Bacillus amyloliquefaciens , CB, PGPR1 + CB, PGPR2 + CB and control. Results showed that the application A. faecalis  + CB significantly decreased soil pH and EC over control. However, OM, nitrogen, phosphorus and potassium concentration were significantly improved in the soil where A. faecalis  + CB was applied over control. The A. faecalis  + CB treatment significantly improved mint plant root dry weight (58%), leaves dry weight (32%), chlorophyll (37%), and N (46%), P (39%) and K (63%) leave concentration, while also decreasing the leaves Pb uptake by 13.5% when compared to the unamended control. In conclusion, A. faecalis  + CB has a greater potential to improve overall soil quality, fertility and mint plant productivity under high Pb soil concentration compared to the sole application of CB and A. faecalis .

Drought stress can have negative impacts on crop productivity. It triggers the accumulation of reactive oxygen species, which causes oxidative stress. Limited water and nutrient uptake under drought stress also decreases plant growth. Using cobalt and fulvic acid with biochar in such scenarios can effectively promote plant growth. Cobalt (Co) is a component of various enzymes and co-enzymes. It can increase the concentration of flavonoids, total phenols, antioxidant enzymes (peroxidase, catalase, and polyphenol oxidase) and proline. Fulvic acid (FA), a constituent of soil organic matter, increases the accessibility of nutrients to plants. Biochar (BC) can enhance soil moisture retention, nutrient uptake, and plant productivity during drought stress. That’s why the current study explored the influence of Co, FA and BC on chili plants under drought stress. This study involved 8 treatments, i.e., control, 4 g/L fulvic acid (4FA), 20 mg/L cobalt sulfate (20CoSO 4 ), 4FA + 20CoSO 4 , 0.50%MFWBC (0.50 MFWBC), 4FA + 0.50MFWBC, 20CoSO 4  + 0.50MFWBC, 4FA + 20CoSO 4  + 0.50MFWBC. Results showed that 4 g/L FA + 20CoSO 4 with 0.50MFWBC caused an increase in chili plant height (23.29%), plant dry weight (28.85%), fruit length (20.17%), fruit girth (21.41%) and fruit yield (25.13%) compared to control. The effectiveness of 4 g/L FA + 20CoSO 4 with 0.50MFWBC was also confirmed by a significant increase in total chlorophyll contents, as well as nitrogen (N), phosphorus (P), and potassium (K) in leaves over control. In conclusion4g/L, FA + 20CoSO 4 with 0.50MFWBC can potentially improve the growth of chili cultivated in drought stress. It is suggested that 4 g/L FA + 20CoSO 4 with 0.50MFWBC be used to alleviate drought stress in chili plants.

Lignin is a major component of soil organic matter and also a rich source of carbon dioxide in soils. However, because of its complex structure and recalcitrant nature, lignin degradation is a major challenge. Efforts have been made from time to time to understand the lignin polymeric structure better and develop simpler, economical, and bio-friendly methods of degradation. Certain enzymes from specialized bacteria and fungi have been identified by researchers that can metabolize lignin and enable utilization of lignin-derived carbon sources. In this review, we attempt to provide an overview of the complexity of lignin’s polymeric structure, its distribution in forest soils, and its chemical nature. Herein, we focus on lignin biodegradation by various microorganism, fungi and bacteria present in plant biomass and soils that are capable of producing ligninolytic enzymes such as lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), and dye-decolorizing peroxidase (DyP). The relevant and recent reports have been included in this review.

In this study, we explored the role of biochar (BC) and/or urease inhibitor (UI) in mitigating ammonia (NH 3 ) and nitrous oxide (N 2 O) discharge from urea fertilized wheat cultivated fields in Pakistan (34.01°N, 71.71°E). The experiment included five treatments [control, urea (150 kg N ha −1 ), BC (10 Mg ha −1 ), urea + BC and urea + BC + UI (1 L ton −1 )], which were all repeated four times and were carried out in a randomized complete block design. Urea supplementation along with BC and BC + UI reduced soil NH 3 emissions by 27% and 69%, respectively, compared to sole urea application. Nitrous oxide emissions from urea fertilized plots were also reduced by 24% and 53% applying BC and BC + UI, respectively, compared to urea alone. Application of BC with urea improved the grain yield, shoot biomass, and total N uptake of wheat by 13%, 24%, and 12%, respectively, compared to urea alone. Moreover, UI further promoted biomass and grain yield, and N assimilation in wheat by 38%, 22% and 27%, respectively, over sole urea application. In conclusion, application of BC and/or UI can mitigate NH 3 and N 2 O emissions from urea fertilized soil, improve N use efficiency (NUE) and overall crop productivity.