1 Introduction

Biochar, also known as "black carbon" (Singh and Kumar 2020), is a solid byproduct of biomass pyrolysis that is created when carbon-rich materials are heated to high temperatures in an oxygen-deficient atmosphere. Numerous soil properties, including pH, microbial diversity and community structure, GHG emission, nutrient retention, and soil physical structure, may be changed when biochar is applied to the soil, according to extensive research on the subject over the past few years (Singh and Kumar 2020). Biochar can be used for a number of processes, including wastewater treatment (Shaheen et al. 2019), crop disease management (Ahmed et al. 2022), immobilization of contaminants (Shen et al. 2019), enhancement of soil fertility (Arif et al. 2020) since it does have a well-developed porous structure (Leng et al. 2021), a large number of inorganic nutrients (Dai et al. 2020), a large number of functional groups and excellent stability of carbon (Wang et al. 2020b).

Global population growth is a challenge to food supply, which is made worse by climate change, ongoing pest and disease outbreaks, and poor crop productivity due to the hurdles in identifying diseases in plants, particularly those are caused by the soil borne pathogens (Ghorbanpour et al. 2018). Some of these plant pathogens found in soil include fungi, oomycetes, bacteria, viruses, and nematodes, with fungi being the most common category to infect and harm roots (Montiel-Rozas et al. 2019). Since soil-borne diseases share some traits in common and affect both abiotic and biotic components, therefore, the management of such infections seems challenging (Liu et al. 2020).

Synthetic pesticides have become the first and foremost strategies for preventing outbreaks of pests and diseases in agriculture, but their careless use has exacerbated environmental issues and impacted the environment and at last human health negatively. Biological control has been around for a while, recorded for certain good management of soil borne diseases but could not attract as much attention as chemicals. Species of many fungi and bacteria for example Trichoderma, Beauveria, Metarhizium, Pseudomonas, Bacillus etc. has recently gained increase in application against soil borne diseases as they have shown antagonistic potential, making it one of the alternative methods for disease eradication (Zin and Badaluddin 2020).

In the past few years, a new low cost alternative of chemicals “Biochar” has emerged and gained a lot of attention for reclamation of soil and management of soil borne diseases (Silva et al. 2021). Lima et al. (2018) and Medeiros et al. (2020) researched using biochar and stated that biochar enhances the physical, chemical, and biological characteristics of the soil in addition to improving water and nutrient retention, promoting carbon sequestration, enhancing beneficial soil microbes and controlling soil-borne plant pathogens. The objective of this review is to emphasize the application of biochar in soil, particularly focusing on managing soil-borne plant pathogens. This involves biochar's primary action of enhancing soil health and its secondary action of exhibiting antimicrobial activities against plant pathogens (Lehmann and Joseph 2015; Joseph et al. 2019).

1.1 Composition and Making of Biochar

Biomass is being converted to biochar as a result of growing interest in using it for various applications. Thermochemical conversion is a typical method for making biochar. The methods of thermochemical conversion include torrefaction, gasification, hydrothermal carbonization, and pyrolysis. Biochar generates energy from crop waste, greenhouse waste, wood chips, and a variety of other wastes at temperatures ranging from 400 to 500°C in the absence of oxygen. In varying amounts; it is made up of CHO (carbon, hydrogen & oxygen), nitrogen (N), and ash (Elkhlifi et al. 2023).

Pyrolysis between 250-900°C decomposes organic molecules in an environment devoid of oxygen called ‘Thermal Decomposition’ (Zakaria et al. 2023). This method is an alternative method for turning waste biomass into products with added value like biochar, syngas, and bio-oil (Shi et al. 2022). The lignocellulosic ingredients, such as lignin, hemicellulose and cellulose, go through reaction processes 1. depolymerization, 2. fragmentation, and 3. cross-linking at a given temperature during the process, producing a variety of products in the form of solid, liquid, and gas (Pandit et al. 2023), (Fig. 1).

Fig. 1
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Biochar of different biomass for soil remediation. Biochar from different biomasses after pyrolysis at different temperatures ranging from 400 to 700°C helps remediating soils

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The methods used to characterize biochar are based on elemental analysis, surface functional groups, and structural analysis. The structural and elemental analysis of biochar facilitates predicting its environmental effects. These characteristics indicate that biochar is a top-rated absorbent that helps remove abiotic and biotic pollutants in bulk from soil (Wood et al. 2023). Understanding the impact of biochar pH on soil pH as well as other soil characteristics and processes is crucial. In the literature, biochar pH ranges from 3.1 to 12.0 (Lehmann 2007; Mukherjee et al. 2011).

1.2 Biochar Impact on Soil Physical Attributes

Addition of biochar encourages changes in the physical properties of the soil. As a result of enhanced soil physical structure and consequently better growing conditions for plants, biochar helps reduce bulk density (Blanco-Canqui 2017). The use of biochar encourages soil aeration, water infiltration, and soil compaction reduction, all of which boost soil's ability to hold water (Fig. 2). The use of biochar encourages soil aeration, water infiltration, and soil compaction reduction, all of which boost soil's ability to store water. (Razzaghi et al. 2020). Decreased bulk density of soil always improves soil’s physico-chemistry; increases field capacity, soil porosity, available water content and permanent wilting point (Edeh et al. 2020). Zhang and colleagues (2017) used rice straw biochar in managing Ralstonia solanacearum causing bacterial wilt in tobacco under field conditions. They used 3 ton ha-1 biochar which resulted in a reduction of 76.64% in the disease incidence (Tables 1, 2, 3).

Fig. 2
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Effect of biochar on the physical, chemical and biological properties of soil. Biochar enhances soil density, texture, porosity, permeability, pH, WHC & CFC values, nutrient availability and microbial population in the soil. Abbreviations used: CFC (Chlorofluorocarbon), WHC (Water Holding Capacity), pH (Potential of Hydrogen), SOM (Soil organic matter)

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Table 1 Biochar application improves biological properties of soil
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Table 2 Biochar application improves physical properties of soil
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Table 3 Biochar application improves chemical properties of soil
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1.3 Biochar Impact on Soil Chemistry

Neutralizing acidity and increasing cation exchange capacity (CEC) are useful features with the purpose of improving the soil chemistry and biochar gained significant interest as an amendment to serve this purpose (Brassard et al. 2016). Oxides, hydroxides and carbonates of calcium, magnesium and Potassium from biochar contribute to high pH whereas, functional groups COOH, OH, and alcoholic OH which are abundant on the surface interact with basic soil cations to boost acidic soils to buffer pH (Han et al. 2020).

The alkalinity of the biochar depends on the temperature during pyrolysis and the ingredients of the source. The capacity of biochar to absorb the cations Ca2+ and NH4+, which are vital to plants, is directly connected to its CEC. After eight years of research on the application of biochar to soil, Luo and colleagues (2020) reported an increase in soil organic carbon and total nitrogen. Zhou and colleagues (2017) discovered that biochar accelerates the levels of sodium nitrate (NaNO3), ammonium nitrate (NH4NO3), ammonium sulphate ([NH4]2SO4), and ammonium tartrate (C4H12N2O6), all of which are critical for nitrogen signaling and MAPK (Mitogen-Activated Protein Kinase) pathogenicity (Table 3).

1.4 Biochar Impact on Soil Water, pH and Nutrient Retention

One of the key areas of interest about biochar is its impact on soil water dynamics. Many researchers investigated that biochar reclaimed soil and improved water retention and availability, highlighting its ability to improve water holding capacity and reduce water loss through evaporation. Zhang et al. (2021) examined the impact of biochar on soil water retention in sandy soils and found that the addition of biochar significantly increased the water holding capacity of the soil by enhancing its ability to retain water. Biochar pores create microhabitats, retain moisture and provide a favorable environment for root growth and water uptake by plants. Liu and teammates (2022) investigated how biochar affected soil and water availability in clay soils. Their findings indicated that biochar amendment improved soil structure and increased water infiltration rates, resulting in enhanced water availability for plant uptake. The researchers observed that biochar facilitated the formation of stable aggregates, reducing soil compaction and increasing capacity in soil to hold and release water over time. A study by Wang et al. (2020a) explored that biochar affects soil evaporation; reduces evaporation rates by enhancing soil water retention. Hydrophobic properties of biochar which act as physical barriers, reduces water loss from the soil surface (Fig. 3).

Fig. 3
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General functional principles of biochar. Biochar used in different fields like Agricultures, Water, Climate & Energy for different purposes enhances soil fertility, carbon sequestration and decreases leaching of pesticides and nutrients, emission of methan and nitrous oxide

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The potential of biochar as a sustainable soil management strategy for improving water and nutrient retention, which could have significant implications for enhancing agricultural productivity and mitigating environmental impacts are discussed by Li et al. (2021). They stated that biochar amendment improved the cation exchange capacity of soil, leading to increased nutrient retention and reduced nutrient leaching. Findings concluded by Guo et al. (2020) highlighted biochar, a sustainable and eco-friendly solution for water and pH regulation in agricultural and environmental systems (Fig. 4). They confirmed that biochar enhanced pH buffering capacity in acidic soils, mitigating the negative effects of soil acidification and maintaining optimal pH conditions for plant growth (Guo et al. 2020).

Fig. 4
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Effect of biochar on soil pH. Biochar regulated pH in agricultural and environmental system. In low pH soil, biochar decreases the microbial biomass helps managing plant diseases by fungi and in high pH soil, biochar increases the microbial biomass of antagonistic microbes helps keep pathogenic microbes at their lower populations. Abbreviations used: As (Arsenic), Cd (Cadmium), CO2 (Carbon dioxide), C (Carbon), pH (Potential of Hydrogen)

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1.5 Biochar Impact on Greenhouse Gas Emissions and Carbon Sequestration

Being a carbon rich compound, biochar enhances carbon sequestration in soil and slows down climate change (Lehmann et al. 2006). In the biosphere, it has the ability to sequester carbon, as opposed to just storing it. Given the right economic and governmental tools, sequestration using presently accessible feedstock might occur at the gigatonnes (Gt) scale. Bioenergy co-products from pyrolysis have the potential to be more powerful than the carbon gain from burning. Therefore, using biochar seems the best possible alternative towards sustainable agriculture and environment includes direct inclusion of biomass, which causes quick and fast mineralization and CO2 release (Nolan et al. 2021) (Fig. 5).

Fig. 5
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Biochar effect on the carbon sequestration in soil. In plant ecosystem carbon emission caused after physiological activities of plants and microbial activities of soil microbes show negative effects on the plant shoots and roots and get released in the free environment. Biochar added in soil enhances carbon sequestration, releases different nutrients and makes available to the plants and increases soil fertility. Abbreviations used: Cu (Copper), P (Phosphorus), K (Potassium), Mg (Magnesium), Mn (Manganese), Fe (Iron), Zn (Zinc), pH (Potential of Hydrogen)

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Soil becomes the second largest carbon reservoir on the earth with a capacity of over 2500 Gt C (Lal 2010). Because of this, even little changes in soil carbon storage have a significant effect on the amount of C in the atmosphere and the rate of global warming (Smith 2012). According to UNFCCC, 2021 "4 per 1000" effort (4p1000) add an annual increase of 0.4% in soil carbon store help balancing annual rise in greenhouse gas emissions to improve environment and food security (Stockmann et al. 2013; Paustian et al. 2016, 2019; Zomer et al. 2017).

1.6 Biochar Impact on Carbon Neutrality

Biochar aids in achieving carbon neutrality due to its carbon-negative composition, CO2 sorption, and harmful priming effects (Wang et al. 2023). According to Denevan and colleagues, since long Indians were using biological wastes to produce black amazonian soils of high fertility; the idea was to turn the biological waste into highly fertile soils. As a green immobilization agent, it also showed the capacity to immobilize organic and heavy metal pollutants (Hou et al. 2022; Wang et al. 2022; Wang et al. 2021). In addition to its conventional use as a soil supplement to increase soil fertility and immobilize pollutants, biochar has also recently been used in non-soil applications that have shown to have great promise for reducing climate change (Bartoli et al. 2020; Bolan et al. 2021).

1.7 Biochar Impact on Soil Microbial Attributes

Position, composition and population of microbes are brought by the amount of the biochar present in the soil. Porosity and high specific surface area of biochar helps produce a healthy environment for high reproduction in microbes and plant growth (Wang et al. 2016a, b). Palansooriya et al. (2019a, b) studied that micropores, mesopores and macropores of biochar particles help creating a convenient environment for the growth of bacteria, mycorrhizal fungi, ectomycorrhizal fungi and, arbuscular mycorrhizal fungi. Increased population of antagonists place a great defense against pathogens (Han et al. 2020) and many other bacteria like Proteobacteria play a key role in carbon and sulfur cycling (Zhu et al. 2019a, b) and nitrogen fixation (Semida et al. 2019).

The area near the root zone called ‘rhizosphere’ is the home of soil microorganisms. Since plants root exudate some compounds, become food for microorganisms henceforth, enhances microbial populations multifold than that of bulk soil (without vegetation) (Haldar and Sengupta 2016). There has been several mechanisms behind the modification of rhizospheric chemistry by plant roots include (I) absorption and secretion of organic compounds (II) gaseous exchange linked to the root and rhizosphere microbial respiration and, (III) uptake or release of water and nutrients linked to the changes to the redox potential and uptake or extrusion of protons (Dotaniya and Meena 2015). Neuman and Römheld 2012 have said, biochar does have the potential to change physical characteristics like number and size of micropores, aggregate stability, and hydrophobicity into rhizospheric soil.

Numerous studies have found that the type of soil in which biochar has been used can affect the number and biomass of soil microorganisms as well as the usefulness of these organisms in plant root colonization (Table 4). Li and teammates 2018 noted that charcoal increased the number of microbes in soil as determined by their respiration activity. On the other hand, Chintala et al., (2014) discovered a detrimental effect of soil added biochar on microbial activity.

Table 4 Effect of Biochar on soil microbiota
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1.8 Biochar Impact on Plant Growth Regulation

In 2011, Jeffery and his team conducted a thorough investigation and discovered that adding biochar to the soil has had beneficial effects; addition of biochar to soil has a considerable impact on plant development and the colonization of roots by microorganisms, such as nematodes and mycorrhizal fungi (Table 5). They observed a 10 percent increase in agricultural productivity after biochar was added. Prendergast-Miller and colleagues (2014) added biochar to soil found biomass of the roots is enhanced in maize and barley. Biochar accelerates secondary growth in plant roots and root hairs grow more in number and length to intake more nutrients and water from soil, resulting in increased growth and yield (Lehmann et al. 2011; Jeffery et al. 2017). Agegnehu and teammates in 2016 and Shen and teammates in 2018 applied biochar and found that biochar favorably affects stem and leaf growth; probably due to increased translocation of water and nutrients and photosynthesis. The higher crop production brought about by the faster growth seen in soils modified with biochar makes it a viable sustainable option for agricultural productivity (Verwaaijen et al. 2017; Glaser and Lehr 2019).

Table 5 Effect of biochar in the rhizosphere of plants
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1.9 Application of Biochar in Plant Disease Management

Studies support that biochar contributes in managing diseases in plants especially which were caused by the soil borne pathogens (Medeiros et al. 2021). Biochar performs directly and or indirectly which suppress plant diseases via a number of mechanisms like (i) improving soil attributes help promote plant health by enhanced nutrient availability (ii) increase in the population of beneficial microorganisms that bring down the population of harmful microorganisms via competition, parasitism and antibiosis (iii) sorption of compounds by plants that are toxic to the plants pathogens (iv) induction of plant resistance by activating secondary metabolites after the resistance genes get activated and, (v) changes of abiotic conditions, pH, EC, CEC, temperature, moisture etc. provide different management mechanisms for disease suppression (Fig. 6).

Fig. 6
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Effect of Biochar on microbial population density. Biochar enhances root colonization, and accumulates VOCs affects physical, chemical and biological properties of soil and plant as well helps increase the population of beneficial microbes and decrease the population of phytopathogenic microbes. Abbreviations used: VOC (Volatile Organic Compounds), AMF (Arbuscular Mycorrhizal Fungi)

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1.10 Biochar Effect on Phytopathogenic Bacteria

The use of biochar has shown promise in the management of bacterial infections in plants. Porous composition and large surface area of biochar absorbs and holds a variety of substances, including pathogens and their metabolites. Biochar naturally has antibacterial characteristics, Rodriguez-Ramos et al. (2022), proved that addition of biochar effectively reduced the population of bacteria resulting in decreased incidence of disease in tomato crops. Other way, it has also been demonstrated that the presence of biochar in the soil has a positive impact on the makeup of the microbial community, encouraging the prevalence of good microorganisms that compete with harmful bacteria. Bacterial wilt by Ralstonia solanacearum is a devastating disease that affects a variety of plant species, including tomato, brinjal, potato, peanut and banana which seems most significant in retarding yield to the global production of these crops (Mansfield et al. 2012). Bacterium enters the plant through the roots and colonizes the xylem, causing the plants to completely wilt and die (Genin and Denny 2012). Bacterium can spread through water, rhizospheric contact, etc. and persists in the soil for a very long time in the absence of crops that are vulnerable to it, making its control exceedingly difficult (Van Stan et al. 2020). Biochar dramatically reduced bacterial wilt through altering the microbial composition and soil's chemical characteristics (Chaudhari et al. 2021). Disease severity and incidence considerably reduced as compared to the control (Chen et al. 2011) (Tables 6 and 7).

Table 6 Effect of Biochar in the management of bacterial diseases
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Table 7 Effect of Biochar in the management of fungal diseases
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According to Hu et al. (2023), using biochar increased the relative number of helpful bacteria, which helped to naturally decrease bacterial wilt (Erwinia tracheiphila) in cucumbers. Bacillus, Telmatobacter Chlorochromatium, Chthoniobacter, Bradyrhizobium Geobacillus, Leptospirillum, Microvirga, Aeromicrobium, Marisediminicola, Pseudoxanthomonas, Corynebacterium,and Burkholderia,were among the beneficial bacteria that the biochar treatments greatly enhanced in soil (Chen et al. 2020). Rice hull biochar proved useful in preventing the bacterial wilt disease. Through altering soil chemical characteristics and microbial abundances, biochar additions dramatically reduced tobacco bacterial wilt in the field trial (Chen et al. 2020).

Biochar applied at a rate of 2 to 3% (wt/wt), demonstrated their efficacy in decreasing bacterial wilt in tobacco and tomato plants. Improved soil physicochemical characteristics and an increase in bacteria and actinomycetes in the rhizosphere after biochar application lowers R. solanacearum swarming motility and root colonization capability (Poveda et al. 2021; Samal et al. 2024). Amendment of biochar decreased incidence of disease incidence up to 78%, and this positive effect of biochar could be associated with enhanced activity of soil antagonists and altered composition of amino acids as well as rhizosphere organic acids. Amendment of biochar increased citric acid and lysine and reduced salicylic acid help improve microbial activity that rendered rhizospheric conditions unsuitable for the development of R. solanacearum (Tian et al. 2021).

1.11 Biochar Effect on Phytopathogenic Fungi

By incorporating biochar into the soil, plant diseases by fungi may become less severe due to its managerial effects on the soil-plant-rhizosphere-pathogen system; both plant growth and disease progression may be impacted by the direct and indirect effects of biochar on the soil environment, host plant, pathogen, and rhizosphere microbiome. Numerous responses of biochar, including water adsorption capacity & holding capacity, redox activity, pH neutralization, and induced systemic plant resistance to fungal infections in some circumstances help managing with soil borne infections by pathogenic fungi (Graber et al. 2014). Soil enriched with biochar greatly reduced Fusarium wilt and chlamydospore production (Akhter et al. 2015). In tomato and pepper, biochar from citrus wood1-5% controlled B. cinerea and Leveillula taurica respectively. The utilization of biochar-treated pots resulted in a remarkable improvement in the growth of pepper plants compared to the unamended controls. This enhancement was evident in various plant parameters, including increased leaf area, canopy dry weight, number of nodes, as well as improved yields of buds, flowers, and fruits (Graber et al. 2010). “Numerous organic compounds from various chemical classes, such as n-alkanoic acids, hydroxy and acetoxy acids, benzoic acids, diols, triols, and phenols, have been detected in organic solvent extracts of the biochar. This has shown potential for enhancing plant performance through two distinct mechanisms. Firstly, the biochar appears to promote shifts in microbial populations towards beneficial plant growth-promoting rhizobacteria or fungi, possibly due to its chemical or physical properties. Secondly, when used in low concentrations, the biochar chemicals, many of which can be phytotoxic or biocidal at higher concentrations, exhibit stimulatory effects on plant growth, a phenomenon known as hormesis”. According to Meller Harel et al. 2012 pepper biochar controlled effectively Colletotrichum acutatum and Podosphaera aphanis. Necrotrophic fungus Rhizoctonia solani was also controlled by application of biochar (Verwaaijen et al. 2017). A reduced infection in a plant most likely is due to the development of systemic inducers of resistance (Elad et al. 2010) that work as a signaling cascade.

Fusarium oxysporum f. sp. asparagi and F. proliferatum are the causes of crown and root rot diseases that affect asparagus; allelopathic poisons released into the soil aggravate the disease. Application of hardwood biochar increases antagonists’ population helps promote systemic resistance against above mentioned Fusarium spp. (Elmer 2016). Biochar exerts beneficial effects of soil through altering soil properties, nutrients availability, as well as stimulating populations of antagonistic bacteria such as Pseudomonas and Arbuscular mycorrhizal fungi (AMFs) (Poveda et al. 2021).

Oomycetes fungi are the pathogens of numerous plant species including many food and cash crops (Hargreaves and van West 2019). Tree infecting species of oomycetes fungi i.e., Phytophthora spp., Pythium spp. have been treated with biochar. Zwart and Kim in 2012 experimented using 5% biochar W/V used against P. cinnamomi and P. cactorum and proved that biochar slows down disease and physiological pressure. Nevertheless, several studies have reported that the application of biochar increased the colonization of oomycetes group fungi P. ultimum in lettuce, sweet pepper, and basil, without any observable adverse impacts on the root system or plant growth (Gravel et al. 2013).

1.12 Biochar Effect on Phytopathogenic Nematodes

Plant-parasitic nematodes (PPN) are among the major obstacle responsible for biotic stress in plants as they are capable altering physiology and histology affect metabolic activities in vegetative as well as reproductive parts of plant resulting in considerable yield losses (Khan et al. 2022). Biochar application has shown to suppress population of plant pathogenic nematodes, hence been promoted as an eco-friendly management approach and an alternative to synthetic pesticides (Eche and Okafor 2020). In a greenhouse trial by Rahayu and Sari (2017) application of biochar resulted in increase of growth and biomass of coffee seedlings and suppressing the population of parasitic nematode in coffee seedlings. Using 0-4% concentration of biochar caused mortality of 37.5% (0.5%)-74.5% (4.0%) in coffee nematode, Pratylenchus coffeae.

Biochar derived from hard wood proved successful in lowering the population of P. coffeae, a migratory endoparasitic and significant damaging root lesion nematode of banana. Adding of biochar generated out of poultry litter dramatically decreased population of Meloidogyne javanica, Pratylenchus spp., Tylenchulus semipenetrans, Criconemoid spp. and Helicotylenchus spp. in grapevine (Rahman et al. 2014). Biochar incorporation reduced the abundance of the stubby-root nematode Trichodorus sp. in maize crops and the migratory endoparasites nematode P. penetrans in carrot crops. Five-year monitoring of the impact of biochar and manure added to low fertile yellow cinnamon soil showed significant decreasing of PPNs levels. The addition of biochar to rice potting soils reduced the crop’s susceptibility to the root-knot nematode M. graminicola (Stefanovska et al. 2022). Ikram and colleagues (2024) investigated effect of biochar alone and in combination with oil cakes of mustard, castor, linseed, coconut, and sesame against M. incognita. They reported increase in plant growth, fresh weight, total chlorophyll, dry weight, nitrate reductase activity, carotenoid levels, and decrease in nematode population, egg masses per root, and number of galls per root.

Biochar effects contribute to the prevention of root or foliar plant pathogens by modifying root exudates, soil characteristics, and nutrient availability, thereby impacting the growth of antagonistic microorganisms (Medeiros et al. 2021). The introduction of biochar in the roots trigger systemic plant defenses, leading to activated stress-hormone responses, changes in active oxygen species, and other internal plant alterations, which ultimately reduce foliar pathogenic fungus too (Poveda et al. 2021).

1.13 Comparison of Biochar with Chemicals Over Long Term Effects on Plants and Surrounding Ecosystems

Biochar and pesticides are two agricultural practices that have been extensively studied for their impact on plant growth, soil health, and overall ecosystem dynamics. Both methods aim to improve crop productivity and protect plants from pests and diseases, but they differ significantly in their mechanisms and long-term effects. This discussion explores the effects of biochar and pesticides on plants, soil, and ecosystems, with a focus on their long-term implications. Biochar has gained attention due to its potential benefits for plant productivity and soil health. When applied to soils, biochar improves soil fertility, water retention, and nutrient availability over the long term (Lehmann and Joseph 2015). The high surface area and porous structure of biochar enhance microbial activity and nutrient cycling, leading to increased plant growth and yield (Jeffery et al. 2011). Biochar does influence beneficial soil microbial communities that suppress plant pathogens in the rhizosphere (Inyang et al. 2016). As a result, biochar applications have shown a reduction in disease incidence and severity in various plant species (Azeem et al. 2023). Furthermore, the slow decomposition rate of biochar helps to sequester carbon in the soil for extended periods, contributing to climate change mitigation (Smith et al. 2008). In contrast, pesticides are chemical substances specifically designed to control pests and diseases in agricultural systems. Although pesticides can effectively suppress pests and protect crops, their usage raises concerns about environmental contamination, potential harm to non-target organisms, and the development of pesticide resistance (Bass and Basu 2011; Grube et al. 2011) (Fig. 7). The accumulation of pesticide residues in the soil can persist for years and may have detrimental effects on soil health and biodiversity (Kohler and Triebskorn 2013).

Fig. 7
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Long-term effects of biochar in comparison with chemicals. Biochar addition in the soil helps decrease in the leaching of pesticides and reduce residual load on plant system, contamination of soil & ground water and killing of beneficial micro-flora 

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2 Conclusion

After amendment of biochar in the soil, physico-chemistry of the soil is improved to support plant’s growth, sustainable production and food security. Various mechanisms of biochar make it an effective alternative tool for soil reclamation and rejuvenation. Use of biochar from different alternative organic sources have been proved as an alternative to improve soil fertility, nutrient absorption, water retention, microbial activity restores degraded land. Biochar acts as a carbon sink and contributes to long-term carbon sequestration to mitigate climate change impacts and emissions of greenhouse gases.

As a part of plant disease and pest management, biochar-based amendment is a promising method that is compatible with a circular economy focused on zero waste. Biochar manages plant diseases caused by soil-borne and other pathogens through a variety of deteriorating mechanisms such as antibacterial, fungitoxic, and nematotoxic effects, as well as the sorption of phytotoxic and allelopathic compounds that disease plants. Through various supporting mechanisms, such as inducing plant resistance, increasing the activities and abundance of beneficial microorganisms, and altering soil biotic and abiotic conditions biochar helps plant to grow and produce well.

As a result, introducing biochar into agricultural systems might provide a more ecologically sound and environmentally responsible means of enhancing crop productivity and long-term plant protection. Future studies should concentrate on investigating extremely productive strains, perfecting conditions, and evaluating a wide range of waste sources for biochar formation as well as their effectiveness in field tests.