VERMICOMPOST AND BIOCHAR EFFECTS ON THE MYCORRHIZAL SYMBIOSIS AND SOIL MICROBIAL COMMUNITY ASSOCIATED WITH GUAVA SEEDLINGS

Guava (Psidium guajava L.)  is a main horticultural crop throughout the tropical and subtropical zone (Das et al., 2017). Guava is widespread fruit in Egypt, as it is inexpensive and high in vitamin C, pectin, vitamin A, B2, and minerals such as phosphorus (P), calcium (Ca), and iron (Fe) (Ibrahim et al., 2010). Furthermore, guavas can grow in newly reclaimed soils due to their high adaptability and thrive in these soils (Ibrahim et al., 2010). Excessive nutrient availability in the soil during fertilization should be avoided because it generates an imbalance in the absorption of other elements (Souza et al., 2016; Montes et al., 2016). In the critical phase of fruit development, the relative nutritional imbalance of a specific nutrient impairs the yield and quality of guava fruits. Therefore, it is necessary to consider the dynamics of nutrient absorption in plants, which are supplied with high doses of fertilizers (Rozane and Couto, 2003).

     Guava has relatively high nutritional requirements, and it is typically grown in soils that are deemed low in fertility, necessitating fertilization with nearly all of the nutrients required for proper development (Rozane and Couto, 2003). As a result, nutrient export becomes a critical issue, with the order K > N > P > S > Mg = Ca varying depending on the cultivar (Cavalcante et al., 2008). For orchards established in the calcareous and alkaline subtropical soils, iron is the greatest limiting factor for the development of fruit trees (Zuo and Zhang 2011). In these soils, the high pH and high bicarbonate concentration decrease the solubility of Fe, thus reducing its absorption by the plants (Jeong and Connolly, 2009). Studies have indicated that the application of inorganic Fe in soil in order to meet the Fe demand of guava has not presented satisfactory results because Fe is quickly converted to a form (FeIII), which is unavailable to plants (Jeong and Connolly, 2009).

This word refers to the mixture of earthworm castings (faeces) and uneaten bedding and feedstock (organic material) collected from worm beds (Sherman, 2018). Vermicomposts, which are generated from organic wastes by interactions among earthworms and microorganisms in a mesophilic operation, are finely divided, fully stabilized organic materials with big microbial populations and activity (‏Ahmad et al., 2021). The enzymes that induce the biochemical degradation of organic waste are produced by microorganisms, and earthworms are the main drivers of the technique because they are involved in the indirect activation of microbial populations via fragmentation and ingestion of fresh organic matter, resulting in a larger surface area available for microbial colonisation and thus dramatically increasing microbiological activity (Edwards et al., 2010). Most nutrients are present in forms that are easily taken up by plants in vermicompost, which is a stable, finely divided peat-like substance with a low C:N ratio, high porosity, and high water-holding capacity (Domfnguez, 2004).

      Vermicomposting is the microbial composting of organic wastes via earthworms to produce organic fertilizer with greater organic matter, organic carbon, total and accessible N, P, K, and micronutrients, as well as microbial and enzyme activity (Singh et al., 2020). Vermicompost includes nutrients in forms that are easily absorbed by plants, such as NO₃, soluble P, exchangeable potassium, Ca, and Mg, according to Parthasarathi (2004). Humic compounds (humic acids, fulvic acids, and humin) are abundant in vermicompost,

providing multiple locations for chemical reactions as well as microbial components that support plant growth. and disease suppression through the activities of bacteria (Bacillus), yeasts (Sporerobolomyces and Cryptococcus), and fungi (Trichoderma); and chemical antagonists such as phenols and amino acids (Domfnguez, 2004). Vermicompost is largely composed of C, H, and O, but it also contains nutrients including NO₃, PO₄, Ca, K, Mg, S, and micronutrients that have similar effects on plant development and crop yield as inorganic fertilizers applied to soil (Singh et al., 2008).

        Vermicomposting is a biological and chemical process that uses earthworms and microorganisms to recycle nutrients. As a result, vermicompost is regarded as a nutrient-dense biofertilizer with a diversified microbial community (Pathma and Sakthivel, 2013). Vermicomposting is an aerobic bioxidation method in which waste organic matter is decomposed and given to earthworms, which produce vermicasts rich in nutrients and microorganisms (Cynthia and Rajeshkumar, 2012).

      Vermicomposting and composting are two distinct processes, and it's crucial not to confuse the two (Sherman, 2018). Composting is a controlled process that uses biologically generated heat to turn organic materials into a beneficial soil additive under aerobic conditions. A vermicomposting pile or worm bin, on the other hand, should be kept cool to avoid overheating (Cai et al., 2018). In a vermicompost pile, high temperatures can kill worms, and the types and amounts of microorganisms vary as the pile reaches thermophilic temperatures. The vermicomposting process produces a high diversity and number of microorganisms because the temperatures during vermicompost production, it is suitable for worms (Sherman, 2018).

    The high temperature through the compost makings phases causes some nutrients, such as ammonium, to be lost. On the other hand, vermicompost does not lose some nutrients, such as NH₄, because the temperature is kept low during the manufacturing process (Cai et al., 2018). Unlike compost, vermicompost is made in a mesophilic environment, where microbes biochemically decompose the organic waste, earthworms are the key players in the process, since they aerate, condition, and fracture the substrate, dramatically affecting microbial activity (Joshi et al., 2020). Earthworms act as mechanical blenders, fragmenting organic matter and altering its physical and chemical status by gradually lowering the C: N ratio and increasing the surface area exposed to microorganisms, making it more conducive to microorganism activity and further decomposition (Dominguez et al., 2010). Vermicompost has high nutrient availability and microbial diversity, so vermicompost outperforms ordinary compost and industrialized fertilizers in terms of crop growth and soil microbial community structure (Zhao et al., 2017).

2.2.1 Earthworms and raw  material  for vermicomposting

      Earthworms are soil-dwelling macroscopic clitellate oligochaete annelids. They are bilaterally symmetrical segmented worms with an outer gland (clitellum) for creating the egg case (cocoon), a sensory lobe in the front of the mouth (prostomium), and an anus at the end of the worm's body, each segment having a some of the bristles (setae) (Edwards et al., 2010). They are hermaphrodites, and reproduction is often accomplished via copulation and cross-fertilization, with each mated individual producing cocoons holding 1–20 fertilized ova. The tough cocoons, which are small and generally lemon-shaped, though the form varies by species, are usually deposited on the soil surface, unless in dry weather when they are deposited deeper layers. After an incubation period that differs depending on the earthworm species and ambient factors, cocoons hatch. When hatchling earthworms emerge from their cocoons, they are unpigmented and just a few millimeters long. Within a few days, they develop adult pigmentation. They reach sexual maturity within a few weeks of emergence, assuming good conditions. Distinguishes mature individuals of most vermicomposting species by the clitellum, a pale or dark-colored swelling band found behind the vaginal pores, The fibrous cocoon is secreted by the clitellum, and the clitellar gland cells create a nourishing albuminous fluid that fills the cocoon. Although they do not add segments, earthworms have indeterminate growth and can continue to expand in size after finishing their sexual development (Cao et al., 2021). According to Reynolds, (2004), the oligochaeta has around 8300 species, with nearly half of them being terrestrial earthworms. The most familiar earthworms in Europe, Western Asia, North America, and many other regions of the world belong to the Lumbricidae family, whereas many common earthworms in West Africa belong to the Eudrilidae family. The Microchaetidae are found in South Africa, the Megascolecidae in Australia and other regions of eastern Asia, and the Glossoscolecidae in Central and South America. However, only 8-10 species are discovered to be suitable for vermicomposting. Epigaeic species (litter dwellers who live in the organic horizon) like Eisenia fetida and Eudrilus eugeniae are the ideal earthworms for vermiculture and vermicomposting. Earthworms eat a variety of organic wastes and reduce their volume by 40–60%. Each earthworm weighs around 0.5 to 0.6 gm, eats waste comparable to its weight, and excretes solids equal to about half of the rubbish it consumes in a day (Parhi et al., 2019).

      These worms prefer to live on top soil and like to eat organic leftovers like vegetable waste, compost, and organic bedding, resulting in richer casting than those that live in plain soil. These worms have been identified as the only species of worm capable of eating up to half of its body weight on a daily basis. They are capable of decomposing and decaying natural remains and converting them into high-quality organic compost. Furthermore, the aforementioned earthworm species are resistant to temperature and moisture changes. Furthermore, these species proliferate quickly and remain active throughout the year, degrade organic material quickly (rapid casting), and aid in the faster preparation of vermicompost. Lumbricus rubellus, Perionyx sansibaricus, Perionyx excavatus, Eisenia andreii, and other species of red worms or red wigglers could also be utilised successfully in vermicompost production (Domínguez, 2018).

       Cattle manure or farmyard manure is used as a raw substance to eat by worms for vermicomposting, but any material that decomposes readily, such as weeds, vegetable and fruit wastes (leaves and rinds), agricultural residue, animal roughage, and municipal wastes of organic origin could also be used (Maronezi et al., 2022). The organic waste eaten by earthworms is physically broken down in the gizzard, where it is subsequently exposed to numerous enzymes produced into the lumen by the gut wall and related bacteria, including protease, cellulose, lipase, chitinase, and amylase. Complex macromolecules are broken down into simpler ones by the enzymes mentioned above. Vermicompost is structurally stable thanks to mucus secretions from the gut wall. Earthworms absorb just 5-10% of the ingested material for growth, with the remainder expelled as casting  (Ahmad et al., 2021).

• Factors influencing of earthworms populations:

    Different factors control on cultivation and maintenance of healthy earthworm populations which are the most important are food, pH, moisture, light, temperature, aeration, and predators.

2.2.2.1 Food

   Food and its abundance are two of the most critical factors that influence the establishment and survival of earthworm populations. Higher nitrogen levels promote faster growth and more cocoon production. The fresh green matter is difficult to digest (Domínguez, 2018). Before earthworms eat new garbage, they must first decompose through microbial activity. The C/N ratio is a key determinant of earthworm population size. It becomes more difficult to extract adequate nitrogen for tissue formation as the C/N ratio of the feed material rises. When the organic carbon level of the soil is low, earthworms have a hard time surviving (Gajalakshmi and Abbasi 2004).

 2.2.2.2 The moisture content of organic wastes

     The moisture content of organic wastes and the rate of growth of earthworms have a strong link. Moisture levels must be kept at 50% to ensure that microbial activity is high and that the food item is easy to digest. Also, anaerobic conditions resulting from too much water lead to incompletion of the process of vermicomposting (Dominguez, 2018).

 2.2.2.3 Temperature

    Metabolism, reproduction, and growth for earthworms are all affected by temperature. Sun-exposed soils quickly lose moisture and are frequently free of earthworms (AL-malik et al., 2020). Earthworms maintain lower body temperature than the soil and organic matter through metabolic modifications (Curry 2004).

    The responses of earthworms to temperature changes are fairly complex. Kiyasudeen et al. (2016) investigated the ability of different earthworm species to grow in sewage sludge, concluding that all of these species have a preferred temperature range of 15°C to 25°C.

2.2.2.4 Light

     Earthworms are extremely light-sensitive. Earthworms migrate away from bright light because their photoreceptor cells detect it. For this reason, deep digging anecics and other species only come to the surface at night (Gajalakshmi and Abbasi 2004).

2.2.2.5 pH

      Changes in pH are difficult for earthworms to tolerate. Earthworms prefer a neutral pH. When the medium is acidic, earthworms find it hard to survive and move or die (Dominguez, 2018).

2.2.2.6 Aeration

       Earthworms don't have specialized respiratory organs, thus oxygen and carbon dioxide pass through their skin. As a result, anaerobic conditions are extremely dangerous to earthworms. E. foetid has been documented to migrate in large numbers from a water-saturated substrate low in oxygen or accumulating carbon dioxide or hydrogen sulfide (Edwards et al., 2010).

2.2.2.7 Ammonia and Salts

       Earthworms are extremely sensitive to NH₃ and are unable to thrive in organic wastes with high quantities of this cation. They also perish in wastes containing substantial amounts of inorganic salts. Both NH₃ and inorganic salts have very sharp cutoff points between nontoxic and toxic (<1 mg·g-1) of ammonia and <0.5% salts (Zeguerrou et al., 2021). On the other hand, organic wastes containing significant levels of ammonia can be made acceptable once the ammonia is removed before using or water leaching (Edwards et al., 2010).

2.2.2.8 Predators

      Many kinds of ants, birds, toads, salamanders, snakes, moles, cats, rats, dogs and other animals' prey on earthworms. When moles catch earthworms, they bite off three to five anterior segments to inhibit motility and keep them in their burrows. Earthworms are also eaten by a variety of invertebrates. Flatworms, centipedes, and staphylinid beetles are examples (Curry 2004).

2.2.3 Steps involved in vermicompost production

      The creation of high-quality vermicompost from raw waste necessitates a thorough understanding of the process. The following are the many steps involved in vermicompost production:

       Choose a location for vermicomposting and smooth the surface. Then, using bricks, construct a box of roughly 10 x 3 x 3 feet (L x B x H). On the other hand, the size of the bed could be reduced or increased depending on the amount of material available and the requirement. Spritz water on the box's surface to moisten it (Rostami et al., 2009).

     Spread a 2-3-inch-thick layer of paddy straw or dried leaves at the bottom of the box. Once again sprinkle a small amount of water over the dried layer. Spread a 1-1.5-foot-thick layer of cow dung or farmyard manure uniformly over straw or the leaves layer and water it to keep it moist. It's best if the cow dung isn't too fresh. Because fresh cow dung produces a lot of heat and can kill earthworms, it should be at least 10-15 days old. Also, cow dung should not be very old because it has decomposed and provides little food for earthworms (Kumar et al., 2018). 

        Then, add kitchen trash such as fruit rinds, vegetable leaves and or grasses, and animal roughages by slicing them into little bits. Spread a homogeneous layer of cow dung around 1-1.5 feet thick and a suitable amount of water. Over the layer of cow manure, spread around one kilogram of vermiculture (each containing about 800–1000 earthworms). Spread a 2-3-inch layer of green leaves over the top of cow manure or farmyard manure and water it again. lid the vermicompost box with gunny sacks or jute (Rostami, 2011). Sprinkle water over the gunny bags on a daily basis to keep the vermicompost box at the ideal moisture and temperature.

      The box should have a moisture content of 35-40% and a temperature of 15-30°C. Sprinkle water on a frequent basis to maintain ideal circumstances for earthworm growth and function. Provide a roof over the vermicompost unit if it is set up in an open place, so that shady conditions can be maintained for the unit and earthworms can be protected from direct sunlight and rain (Kumar et al., 2018(. Vermicompost is available in around 8–10 weeks. When fully mature, the vermicompost color is dark brown, highly porous, granular, and odorless (Ahmad et al., 2021).

2.2.4       Harvesting and storage of vermicompost

When the vermicompost is finished, cease watering around a week ago and construct a compost heap. The color of the layer will be black. It's a sign that the raw materials and castings are being turned into compost (Rajendran et al., 2008). The earthworms will now begin to move downward, eventually gathering at the bottom of the heap. Remove the vermicompost from the top of the heap and place it in the shade for additional processing, such as sifting and packing. It should have a minimum moisture content of 40%, and sunlight should not shine directly over heaped vermicompost, since this could induce moisture and nutrient loss. Now filter the vermicompost and, if any earthworms remain, move them to the next fresh bed. Because the lower half of the vermicompost heap has a large number of earthworms, it might be employed as vermiculture to prepare vermicompost once again. Vermicompost is now ready for use to fertilize plants. If the optimum moisture content of 40% in the vermicompost is maintained, it can be stored for at least one year without losing its quality (Kumari et al., 2021).

2.2.5 Why used vermicompost?

        Composts have a lower nutritional value than vermicompost. This is due to the higher rate of mineralization and humification grade caused by earthworm activity (Joshi et al., 2015). It also has a lot of porosity, drainage, aeration, and water storage capacity (Manivannan et al., 2009). Vermicompost boosts the activity of microorganisms like bacteria, fungus, and actinomycetes, making it ideal for plant growth (Ferreras et al., 2006). Vermicompost contains plant-available nutrients like nitrates, exchangeable potassium, soluble phosphorus, magnesium, and calcium (Padamanabhan, 2021). Plant hormones and other microorganism-produced plant growth influencing elements are also present in vermicompost (Joshi et al., 2015). Inorganic wastes handled by earthworms were found to produce auxins and cytokinin (Vuković et al., 2021).

2.2.6 Benefits of Vermicompost

    2.2.6.1 In soil proprieties

      Vermicompost improves the chemical, physical, and biological conditions of soils, allowing plants to thrive and absorb nutrients (Indira, 2016).

    Vermicompost led to increase porosity of the soil and aggregation of the soil particles by the work of microorganisms in the vermicompost which are known to produce polysaccharides that increased a cementing action between the soil particles (Manivannan et al., 2009). According to Zaller (2007), polysaccharides help to sustain soil aggregates, and fungal mycelia may also help with soil aggregation. Also, Manivannan et al., (2009) discovered that vermicompost application reduces the bulk density of the soil, resulting in increased aeration and evacuation. Vermicompost enhances the structure of soil because organic matter is present in vermicompost (Sekar and Karmegam, 2010).

       Vermicomposting led to a low C: N ratio in soil, in addition to boosting the availability of several nutrients for plants (Theunissen et al., 2010). When the soils were fertilized with vermicompost, the available NPK in the soils increased (Chaoui et al., 2003). Low EC was detected in soils treated by vermicompost, according to Manivannan et al., (2009). Also, Zhao et al., (2019) found that application of vermicompost led to a decrease of pH in the soil after the addition of vermicompost, on the other hand, it was increased in the concentrations of soil water-soluble organic carbon, available nitrogen, available phosphorus, and organic matter. Also, according to Srikanth et al., (2000), vermicompost has been proven to improve soil organic carbon content. In addition, Zhao et al. (2019) suggested that vermicompost could increase soil fertility and yield, and also alleviate the continuous cropping challenge in a greenhouse. The majority of studies have found that vermicompost has a strong positive impact on soil fertility (Wang et al, 2018b). Also, Theunissen et al., (2010), reported an increase in concentrations of amino acids and phenolics in vermicompost-fertilized soil. With respect to the soil mineral nutrients, vermicompost increased the concentrations of the exchangeable elements, N, Zn, Ca, Mn, Mg, Cu and P. The release of chelating agents from organic matter decomposition may have prevented micronutrient precipitation, leaching, and oxidation, resulting in a high in available nutrient status in the soil (Indira, 2016).

   2.2.6.2 Microbial community

        Liu et al., (2017) discovered that vermicompost can raise the soil number of fungal and bacterial. Different researchers have discovered a variety of bacteria of various kinds in vermicomposts produced by various earthworm species, such as Pseudomonas oxalaticus (Pathma and Sakthivel 2012) in Pherentimasp, Pseudomonas putida and Rhizobium japonicum in Lumbricus rubellus, Azospirillum, Azobacter, Nitrosomonas, Nitrobacters, Ammonifying bacteria and phosphate solubilizers (Gopal et al., 2009; Pathma and Sakthivel, 2012) in Eudrilussp. Vermicompost boosts microorganism activity as well as microbial biomass (Ferreras et al., 2006). encourages the creation of a unique microbial population in the rhizosphere, distinct from that found in plants fed with mineral fertilizers or alternative organic fertilizers such as manure (Aira et al., 2010). Vermicompost considerably boosted the functional diversity of the soil microbial population. This could be owing to vermicompost's high nutritional availability and microbial diversity (Pathma and Sakthivel, 2012).

     2.2.6.3 Plant growth

    Vermicompost has great effects on the growth of plants such as the relative growth rate of cucumber (Cucumis sativus) seedlings when using vermicompost were found to be substantially greater than in compost (Sallaku et al., 2009). Dheware et al. (2020) discovered that using vermicompost resulted in greater flowering in guava (Psidium guajava L). In addition, Sourabh et al., (2018) discovered that when vermicompost was applied to guava, the maximum plant height, fruit set, flowers per branch, average fruit weight, the number of fruits, and yield increased (Psidium guajava L).  

    Pawar et al., (2020) reported that the use of vermicompost improved the growing plant, fruit quality and yield, of sweet orange. Also, vermicompost enhanced the peach fruit's quality (Hashemimajd and Jamaati-e-Somarin 2011). In addition, tomato seedlings (Lycopersicum esculentum) with vermicompost had a higher germination rate (%) than tomato seedlings without vermicompost (Atiyeh et al., 2000). The presence of important nutrients and diverse necessary elements like P and K in vermicompost stimulates the development of plants (Fernandez-Luqueno et al., 2010).

      The plant height of eggplant (Solanum melongena L.)treated with vermicompost has increased as compared to plant height without vermicompost (Vijaya and Seethalakshmi, 2011). In comparison to plants without vermicompost and plants treated with vermicompost, the plant height of Crossandra (Crossandra undulaefolia) increased in pots treated with vermicompost (Gajalakshmi and Abbasi, 2002).

     Mirakalaei et al., (2013) found that vermicompost application increased the root length and root fresh weight of Lilium longiflorum.The use of vermicompost improved root dry weight, root fresh weight, and root length of pea (Pisum sativum) (Khan and Ishaq, 2011). Likewise, Gutierrez-Miceli et al., (2008a) found that vermicompost boosted sorghum (Sorghum bicolor (L.) Moench)  root dry weight. The use of vermicompost boosted the root length of crossandra, according to Gajalakshmi and Abbasi (2002). Application of vermicompost with Phosphorous improved root length of setaria grass as compared to control and other treatments (Sabrina et al., 2013). Plants treated with vermicompost showed raised root growth, suggesting higher macro-and micronutrient uptake (Theunissen et al., 2010). Vermicompost's hormone leads to an increase in root biomass, root growth, and improved plant growth (Lenin et al., 2010).

     According to Singh et al. (2011), vermicompost application increased the shoot high, shoot fresh wight and shoot dry wight of French bean  (Phaseolus vulgaris). The application of vermicompost improved the length of shoots of Andrographis paniculata, according to Vijaya et al., (2008). Uma and Malathi (2009) discovered that applying vermicompost to Amaranthus species improved the shoot fresh weight of plants. Shoot lengths of groundnut (Arachis hypogaea) Mycin et al  (2010), and garlic (Allium stivum) Suthar, (2009) improved with using vermicompost. The shoot height, shoot dry and fresh weights and stem diameter of Lilium plant (Moghadam et al., 2012) and stem diameter of okra (Abelmoschus esculentus) (Ansari and Sukhraj, 2010) improved with applying vermicompost. Atiyeh et al., (2000) reported that application of vermicompost led to the increasing weight of shoot dry of tomato (Lycopersicum esculentum).

     Madan and Rathore (2015) reported that when applying vermicompost led to an increase in the growth of plants (Cicer arietinum) which led to increased root length, shoot fresh weight, root dry weight, and total chlorophyll. The use of vermicompost for pepper plants led to increase shoot fresh weight and root dry weight (Alaboz et al., 2017). The amount of chlorophyll in the leaves rose when vermicompost was applied  (Mirakalaei et al., 2013).

   Because vermicompost is rich in substances needed for plant growth, such as plant hormones and humic acid, Ravindran and Mnkeni (2016) discovered that vermicompost might be used as a soil amendment to improve plant growth, yield, and quality of yield. The uptake of the plant macronutrients like N, P, K, and Mg located in vermicompost, affects the chlorophyll biosynthesis and therefore increases photosynthesis (Al Jaouni et al., 2019). The inclusion of humic acids (Arancon et al., 2005) as well as micro and macronutrients in vermicompost promotes plant growth (Atiyeh et al., 2002; Fernandez-Luqueno et al., 2010). With the usage of vermicompost, (Manivannan et al., 2009) found an increase in the rates of nutrient uptake as well as an increase in the symbiotic microbial association in plants. Vermicompost also includes more humic acid and biologically active compounds like plant growth regulators, according to Fernando and Arunakumara (2021).

    2.2.6.4 Nutrients content

      Application of vermicompost improved uptake of nutrients in guava (Trivedi et al., 2012). Vermicompost increased the level of organic carbon in the soil, the availability of nutrients, and the concentrations of nutrients in the leaves of mango trees (Adak et al., 2014). The N, P, K, and Mg concentrations of plants of Amaranthus species increased after vermicomposts were applied, according to Uma and Malathi (2009). In addition, Mycin et al. (2010) found that using vermicompost increased the N, P, K, and Ca concentrations of groundnuts (Arachis hypogaea). In addition, chand et al. (2011) discovered that vermicompost application boosted N, P, K, Fe, Zn, Cu, and Mn concentrations in geranium plants (Pelargonium species). As well as application of vermicompost increased uptake of K, P in african marigold (Tagetes) (Paul and Bhattacharya, 2012). The use of vermicompost enhanced the level of K, Ca, Zn, and Fe in the Lilium plant, according to Moghadam et al., (2012).  Sabrina et al., (2013) reported that K, Mg, Ca uptake of plants rose on using vermicomposts. The use of vermicomposts improved the amount of vitamins, primary metabolites, and mineral content in date palm fruits this is due to the role of vermicomposts in enhancing soil fertility and health  (Al Jaouni et al., 2019).

       In addition, Bhattacharya et al., (2012) found that adding vermicompost to soils boosted nutrient availability. Joshi et al., (2015) also found that adding vermicompost to the soil enhanced the availability of N, Ca, P, K, and Mg. Vermicompost presents microorganisms into the rhizosphere of plants, resulting in increased N and P availability through biological P solubilization and biological nitrogen fixation   (Mycin et al., 2010). Also, vermicompost enhances soil properties, resulting in increased nutrient uptake (Mycin et al., 2010). Humic acids located in vermicompost boost nutrient availability and nutrient uptake by plants (Reyes-Perez et al., 2021). As well as vermicompost includes nutrients in forms that are easily absorbed by plants according to Parthasarathi (2004). Vermicompost has more available nitrogen than conventionally compost (Taleshi et al., 2011).

2.2.7 Application of vermicompost in soil

     The amount of vermicompost applied depends on its quality, nutritional content, and the crop to which it will be put. In vegetables apply 10–12 t/ha vermicompost, 5–6 t/ha for field crops, and 8–10 kg per fruit tree depending on age, but in flower pots, use 100–150 g of vermicompost per pot (Kumar et al., 2018). However, numerous research have found that varied rates of vermicompost produce the best results in their different experiments. Nagavallemma et al., (2004) found that vermicompost application of 5 t/ha resulted in the best tomato yield. In another experiment, vermicompost application of 2.5 t/ha resulted in the maximum rice yield  (Angadi and Radder, 1996). In addition, the use of 10 t/ha vermicompost yielded the best yield in Cabbage (Indira, 2016). Azarmi et al., (2009) found that applying vermicompost at a rate of 30 t/ha resulted in the highest cucumber stem dry weights (Cucumis sativus). Also, using vermicompost at a rate of 20 t/ha enhanced the plant height of Matricaria chamomilla (Hadi et al., 2011). In addition, Naik and Babu (2005) found that guava plants treated with 10 kg vermicompost had the most shoots per tree, the highest shoot, and the most leaves per shoot. The fact that plants respond differently to varied doses of vermicompost could be related to the release of varying amounts of accessible nutrients and growth promoters (Kashem et al., 2015).

2.3 Biochar

2.3.1 What is biochar?

       The word "biochar" was used to describe charcoal made in a controlled setting with the goal of being added to the soil (Lehmann et al., 2006). When compared to unheated biomass, biochar chemical and physical features similar to charcoal, such as a high C content, large surface area, low nutritional content, and cation exchange capacity (Blanco-Canqui 2017). Biochar is made by pyrolyzing biomass at temperatures ranging from 350 to 600°C in an oxygen-depleted environment (Sohi et al., 2010). Several authors have defined biochar in similar ways. It is a 'black carbon produced through biomass pyrolysis' (Lehmann et al., 2006); 'the carbon high materials manufactured from the pyrolysis slow  (heating with limited of oxygen) of biomass' (Chan et al., 2007); and a porous substance and fine-grained, like in appearance to charcoal created by natural combustion burning or biomass burning under limited of oxygen conditions' (Sohi et al., 2009). Biochar is a solid byproduct of thermochemical conversion (pyrolysis) of biomass that can be put into soils to absorb carbon to prevent climate change (Wang and Wang 2019), improve soil fertility (Spokas et al., 2012), and improve crop productivity (Atkinson et al., 2010; Jeffery et al., 2011). Biochar has a high porosity, organic C, and adsorption capacity, (Shim et al., 2015; Rajapaksha et al., 2015) and high cation exchange capacity (CEC) (Joseph et al., 2010; Spokas et al., 2010). Adding biochar to the soil leads to a change in the properties of the soil (Mukherjee et al., 2014).

    Solid (biochar), gas (syngas), and liquid (bio-oil) bioenergy co-products are currently created by pyrolysis. During pyrolysis, polymerization and cleaving reactions occur, resulting in the formation of thermally stable fixed carbon (aromatic) structures that are resistant to microbial decomposition (Harvey et al., 2012).

      As a carbon-rich material with various acidic and basic functional groups, biochar showed promising results (i.e., 2–200 mg g^-1adsorption capacity) in organic and inorganic contamination removal from water (e.g., phenol, methylene blue, (Cu²⁺ , Cd⁺³ , Pb⁺²  and  Zn⁺²)  (Mohan et al., 2014).

2.3.2 Biochar production

         Pyrolysis, gasification, and carbonization are thermochemical processes for converting biomass into biofuels, biochar, and other bio-based products (Singh and Gu, 2010). Biochar is a solid result of pyrolysis, which is the conversion thermochemical of feedstock at temperatures exceeding 300^oC in the absence of oxygen. Biochar is made up of carbon (C), hydrogen (H), oxygen (O), sulfur (S), and ash, so, it is not pure carbon. Its structure reflects the feedstock's shape (Boateng et al., 2015).

       In combustion, pyrolysis is always the initial phase. At various temperatures, pyrolysis causes the polymeric building components of biomass, hemicellulose, cellulose, and lignin, to undergo diverse reactions such as cross-linking, depolymerization, and fragmentation (Wang et al., 2020). Non-condensable and condensable (tars) volatiles, as well as char, are the principal results of biomass pyrolysis. The condensable volatiles are usually classified as liquids (bio-oil), Non-condensable volatiles include carbon dioxide (CO₂), carbon monoxide (CO), and hydrogen (H₂) (Boateng et al., 2015).  

        The type, composition, and nature of the feedstock, particularly the lignin and ash contents, as well as process variables such as pressure, temperature, vapour residence time, particle volume, heating rates, and heat integration, affect pyrolysis product yields (Chi et al., 2021). Similarly, the density, ash content, particle size distribution, moisture content, and pH of biochar are all affected by the kind, nature, and origin of the feedstock, as well as the pyrolysis reaction circumstances (Yaashikaa et al., 2020). Wood-based biochar, for example, is said to be gritty and resistant, with a carbon concentration of up to 80% (Demirbas, 2004). Due to the resilience of lignin to heat breakdown, biomass with high lignin concentration (e.g. olive husks) provides significant biochar outputs (Verheijen et al 2010).

    Based on conditions of pyrolysis, it can be classified into three essential groups, slow pyrolysis, intermediate, and pyrolysis fast (Boateng et al., 2015). The process' energy can be supplied in one of four ways: (i) directly as the heat of reaction, (ii) directly by flue gases from the combustion of by-products and/or feedstock, (iii) indirectly by flue gases via the reactor wall (iv) indirectly by heat carrier other than flue gases.      

    Conditions of pyrolysis that prefer increased biochar yields are: (i) high ash, lignin, and nitrogen contents in the biomass, (ii) low pyrolysis temperature (<400^oC), (iii) high operation pressure, (iv) extended vapor residence time, (v) extended vapor/solid contact, (vi) low heating rate, (vii) big biomass particle size, and (viii) optimized heat integration (Yu et al., 2017).

2.3.3 Sources of biochar

     Biochar could be created from a different of organic sources and under a variety of conditions, resulting in a variety of products with varied qualities (Mitchell et al., 2020). It can be made from a different of biomass sources, including barks and woods, agricultural wastes like olive husks, corncobs, and fallen leaves from fruit trees (Tripathi et al., 2016), green waste (Chan et al., 2007), animal manures, and other waste products (Lima et al., 2008). Biochar is a combination of char and ash, with the majority of the carbon (C) content (70–95%) (Luostarinen et al., 2010). It can also be created from Poultry litter (Revell et al., 2012), sewage sludge (Khan et al., 2013), rice husk (Carter et al., 2013; Lu et al., 2014), wheat straw (Junna et al., 2014), and a variety of other materials can be used to make it.

2.3.4 Properties of biochar

  2.3.4.1. Physical properties

      The nature of the biomass and the pyrolysis conditions have direct effect on the physical qualities of biochar. During various pyrolysis processes, attrition, fracture development, and microstructural rearrangement occur, modifying the biomass's original structures to varying degrees (Major et al., 2009). The mass of the feedstock is lowered as the pyrolysis process progresses (volatile organics are produced), resulting in a disproportional amount of volume loss or biomass shrinkage. mineral skeletons and C approximating the essential structure and porosity of the raw materials is created at the finish of the pyrolysis step. The presence of plant cellular structures within the coal and wood-derived biochar, which contribute to the majority of the biochar macro porosity, has been proven (Downie et al., 2009).

       The macropores can be transformed into micropores and meso (Zabaniotou et al., 2008). Overall, the physical structure of biochar produced by pyrolysis is shaped by biomass pretreatment, heating rate, reaction temperature, reactor type and dimension, residence period, carrier/purge gas flow rate, pressure, and biochar post-modification procedures. Pyrolysis fast of feedstock, for example, produces biochar with a small surface area. By raising temperatures of reaction to the point where any further temperature increase causes deformation, a perfect physical structure of biochar could be produced. Biochar produced at temperatures above 400°C, (Downie et al., 2009), contained substantial aromatic hydrocarbon concentration and was extremely disorganised in amorphous material. Conjugated aromatic C sheets that are organized turbostratically develop as the reaction temperature drops. Finally, at temperatures of 2500⁰C, the biochar resembles a graphitic structure with the order in the third dimension. More specifically, as reaction temperature drops, the production of structured regular spacing between planes declines, interplanar distances increase, and molecular organization decreases (Downie et al., 2009).

      2.3.4.1.1 Nano- and macro-porosity

        Distribution pore-size is one of the most essential physical features of any generated biochar, as it determines its industrial application potential. The entire pore volume of biochar is made up of micropores, mesopores, and macropores (pores with internal diameters of > 50 nm, 2-50 nm, and less than 2 nm, respectively) (Rouquerol et al., 2013). Micropores are the most important contributor to biochar surface area, as they adsorb efficiently minute molecules (such as solvents and gases). On the other said, mesopores, play an essential role in many adsorption liquid-solid processes (Downie et al., 2009).

Micropore volume might be enhanced by extending biomass pyrolysis at more elevated reaction temperatures, which would provide the necessary activation energies and reaction time, i.e., more organization structural in biochar molecules (Downie et al., 2009). Furthermore, at greater pyrolysis temperatures, the volatile content of the feedstock is liberated, resulting in larger pores (Shaaban et al., 2014). Slow pyrolysis improves the porosity of woody biochar by decomposing the lignin component more slowly (Weber and Quicker, 2018). When the pyrolysis temperature exceeds a certain threshold (for example, 400^oC), the biochar's specific surface area rapidly expands, which led to the thermal condensation of biomass and the production of micropores (Li et al., 2019a). Feedstocks containing aromatic lignin cores, and also, ester groups and aliphatic alkyl, produce biochar with greater surface areas when pyrolyzed at extremely high temperatures (Tomczyk et al., 2020). At temperatures above 800-1000^oC (particularly for slow heating rates), the expansion in specific surface area becomes minimal, and at temperatures beyond 850^oC, the solid matrix shrinks, resulting in decreased porosity. It should be mentioned that in some cases, the wall between two nearby micropores might be damaged by high temperatures (Zhang et al., 2004). The pore enlargement diminishes the micropore volume while increasing the total pore volume of the biochar. The heating rate is another component that determines the micropore volume. High heating rates cause the biomass to melt, forming macropores, whereas low heating rates increase the volume of micropores in the biochar generated (Cetin et al., 2004).

        Macropores serve as feeder pores, transporting absorbed materials into micropores and miso (Downie et al., 2009). The volume of macropores is critical for evaluating biochar's potential for sustainable agriculture (for example, hydrology, root movement, aeration, and as a place for soil microorganisms) (Palansooriya et al., 2019). Macropores have a smaller surface area than micropores but a larger pore volume.

   2.3.4.1.2 Particle-size distribution      

The particle size of biochar was determined by the stiffness of the feedstock Anti-shrink and attrition during the pyrolysis operation. The sizes of particles of biochar formed are generally lower than those of the feedstock.  Furthermore, during the pyrolysis operation, agglomeration can occur, resulting in biochar with greater particle sizes than the initial feedstock (Cetin et al., 2004). Biochar that is more vulnerable than the original feedstock may crumble due to post-mechanical loads (e.g., during handling). Slow pyrolysis with a heating rate of 5-30 ⁰C/min produced biochar particles with smaller size dispersion. The sizes of particles is inversely proportional to the temperature of the process. For example, increasing the reaction temperature from 450°C to 700°C has been shown to enhance the probability for smaller particles to develop in biochar (Downie et al., 2009). This could be owing to the lower tensile strength of biomass/biochar, which makes it more vulnerable to attrition.

      When greater heating rates are used, smaller feedstock particles are necessary to improve mass- and heat-transfer during pyrolysis process. As a result, the biochar produced will be exceedingly fine. Slow pyrolysis, on the other hand, produces larger charcoal particles due to lower heating rates and a longer residence time. Higher pyrolysis pressure, in addition to reaction temperature and residence time, may result in the creation of biochar with bigger particle sizes. Melting and subsequent particle fusion are more prominent in pressured pyrolysis, resulting in swelling and the creation of particle clusters (Cetin et al., 2004).

         2.3.4.1.3. Density

     When determining biochar physical parameters, apparent or bulk density, as well as solid density, could be taken into account. A rise in bulk density is usually accompanied by a reduction in solid density. As a result of the release of volatile and condensable chemicals and the creation of graphitic crystallites, biochar's real density is more elevated than that of the raw materials (Downie et al., 2009). The solid density of biochar rises as the temperature of pyrolysis rises (independent of the heating rate), leading the solid matrix to shrink and the level of carbonization to rise (Brown et al., 2006). On the other hand, the bulk density of biochar has lower (usually 0.3-0.43 g/cm3) than the wood predecessor due to biomass drying and carbonization. However, for gas adsorption and decolorization applications, the bulk density of biochar (activated carbon) might be as high as 0.50 g/cm³ and 0.75 g/cm³, respectively (Downie et al., 2009).

      Most biochar has solid densities of 1.47 - 1.7 g/cm³ due to residual porosity and structure (Brown et al., 2006). By raising reaction temperature (independent of heating rate) and duration, the formation of high-density turbostratic carbon fiber (from transformation of low-density disorganized ones) is aided (Kercher and Nagle, 2002). When compared to macro- and mesopores, the presence of micropores in biochar enhances its density (Downie et al., 2009). It's worth noting that pyrolysis temperature and biochar bulk density don't have a strong relationship. Generally speaking, the higher the bulk density of the feedstock used, the higher the it of the biochar generated (Byrne and Nagle, 1997).

         2.3.4.1.4 Mechanical strength

The mechanical strength of biochar is determined by its solid density, aromaticity, and crystallinity. To put it another way, the mechanical strength directly links with density, and therefore, with the porosity inversely. Only a few researches have looked at the mechanical strength of pyrolyzed biochar (Das et al., 2015; Zickler et al., 2006). Byrne and Nagle, (1997) reported that monolithic carbonized biochar wood exhibits reduced solidity (37%) and more increased strength (28%) as compared to virgin wood. According to these investigations, the stiffness of woody biochar and lowered modulus increase with increasing temperature, eventually reaching a plateau between 700 and 2000^oC. Any further increases in pyrolysis temperature would have a negative impact on the biochar's characteristics.

        According to Panahi et al., (2020), biochar generated from acacia and eucalyptus showed an initial decrease in impact strengths and compressive in response to high temperature (up to 600^oC), follow by an improvement. On the other side, biochar made from eucalyptus showed higher mechanical strength than biochar made from acacia. They also said that a gradual pyrolysis procedure (heating rate of 4^oC/min) would improve compressive strength over a quick process (30^oC/min). This is because of the reality that quick heating causes fissures in the solid structure of biochar due to the rapid release of volatile materials and evaporation of water. This explains why, compared to their high moisture equivalents, pyrolysis of biomass with lower moisture content produces biochar with higher mechanical strengths (Weber and Quicker, 2018).

      The mechanical strength of biochar can also be determined by the orientation and nanocomposite properties of feedstock (high density and high lignin content), as these qualities are practically unaffected during the pyrolysis process (Weber and Quicker, 2018). As a result, the produced biochar would preserve some of the microfibril angles of the cellulose and lignocellulose-derived honey-comb structure in the parent feedstock. Biochar is projected to have higher mechanical strength than parent biomass, but compressive strength and lower anisotropy due to increased order molecular (Downie et al., 2009).

     Mechanical strength is vital in determining biochar quality since it must be able to withstand wear and tear during environmental applications. Fruit stones/pits (e.g., date, olive, apricot) and nutshells (e.g., walnut, macadamia, hazelnut, and almond) are more appreciated for biochar synthesis with outstanding mechanical qualities on this premise (Aygün et al., 2003). Structure-mechanics properties of many waste-derived biochar were examined at different pyrolysis settings in a more recent work (Das et al., 2015). As a result, at higher pyrolysis temperatures (500^oC) and more extended residence times, the stiffness and modulus values increased (60 min). Surprisingly, the temperature of pyrolysis was found to be a stronger driver of biochar mechanical characteristics than residence time.

2.3.4.2 Chemical properties

Any pyrolysis technique could chemically transform biomass into biochar with a wide range of characteristics. Biochar's qualities are mostly determined by the biomass and pyrolysis temperature. In fact, using a data synthesis technique, biochar properties, and functions can be anticipated (Li et al., 2019a). Biochar yield typically declines exponentially as pyrolysis temperature rises, but the alkalinity (pH) of biochar rises linearly (rate, 0.5 - 1.4/100^oC) (Li et al., 2019a). The thermal breakdown of hydroxyl linkages and other weak links within the biochar structure at high temperatures is responsible for the pH increase. Due to the elimination of acidic functional groups, the cation exchange capacity of biochar has an inverse relationship with pyrolysis temperature (Panahi et al., 2020). Because biosolids are rich in minerals (such as P, Ca, Mg, Na, and K), which stimulate the production of O-containing functional groups on the surface of biochar during pyrolysis, biochar produced by biosolids have the highest cation exchange capacity (Agrafioti et al., 2013). In contrast to ash content, the volatile matter content of biochar decreases linearly as the pyrolysis temperature rises. The creation of ash is caused by inorganic minerals that remain after the decomposition of H, O, and C in biomass (Li et al., 2019a). The degradation of hydroxyl, azalide and other weakly-bonded groups in reaction to temperature increases is blamed for the decreases in these elements. However, C content (with the exception of certain volatile C) declines slowly, resulting in larger C proportions in the biochar produced at higher pyrolysis temperatures (Li et al., 2019a).

      Volatilization, entrainment in biochar, or retention as separate mineral phases could be the fate of biomass inorganic content (Wornat et al., 1995). The amount and distribution of minerals entrained in biochar is determined by the biomass and pyrolysis process parameters. Woody biomass (forest residues, scrap wood, and sawmill residues) often contain 1wt% ash. Grain, straw, and grass husks, which are high in silica content, could give high ash concentrations (up to 24wt%) (Raveendran et al., 1995). As previously stated, the loss of H, O, and C in biomass during pyrolysis concentrates the mineral concentration in biochar; for example, chicken litter- and bone-derived biochar can contain up to 45wt% (Koutcheiko et al., 2007) and 84wt% (Purevsuren et al., 2004) mineral contents, respectively. It has been hypothesised that biochar yield is independent of biomass mineral-ash content unless a solid catalyst is added, implying that in the presence of a solid catalyst, a larger biochar yield could be predicted from biomass with a higher mineral-ash concentration (Laird et al., 2009).

Mineral ash in biochar could also be influenced by pyrolysis process variables, such as reaction temperature and CO₂, steam, and O₂ partial pressure (Bridgwater and Boocock, 2006). During the thermal degradation of biomass, highly mobile ions such as Cl and K begin to vaporize at relatively low temperatures (Yu et al., 2005). Likewise, at low temperatures, N coupled with other organic compounds vaporizes (Schnitzer et al., 2007). On the other said, In the biomass cells S and P, are coupled with complex organic molecules and demonstrate well stability at low temperatures.

Some feedstock cell wall entrapped ions, like Ca (also linked with organic acids) and Si (as silica and opal phytolithys), are liberated at considerably greater temperatures during thermal decomposition compared to K and Cl ions (Bourke, 2007). Magnesium is bound to organic molecules (through covalent and ionic interactions), therefore it can only be vaporized at very high temperatures (Laird et al., 2009). Some inorganic and organic components in the feedstock (for example, Fe and Mn) are not removed during pyrolysis, and hence end up in the biochar residue. Potassium might be placed on a charcoal matrix, generating phenoxides or intercalating between graphene sheets. Ca, like K, could produce phenoxides in the biochar matrix (Wornat et al., 1995).

             Other mineral elements may be found in the biochar forming various minerals in phases minor. They may include amorphous silica, anhydrite (CaSO₄), calcium phosphates [Ca₃(PO4)₂], calcite (CaCO₃), garnet [Ca₃Al₂(SiO₄)(OH)₈], gonnardite [(Na, Ca)₂(Si, Al)₅O10*3H₂O], hydroxyapatite [Ca₁₀(PO4)₆(OH)₂], quartz (SiO₂), sylvite (KCl), and various hydroxides, oxides and nitrates of Zn, Mg, Mn, Ca, Fe, and Al. Some of these minerals could make biochar manufacture (e.g., amorphous silica creates phytoliths, which cover plant C content from degradation) or applications more difficult (for example, silica crystalline in some biochar is a carcinogen) (Parr and Sullivan, 2005; Smith and White, 2004). (Ndirangu et al., 2019).

2.3.5 Benefits of biochar

     2.3.5.1. In soil properties

The addition of biochar to soil can have a variety of physical, chemical, and biological impacts (Lehmann et al., 2011). According to some authors, biochar can be used as a soil amendment to improve the quality of soils (Lehmann et al. 2003).

   The bulk density, particle size distribution, porosity, structure, and texture of soil are all improved by biochar (Ding et al., 2016; Manya', 2012; Chan and Xu 2012). The use of biochar can help to lower the bulk density of various soils (Chen et al., 2011). This could result in improved soil structure or aggregation, as well as increased aeration and hence improved soil porosity. The surface area of biochar is significantly larger than that of soil (Joseph et al., 2010). Biochar's surface is covered in micrometer-scale pores large enough to hold nutrients, water, microorganisms, and a variety of other substances (Chan and Xu, 2012). Increased water and nutrient retention are explained in part by biochar's huge surface area and porous nature (Barrow, 2012). Fresh biochar's negative surface charge can also attract positively charged molecules like NH₄⁺ (Spokas et al., 2012). If inorganic N is available to crops, adsorption of inorganic N could have potential benefits for fertilizer N use efficiency in agricultural soils. Increased water adsorption could boost moisture retention in a soil system (Karhu et al., 2011).

     Increases in soil CEC and carbon are among the chemical characteristics that are impacted by biochar (Laghari et al., 2016). The majority of research on biochar as a soil supplement has focused on soil nutritional status, taking into account cation exchange capacity, pH, nutrient content, the modified soil's carbon sequestration potential, and crop vegetative development and yield. Because of its negative surface charges and high specific surface area, biochar has the potential to increase soil CEC. This has been documented for biochar made from crop leftovers (Yuan and Xu 2011). Furthermore, as documented for soils supplemented with secondary forest biochar, the initial favorable effect of biochar application on crop productivity in tropical soils may be due to increased availability of nitrogen, potassium, phosphorus, calcium, copper, and zinc (Lehmann et al.,2003). 

     Biochar is a material that has the ability to directly keep macronutrients like nitrogen (Zhang et al., 2017). This can be ascribed to biochar's high nutritional content (Shepherd et al., 2017 and Glaser and Lehr 2019). Biochar can be used as organic fertilizer by supplying nutrients to the soil that were previously present in the precursor feedstock (Gul and Whalen, 2016). However, biochar provides a number of additional advantages for plant nutrient cycling, including improved fertility of the soil and more increased nutrient uptake by plants, as well as increased retention and use efficiency and less leaching (Laird et al., 2010; Randolph et al., 2017). Biochar has been shown to have favorable impacts on soil nutrient mobilization and plant nutrient uptake in numerous studies (Atkinson et al., 2010).

Biochar treatment at low fertility soils improved total C by 7–11 %, P by 68–70 %, K by 37–42 %, and Ca by 69–75 % compared to no use biochar according to Laghari et al., (2015). Zhang et al., (2017) discovered that using biochar increased the availability of nitrogen (N), potassium (K), and phosphorus (P) at low fertility soils. Biochar treatment not only improved performance and increased soil nutrients of Ca, Mg, and K, but it also raised plant uptake of Ca, Mg, K, and P at the same time (Major et al., 2009). Biochar addition has been proven in many studies to significantly boost soil nutrient content (Laird et al., 2010; Liang et al., 2014). This is due in part to direct nutrient additions, like P and K (Enders et al., 2012), and in part to less leaching and run off (Laird et al., 2010). Brandstaka et al., (2010) compiled a list of biochar's general impacts on soil. They describe it as beneficial for carbon sequestration, improved cation exchange capacity, soil aggregate durability, microbial activity, bioenergy production, and water retention capacity; reduced methane and nitrous oxide emissions from soils, leaching, soil erosion, and fertilization requirements, resulting in improved fertility of soil and crop yields (Brandstaka et al., 2010). Other authors have documented its utility in reducing greenhouse gas emissions (Rogovska et al., 2011; Van Zwieten et al., 2010) and preventing leaching of applied nutrients (Major et al., 2009). Biochar made from green waste by pyrolysis enhanced soil pH and organic carbon, according to Chan et al., (2008).

    Biochar amendment to soil changes the chemical and physical environment, and therefore have an influence on soil microbial community and activity (Grossman et al., 2010; Kavitha et al. 2018). There are several mechanisms proposed by which biochar can influence soil microbes, including the porous structure of biochar which provides a habitat for microbes (Warnock et al., 2007), its effects on plant growth and associated plant C inputs (Major et al., 2010), its source of trace minerals (Rondon et al., 2007), its sorption of microbial signaling compounds or inhibitory plant phenolic compounds (DeLuca et al., 2015), as well as its effect on soil physical and chemical properties. Because the physical and chemical characteristics of biochar provide optimal habitats for microbial communities, including abundance, diversity, mobilization, nutrient acquisition, and cycling, treatment of microbes with biochar should have a positive effect (Lehmann et al., 2011; Quilliam et al., 2013).

      2.3.5.2. Effect of biochar on plant growth

Biochar is typically applied to agricultural areas in order to boost crop output, and there is evidence that this is possible (Schulz et al., 2013). For example, Silva et al. (2020) discovered that when biochar concentration rose, the fresh root, fresh shoot, and dry shoot weights, as well as stem diameter measurements, improved in tomato. Brennan et al. (2014) also reported that the usage of maize biochar increased maize plant development parameters. Similarly, Zhang et al., (2012) discovered that adding charcoal to rice boosted yield by 10% in the first cycle and by 9.5–29% in the following cycles. Agegnehu et al., (2016) found that three repeated treatments of 7 t/ha of biochar through two growing seasons on soils planted to maize boosted maize yield.

Biochar has been found to improve plant growth by delivering nutritious elements to growing plants, as well as enhancing water and nutrient retention capacity (Akhtar et al., 2014). According to (Glaser et al., 2009) biochar's indirect importance, which is its ability to keep nutrients in the soil and hence lessen leaching losses, the positive impact of biochar is attributed to enhanced nutrient uptake by plants and more increased production. Plant development can be improved by using biochar because it increases nutrient availability, microbial activity, water nutrient retention capacity, and bulk density (Lehmann et al., 2006).  

On the contrary, Mau and Utami (2014), discovered that biochar had no influence on plant development. In addition, Graber et al. (2010) found that biochar has no effect on the number of flowers or fruit of tomato plants. Biochar did not significantly boost shoot, root dry weight, or plant height, according to (Mau and Utami 2014). In addition, with incremental additions of biochar in the soil, plant shoot weight reduced from 17.7 to 9.1 g (Kelly et al., 2015).

     Because of the variety of biochar, soils, and fertilizer management strategies employed in trials, it's difficult to compare results between studies. Biochar addition to acid soils, for example, boosts crop production, whereas biochar addition to calcareous soils does not necessarily do so (Liang et al., 2014). Biochar application to low-fertility soils could boost crop yields significantly (Laghari et al., 2015; Zhang et al., 2017). Biochar treatment increases crop productivity most often in nutrient-poor and degraded soils (Laghari et al., 2015), although its impact is not always noticeable in fertile or healthy soils (Hussain et al., 2017). Biochar made from eucalyptus, for example, increased maize yield (Zea mays L.) in deteriorated Kenyan soils by twofold (Kimetu et al., 2008). In a pot experiment, Laghari et al. (2015) investigated the influence of pine sawdust biochar on sorghum (Sorghum bicolor (L.) Moench) development in an unproductive sandy desert soil from China. They discovered that when compared to a control soil with no biochar, the dry weight of sorghum rose by 18–22%. However, Major et al., (2010) found no change in maize production in the first year, but significant increases in the following three years after wood biochar amendment at a single dose of 20 t ha^-1.

2.4. What are Mycorrhizae fungi?

Mycorrhiza is derived from two words Greek: the word myco, which means fungus, and the word Rrhiza, which means root, and its literal meaning is a symbiosis between root and fungus. Mycorrhiza is defined as mutual participation in life, in which the fungus is the primary companion of the plant and is responsible for supplying nutrients, growth hormones, and pathogen protection to the root of plants, while a good plant will provide energy needs to the fungus (Alizadeh, 2011a). Because of their symbiotic relationship with plant roots, arbuscular mycorrhizal fungi (AMF) play a crucial role in vegetation restoration; they can help the host plant absorb minerals, stabilize and enhance soil structure, influence population structure, and retain species variety (Rodrigues et al., 2021). They are important members of the soil biota, accounting for roughly 25% of agricultural soil microbial biomass. Ecto and endo mycorrhizae are the two most common forms of mycorrhizae. An extracellular fungus growth in the root cortex distinguishes ecto mycorrhizae. in the root cortex inter, and intracellular found endo mycorrhizae. Vesicular arbuscular mycorrhizae are the most common type of endo mycorrhizae. It's now known as arbuscular mycorrhiza (AM) (Van Creij et al., 2020).

AMF can be found in soil as chlamydospores or in the rhizosphere as in roots vegetative propagules. Their hyphae entry in the cortex of the root and bifurcation intracellularly from the entry point. The fungus creates an arbuscular within cell cortical, where metabolites are exchanged between the host root plant and the fungus. The vesicles are in the intracellular spaces, which are storage lipid and reproductive structures. While the fungus benefits from the C compounds produced by the host plant, AM fungi carry mineral nutrients and water from the soil to the host plant (Moukarzel et al., 2021).   

AMF can be found in almost all soils about the world, and they develop a relationship with about 80% of all plant roots (Harley and Harley 1987). The favorable advantages of the AMF symbiotic relationship on plant growth are widely established (Smith and Smith 1996 and Lakshman 2009). Arbuscular mycorrhizal fungi aid in plant water control by extending their hyphae into suitable moisture zones for continuous water absorption and translocation to plants. The arbuscular mycorrhizal association has been found to increase the rate of transpiration, photosynthesis, and chlorophyll content in host plants by affecting leaf photosynthesis and stomatal movement (Bethlenfalvay et al., 1988 and Panwar 1991).

Most terrestrial plants have symbiotic relationships with AMF and nitrogen-fixing bacteria, which extract nutrients in the soil and exchange them for photosynthetically fixed carbon from the plants. In actuality, the rhizosphere is a continuous, diverse, and natural ecosystem in which plants and soil microorganisms interact in a variety of ways. The fundamental determinants of soil fertility and plant health are positive plant-microbe interactions in the rhizosphere. Worldwide, efforts are being made to improve nutrient-efficient plants cultivars that respond to bio-fertilizers in order to boost crop output while simultaneously maintaining soil health. Plants are thought to prefer AMF and microorganisms that promote plant growth, like nitrogen fixers. Sustainable agriculture, which utilizes fewer chemical inputs like pesticides and fertilizers that harm soil fertility, health, and the environment, is the current focus (Lakshman, 2007). As a result, the utilization of microbial inoculants is critical in the development of sustainable agriculture. AMF has been shown to increase plant growth, nutrition, and development, as well as protect plants from root infections and provide drought resilience (Jeffries, 1987).

AMF are the most widely distributed mycorrhizal associations, both geographically and among species of plants. The Glomeromycota is a group of fungi that are obligately symbiotic. Although this is most likely right, it is based on analogy with species for whom biology is known. Such species have been shown to have Nostoc (Cyanobacteria) species as symbionts in one case (Schüßler, 2002), or to create an intimate symbiosis with embryophytes (land plants) in all other cases (Schüßler, 2002). AM can also be formed by vascular land plants, hornworts (Schüßler, 2000), and liverworts (Fonseca and Berbera, 2008). Many glomeromycotan species are known to generate AM, but many more have been described from field specimens with no knowledge of the fungus' nutritional condition.

2.4.1. Beneficial Effects of AM fungi:

         According to Muchovej (2002), the positive effects of AM are caused by one or more of the following mechanisms: Root absorption capacity has increased as a result of morphological and physiological changes in the plant. Increased mobilization and transfer of nutrients from the soil to the plant, such as P, N, Cu, and Zn, Antibiotic secretion and community support that competes with or antagonizes harmful bacteria, assisting in disease suppression, increased legume establishment, nodulation, and nitrogen fixing capability in the atmosphere Plant growth hormones such as cytokinins and gibberellins are produced in greater quantities. Modification of the soil-plant-water relationship, allowing plants to better adapt to harsh environmental conditions (drought, metals), Contribute to soil structure by growing external hyphae into the soil to form a skeletal structure that holds soil particles together, allowing the plant's carbon supplies to be directly tapped into the soil (Chen et al., 2018), Uptake of micronutrients, and tolerance and adaptation of plants to heavy metals.

2.4.2. Factors affecting mycorrhizal formation:

2.4.2.1.  Nutrients:

                AM mycorrhizal infection is more common in soils with a moderate or low fertility level. Many studies have shown that high fertilizer levels, particularly P and N, can reduce the percent of colonization of root by AM fungi as well as the hyphae length (Reyes et al.,2019). In greenhouse and field investigations, the reduction of AM colonization with increased P treatment had been well documented (Ikoyi et al., 2018). Padma and Landasamy (1990) also discovered that adding a large amount of P to papaya seedlings reduced the degree of AM colonization.

         Increased phospholipid levels lower membrane permeability and minimize exudation of organic acids, amino acids, and sugars, which are the source of sustenance for germinating mycorrhizal spores, according to Ziane et al., (2021). In well-fertilized soils, the mycorrhizal association may shift from a symbiotic to a parasitic one (Dechassa, 2001). The impact of the host's nitrogen nutrition on AM-mycorrhizal infection has gotten little study. P and N are known to have a deleterious impact on AM infection. It's been claimed that high nitrogen levels in the root have a negative impact on the mycorrhizal infection (Wang and Hayman, 1982). On the other said, Furlan and Bernier-Cardou (1989) found that nitrogen fertilization increased onion plant root colonization and spore production in the soil.

2.4.2.2. Organic matter:

                According to reports, adding organic matter to soil farmed with herbage plants treated with cow and pig slurries reduced AM root colonization and fungal hyphae growth (Christie and Kilpatrick, 1992). Green manure had a deleterious influence on the potential of mycorrhizal inoculums in monoculture barley, but not in rotation (Baltruschat and Dehne, 1989). Werner et al., (1990) investigated strawberry root mycorrhizal colonization in conventional and organic management regimes. Root colonization was modest in both systems in the first year, but higher in the transitional organic plots in the second year. Ryan et al. (1994) studied AM colonization of wheat in two nearby farms, one using a conventional agricultural system and the other using an organic farming system. The percentage of AM colonization in wheat inorganic farmed plants was 2-3 times higher than in conventionally farmed plants. They went on to say that decreased colonization levels in the conventional farm were related to the continued use of soluble phosphorus fertilizer in glasshouse and field studies. They also discovered that utilizing rock phosphate fertilizer on an organic farm had little effect on AM colonization levels. On the other hand, Green manure had a favorable effect on plant mycorrhizal inoculum potential (Ortiz-Salgado et al., 2021).

2.4.2.3. Plant genotype:    

As a result, genetic differences across plant cultivars can have a significant impact on the symbiosis between the host roots and AM fungus, as well as the proportion of AM infection (Mateus et al., 2019). The percentage infected with AM varies according to the host species, according to Jakobsen and Nielsen (1983). They discovered that in cereal crops, the fraction of root length infected with AM was 50%, whereas, in peas, it was 75%. Krishna (1986), on the other hand, discovered a wide range of mean mycorrhizal colonization in Peal millet genotypes in three field locations. The percentage of plants colonized ranged from 25 to 56 percent, demonstrating that mycorrhizal colonization is genotype-dependent. When barley cultivars were grown in soil without P supplement, Baon et al. (1993) discovered that mycorrhizal infection ranged from 8.6% to 28.6%.

2.4.2.4.  Metals:

Metal availability and toxicity to mycorrhizal fungi and plants depend on metal concentrations and soil and rhizosphere pH, oxidation states, soil cation exchange capacity (CEC), organic matter content, texture, and redox potential (Meharg and Cairney, 2000 and Liu et al., 2000). Metals are sequestered by fungal hyphae, which may help to minimize metal transport into and toxicity in the host (Zhuo et al., 2020). Several biological and physical mechanisms have been proposed to explain the generally lower metal toxicity to plants colonized by arbuscular mycorrhizal fungi. These include adsorption onto plant or fungal cell walls present on and in plant tissues or onto extraradical mycelium in soil (Souza et al., 2020). Also, Javeria et al., (2017) chelating by such compounds as siderophores and metallothioneins released by fungi or other rhizosphere microbes, and sequestration by plant-derived compounds like phytochelatins or phytates (Joner and Leyval, 1997). Other possible metal tolerance mechanisms include dilution by increased root or shoot growth, exclusion by P recipitation onto polyphosphate granules, and compartmentalization into plastids or other membrane-rich organelles (Vilela, 2021).

2.4.2.5.  pH:

                Some AMF weak at soils low-pH, whereas others weak after acidic soils were limed (Davison et al., 2021). Plants that formed associations with AMF boosted plant development in limed acid soils (Liu et al., 2020a), but in other acid soils, a positive AM fungal effect was discovered without the requirement to elevate pH (Guzman-Plazola et al., 1988). Plant productivity is improved by arbuscular mycorrhizal fungi, which increase nutrient uptake, notably of P. (Clark et al., 1999). Some studies believe that AMF tolerates low external pH by changing the pH of the mycorhizosphere through the uptake process. It's possible that the effect of soil pH on AMF and inoculated plants are dependent on the variance between the pH of the soil from which the fungus was obtained and the pH of the experimental system under study (Pacovsky, 1986).

2.4.2.6.  Effect of water regime:

When inoculated with Glomus macrocarpium, Radwan (1987) discovered that shoot growth of mycorrhizal cotton (Gossypiumbarbadens L. cultivar Giza 77) attained a maximum at a 55% water regime. Radwan (1987) also discovered that plants of Giza 70 fertilized with monocalcium phosphate (MCP) demonstrated a favorable effect of AM on growth in water regimes of 20% at 30°C and 55% and 90% at 35°C. Simpson and Daft (1990) found that soil water stress reduced maize and sorghum plant growth, and that mycorrhizal infection by Glomus clarum, Glomus monosporum, and A caulospora spp. had no effect on this reduction. However, the percentage of AM infection is unaffected by water stress and is unrelated to plant growth.

2.4.2.7.  Effect of salinity:

                AMF are found naturally in most soils and can help numerous agronomic crops grow better in infertile soils (Wang et al., 2018a). Researchers have paid little attention to the presence of AM in saline soils and its impact on plant development and nutrient uptake. In calcareous (Read et al., 1976), salt-affected soils (khan, 1974), and salt marshes, halophytic and non-halophytic plants are frequently mycorrhizal (Nicolson, 1960; Sengupta and Chaudhuri, 1990). AM enhanced onion and pepper yield and salt tolerance in salinized soil, according to Hirrel and Gerdemann (1980). Because non-mycorrhizal plants with additional P in saline soils grew as well as mycorrhizal plants without P additions, the mechanism of salt tolerance boosted P nutrition (Chandrasekaran et al., 2019).

2.4.2.8.  Effect of soil temperature:

Temperatures of at least 25°C promote arbuscular mycorrhizal infection significantly (Bennett and Classen, 2020). With Endogonegigantea, Schenck and Schroder (1974) reported maximum arbusculer formation in soybean (Glycine max, L) root at 30°C. The optimum temperature for mycelia development on root surfaces was 28 to 34°C, whereas the optimum temperature for sporulation and vesicle development was 35°C. Davison et al., (2021) discovered that mycorrhizae plants responded strongly to temperature changes, with a steep rise from 20 to 30 ° C. and a steep decline from 30 to 35°C. Mycorrhizae plant growth was closely tied to phosphorus uptake, which was significantly higher than that of non-mycorrhizae plants.

Glomus margarita root colonization and cotton growth were highest at 24 and 30°C, with little fungus or host development at 14 and 19° C, according to Hussey and Roncadori (1981). The effects of six species of AM fungus on soybean growth were explored by Schenck and Smith (1982). For most species, optimal fungal colonization and sporulation occurred between 24 and 30°C. Glomus mosseae was found to enhance solely plant growth. In Eupatorium odoratum L. inoculated with G macrocarpus (Goethingen strain), Saif (1983) discovered that infected root length and number of vesicles rose as temperature (and soil oxygen level) climbed from 20 to 30°C, whereas arbuscular growth reduced above 25°C. According to Hayman (1974), the influence of light varies depending on the soil type.

2.4.2.9.  Effect of soil tillage:

                Ahmed et al. (2000) investigated the colonization of roots by AMF and non-mycorrhizal fungi, as well as nutrients in plant tops grown during a three-year maize rotation in two Switzerland locations where fields had been subjected to three tillage treatments (conventional, CT; chisel ploe, CP; and no-tillage, NT). With NT, mycorrhizal fungi colonized maize roots to a larger extent than with CP or CT treatments.

         Reduced soil tillage improves mycorrhizal colonization of plant roots and boosts plant P concentration (Rosner et al., 2018).  Reduced tillage, by maintaining the hyphal networks in the soil intact, is thought to promote mycorrhizal activity and consequently plant nutrient uptake (Moitinho et al., 2020). Reduced tillage intensity, on the other hand, can impact the amount of organic carbon at the surface (Turrini et al., 2017), phosphatase activity (Deng and Tabatabai, 1997), and the relative abundance of soil fungi (Beare and Stevens 1997; Frey et al., 1999).

2.4.2.10.  Effect of crop rotation:

                Crop rotation has an impact on AMF colonization (Bakhshandeh et al., 2017). Harinikumar and Bagyaraj (1988) investigated the impact of rotating finger millet, mustard, and cowpea crops. They discovered that after growing Finger millet, leaving the soil fallow reduced AMF infection in cowpea roots by 40%, while growing the non-mycorrhizal host (mustard) reduced it by 13%. According to Black and Tinker (1979), the spore number and percentage of infection of barley were highest after barley, but when barley was cultivated after kale plant or fallow, the spore population and infection percentage were lower. In soil previously cropped with a non-host plant, the quantity of AM infection in a host plant was not reduced, even when the roots of the previous non-host plant were left intact in the soil (Ocampo and Hayman, 1981). The non-hosts oilseed rape, cabbage, and sugar beet, respectively, encouraged the early establishment of AM infection in barely, lettuce, and maize inoculated in sterilized soil. When compared to plots previously cultivated with tropical grass, cassava, tropical forage legume, and Sorghum sp., Dodd et al. (1990) found that the percentage of AM infection in cowpea and Stylosanthe scapitata roots was significantly higher in plots previously cultivated with tropical grass, cassava, tropical forage legume, and Sorghum sp. After soybean, the AM infection rates in maize were substantially greater than after fallow (Vivekanamdan, 1990). Crop rotation generated considerable changes in mycorrhizal fungus population, these changes may be engaged in the rotation influence on soil productivity, and cropping methods should take mycorrhizal fungal into mind, according to Paranavithana et al., (2021).

2.4.3. Symbiotic mycorrhizae with plants: 

      The symbiotic interaction of roots with arbuscular mycorrhizae (AM) fungi improves phosphorus delivery to plants, particularly when soil phosphorus supply is limited (Abou El Seoud et al., 2017). In the absence of plants, AM fungus have lost their ability to exist and complete their life cycle. Mycorrhizae, not roots, are the primary organs of nutrient intake by plants, with 90 to 95% of all land plants forming some type of mycorrhizal relationship. The host plant offers soluble carbon sources for the fungus, while the fungus increases the host plant's ability to absorb water and nutrients in the soil (Bago et al., 2000).

          The fungus' hyphae have a radius of about 1.5 Pm and a huge surface area, resulting in an increase in P absorbing surface area, the synthesis of organic acids and phosphates, and the catalysis of P release from organic complexes (Aono et al., 2004 and Wang et al., 2004). Mycorrhizal fungi can also enhance the surface area of plant roots by developing first-order lateral root branches (Aguin et al., 2004). Mycorrhizal fungi spread a network of hyphae many centimeters into the surrounding soil, allowing the plant to use a larger amount of soil (Frank, 2002). External hyphae of mycorrhizal fungi, which are 100 times better than wheat roots and 10 times better than root hairs in uptake nutrients, access sites that are normally not permeable by root hairs or roots, which led to increasing the surface area for nutrient absorption and reducing P diffusion distances, according to Manske et al. (2000). In addition, the length of mycorrhizal fungi's exterior hyphae can be a useful predictor of their relative ability to take up nutrients. P. According to Ortas et al. (2004), P depletion in sorghum treated with AMF extended up to 20 mm from the root surface. P depletion reached up to 10 mm from the root surface without mycorrhizal plants and remained unaltered at longer distances. The hyphal mycelium improves the overall absorption surface of plants treated with AMF, which led to absorb immobile minerals like Cu, P, and Zn in areas beyond the roots depletion zone (Douds et al., 2005 and Grant et al., 2005).

       Furthermore, mycorrhizal hyphae cause a drop in alkaline soils from 8.5 to 7.4 via organic acids exudation by AMF, which solubilize immobile nutrients like P (Giri et al., 2005). Phosphorus can be absorbed and translocated to the host plant by mycorrhizal hyphae from soil outside the root depletion zone, effectively decreasing the distance between P diffusion and plant roots (Chen et al., 2005).

    The concentration of inorganic P inside the hyphae is approximately 1000 times higher than that in soil solution (Gianinazzi-Pearson et al., 1986). The high efficiency of AM hyphae in phosphorus uptake is also due to the storage of polyphosphates in their vacuoles, which may be hydrolyzed in the arbuscular and transported as inorganic P into the host plant across the plasma membrane of cells (Smith and Gianinazzi-Pearson 1988). Mycorrhizal root associations are stimulated by P deficiency in the soil but are suppressed by high P supply (Jones et al., 1990).            

          The most common use of mycorrhizal symbiosis in contaminated sites is to improve plant mineral status due to a lack of accessible mineral nutrients on sites with high heavy metal concentrations (Shetty et al., 1995). In a semi-arid wasteland soil, Bhoopander et al. (2005) investigated the effects of two arbuscular mycorrhizal (AM) fungi, G. fasciculatum and G. macrocarpum, on Cassia siamea shoot and root dry weights and nutritional content. P, K, Cu, Zn, and Na concentrations in AM infected seedlings were considerably greater than in non-inoculated seedlings.

2.4.4. Effect of A-Mycorrhizal fungi (AMF) on plant growth and nutrients concentration in plant:

         Many researchers have studied the role of A-mycorrhizal fungi in boosting plant growth and elemental composition in a variety of plant species (Ortega et al., 2004; Scagel, 2004; Giri et al., 2005; Douds et al., 2005; Grant et al., 2005; and Abou El Seoud et al., 2017). In addition, Afek et al. (1991) discovered that AM fungus inoculation resulted in the maximum fresh weight and yield of onion plants. According to Gurubatham et al. (1989), AM fungi enhanced bulb output from 19.3 t/ha in unfertilized control to 20.0 - 20.5 t/ha in fertilized control. Similarly, Abdalla (1998) discovered that inoculating seeds with mycorrhizal fungus before sowing boosted the total yield of onion bulbs substantially. Hussien and Abou El Seoud (1999) found that inoculation of cotton plants with AMF grew cotton yield/plot by (24.78%) compared to plants without AMF. Plants treated with AMFi usually produce more dry matter than plants non-mycorrhizal (Sato et al., 2021).              

         The enhanced rate of P uptake found in mycorrhizal plants could be due to a variety of factors (Rdwan, 2017). An extensive network of hyphae extends from the root, allowing the plant to explore a larger volume of soil by increasing the surface area of hyphae for greater nutrient absorption; second, it allows hyphae to enter pores in soils and organic matter that root hairs cannot, overcoming the limitations imposed by the slow diffusion of P in the soil. The depletion zone around plant roots, which is induced by plant uptake and the immobile nature of P, is bigger in mycorrhizal plants than in non-mycorrhizal plants, according to (Valentine et al., 2001). Furthermore, mycorrhizal fungus hyphae have a stronger affinity for phosphate ions and a lower absorption threshold than plant roots. Another benefit attributed to mycorrhizal fungus is that they have access to phosphate pools that are not commonly available to plants (Abou El Seoud et al., 2020).

                One mechanism for this access (Vogt et al., 1991) is the physiochemical release of organic and inorganic phosphorus by organic acids via the action of low-molecular-weight organic anions like oxalic acid which can replace phosphorus sorbet at metal hydroxide surfaces through legend exchange reactions, dissolve metal oxide surfaces that sorbs phosphorus, and complex metals in solution and thus prevent precipitation of metal phosphates (Giri et al., 2005). Another mechanism by which mycorrhizal fungi release inorganic phosphorus is via the mineralization of organic matter. This occurs by phosphatase-mediated hydrolysis of organic phosphate (C-O-P) ester bonds. The extra metrical hyphae of some mycorrhizae produce enzymes phosphatase and protease, which can affect organic matter nutrition availability and mineralization (Koide and Kabir, 2000).

      AMF has also, an important role in the uptake of N by plants. AMF    inoculation improved N uptake in several crops such as Medicagosativa (Nielsen and Jensen, 1983), clusterbean (Champawat and Somani, 1990), soybean (Vejsadova et al., 1992), Heveabrasiliensis (Ikram et al., 1992). Also, A-mycorrhiza improved N uptake of several tropical forage legumes and grasses (Saif, 1987). Barea et al., (1989) found that AMF improved modulation and concentration in Medicago sativa, as well as, improve the amount of uptake N in the grass treated with AMF. Glomus macrocarpum raised N content in both Medicago sativa and Trifolium alexandrinum by 24% and 20%, respectively (Patterson et al., 1990). A-mycorrhizas may become important for plant N acquisition, when the major part of the soil mineral N is present as ammonium, which is less mobile because of retained by clay minerals (Nomik and Wahtras, 1982).

          The direct influence of the mycorrhizal condition was responsible for the increased uptake of other nutrients. Experiments with a potassium-deficient soil, for example, revealed that inoculation plants of Griselinialittoralis (an evergreen New Zealand shrub) grew faster and absorbed more potassium than uninoculated plants (Jackson and Mason, 1984). Plant uptake of Cd, Cu, Zn, and Ni by bean and maize was considerably different due to mycorrhizal inoculation, according to Gue et al., (1996). In contrast, multiple studies have found that mycorrhizal maize plants had lower Mn and Fe concentrations and absorption than non-mycorrhizal maize plants (Arines and Vilariño 1989; Kothari et al., 1991 and Koreish et al., 1998). Bean and maize did not benefit from mycorrhizal colonization in terms of Ni uptake.

                Inoculation with A-mycorrhizal fungi resulted in a highly significant rise in the concentrations of N, P, K, Ca, and Mg in cotton leaves, according to Hussien and Abou El Seoud (1999). Furthermore, the data show that inoculation with A-mycorrhizal fungus resulted in a very significant rise in microelement concentrations (Fe, Mn, Cu and Zn). Elwan (1991) in millet plant and Nashwa (1995) in soybean found similar findings. Elwan (2001) found that mycorrhizal inoculation improved the concentration and uptake of phosphorus, potassium, zinc, and copper by ryegrass plants. The most nutrient limiting for growth crops in many regions is phosphorus (P), according to Heydari and Maleki (2014). AMF has the ability to boost soil P levels and decrease reliance on costly fertilizers.

          Mycorrhizal (Glomus ntraradices) inoculation in maize plants increases root architectural characteristics, plant nutritional status, and soil nutrient availability, according to Subramanian et al., (2009). According to Robinson et al., (2014), the treatment VAM considerably boosted root and shoot length throughout the research. The root length of cycocel-treated plants grew longer. It was confined to plants non-mycorrhizal and plants treated with mycorrhizal. It was discovered that the ability of isolates to maintain the plant growth effectively in the case of mycorrhizal seedlings shows a maximum uptake of nutrients, shoot length, high root length, and a high number of leaves under mycorrhizal infection in 30 days of analysis and had a positive effect on the growth at all intervals. Biochemical analysis was carried out to estimate the total chlorophyll, chlorophyll A, chlorophyll B, and Carotenoids contents and it was analyzed to be 9 ±0.5 mg/g, 8.3 ±0.5 mg/g, 3.6 ±0.5 mg/g, 4 ±0.3 mg/g respectively. It was found to be high in mycorrhizal seedlings on the 30th day of examination, indicating that the symbiosis had boosted the nutrient uptake of cultivated plants. Nonetheless, G. fasiculatum was discovered to be the most efficient fungus, with the highest levels of mycorrhizal colonization and physiological parameter stimulation. The length and surface area of the leaves of VAM-infected plants have significantly grown. VAM is primarily involved in the intake of phosphorus, nitrogen, and other nutrients, as well as the exchange of these nutrients for photosynthesis (Smith and Read, 2008).

2.4.5. Response of plants to different AMF species:    

The ability of AMF species to improve plant development varies (Tawaraya et al., 2012). Heidari and Karami (2014) investigated the impacts of two AMF species, Glumus etanicatum and Glumus mosseae, on nutrient uptake, grain yield, and content of oil in sunflower seeds under field circumstances, and found that Glumus etanicatum had the greatest impact on grain yield and these elements in seeds. Abou El Seoud et al., (2017) investigated the effects of three AMF species on the growth of certain vegetable crops grown in calcareous soil. They discovered that Rhizoglomus irregularis (GI) improved the growth and P content of squash and tomato plants, whereas Rhizoglomus macrocarpium (GM) improved the growth and P content of carrot plants when the P level was low.

         Amer et al. (2010) investigated the impact of AMF on common bean growth (Phaseolus vulgaris L.). They discovered that when inoculated with different spices (Rhizoglomus intraradiaces and Glomus macrocarpium), there was a very significant rise in plant growth as compared to the control. Furthermore, the first species of AMF (Rhizoglomus intraradiaces) was more than sufficient compared to the other mycorrhiza species (Rhizoglomus macrocarpium). 

Zaefarian et al. (2011) investigated the influence of AMF on alfalfa growth and the accumulation of nutrients (N, K, P, Cu, Zn, and Fe) (Medicago sativa L.). The efficiency of four mycorrhizal species: Glomus mosseae, G. etanicatum, G. intraradices, and mixed species (combination of G. mosseae, Gigaspora hartiga, and G. fasciculatum) on nutrient uptake in alfalfa was investigated G. mosseae had the most increased efficiency of uptake, translocation, and distribution of N and P and dry matter in It can confirm that different mycorrhizal species have different abilities to uptake and transfer P into the shoot.

Banni and Faituri (2013) investigated the effects of Rhizoglomus macrocarpium and Rhizoglomus intraradiaces on maize development and copper uptake in a calcareous soil that had been contaminated with copper experimentally. They discovered that plants treated with Rhizoglomus intraradiaces had higher mycorrhizal colonization rates than plants treated with Rhizoglomus macrocarpium. Rhizoglomus intraradiaces was more successful than the other two mycorrhizal species in increasing plant dry weight. Mycorrhizal plants collected more copper in their roots, while their shoots saw significant losses.

The use of the AM fungus for bioremediation of contaminated soil results in increased Cu absorption by plants. The comparisons of the two AM fungus species show that Rhizoglomus intraradiaces can protect against potentially harmful Cu and hence play an important role in the bioremediation of Cu-contaminated soils. In a field experiment using a split-plot design, Heidari and Karami (2014) investigated the effects of two different mycorrhiza species, Glumus mossea and Glumus etanicatum, on grain yield, nutrient uptake, and oil content of sunflower seeds, and found that Glumus etanicatum had the greatest effect on grain yield and these elements in seeds. Puttaradder and Lakshman (2015) investigated the effects of four Arbuscular mycorrhizal (AM) fungi in a similar vein. For Brassica juncea (L.), Gigaspora margarita, Scutellospora nigra, Glomus mosseae, and Rhizoglomus macrocarpum were used to increase biomass yield and seed number.

The results revealed variedly with different AM fungi.  Also, they found that mycorrhizal inoculation greatly influence on plant growth, root length, fresh and dry weight of shoot and root, the dependency of Brassica plants to AM fungi and per cent root colonization and spore number was increased, after the inoculation of Rhizoglomus macrocarpum over the three other AM fungal species. Thus, Rhizoglomus macrocarpum the best microbial consortium for inoculating Brassica juncea seeds before sowing to get better seedling vigor and seed number. In contrast, Akay et al., (2016) investigated the effects of various AMF species (Glomus mosseae, Glomus geosporum, Glomus etunicatium, Glomus caledonium) on the root inoculation and plant elemental content of lupin (Lupinus albus L.) and discovered that there was no significant difference between the AMF species.

2.5 Application of vermicompost and AMF

      Vermicompost and mycorrhizal fungi application boosted tomato plant growth, biomass, and nutrient uptake (Ambo et al., 2010). The use of AM fungus in conjunction with vermicompost can improve maize plant development and yield, as well as other aspects of the plant such as cob weight, leaf production, height, and weight (Roychowdhury et al., 2017). This combination of AM fungus and vermicompost can improve root development, mycorrhizal colonization, and nutrient uptake in the soil (Hussain et al., 2016).

            According to Nikkah Naeeni et al., (2017), using vermicompost with mycorrhiza considerably improved growth indices such as plant height, leaf space, and yield. Also, while using vermicompost with varying species of mycorrhizas (Glomus claroideum and Glomus fasciculatum), maize (Zea mays) plant height rose as compared to control (Gutie'rrez-Miceli et al., 2008b). The usage of mycorrhiza and vermicompost together increased the dry weight of shoot and roots significantly (Akhzari et al., 2018). In addition, the total chlorophyll content was increased significantly affected by the interaction between AMF and vermicompost (Shahbazi et al., 2019a). Ghavami et al., (2017) found that combining vermicompost and mycorrhizal inoculation reduces drought stress in Basil. Treatment AMF with vermicompost may result in increased nutrient uptake, accelerated cell division, cell elongation, and consequently increased metabolic activity (Dhayal et al., 2018). The enhanced soil nutrient supply to plants is mostly responsible for the favorable effects of vermicompost with AMF (Van Wyk. 2018). It appears that using vermicompost promotes Vetiver Grass growth and development via improving the mycorrhizae-plant symbiosis (Akhzari et al., 2018). Cavender et al., (2003) previously demonstrated that nutrients in vermicompost enhanced fungal colonization. Earthworms can also increase AMF in the soil (Turk et al. 2006).

            According to the findings (Shahbazi et al., 2019b), the interaction effect between AMF and vermicompost led to increased nitrogen concentration in the shoot compared to control. Vermicompost could supply more N to plants, while AMF could enhance root uptake surface area, allowing plants to use nutrients and water from the soil more efficiently. Furthermore, vermicompost has been shown to boost and plant growth and nitrogen content through enhancing soil structure, improving soil moisture content, enhancing soil microbial activity, and influencing plant growth that stimulates hormone production (Pareek et al., 2016; Naiji and Souri, 2018).

On the other said, the use of vermicompost and mycorrhiza, had no effect on plant development (Hameeda et al., 2007). Sousa et al., (2012) found that the inclusion of organic residues caused negative responses in AM fungus due to the high nutritional content of these materials, the presence of phytotoxic chemicals, the specific composition of the residue, and pathogen pressure.

2.6 Application of vermicompost and biochar

         Many studies have found that using organic fertilizer with biochar can improve plant growth, soil fertility, and carbon storage potential (Schulz and Glaser, 2012; Schulz et al., 2013). Vermicompost and biochar interaction improved the root and shoot dry weight soybean, according to Wathira et al., (2016). Alvarez et al., (2017) found that when Petunia was grown in combinations including vermicompost and biochar, the maximum plant dry weight was achieved. The combination of vermicompost and biochar in soil promoted nutrient retention and plant growth by retaining nutrients like nitrogen (N) and sequestered carbon (C) (Farrell et al., 2014 and Sanchez-Hernandez et al., 2019). Hafez et al., (2021) discovered that combining biochar with vermicompost increased plant growth and yield. In addition, applying vermicompost with biochar mixture improved chlorophyll content, relative water content, stomatal conductance, cytotoxicity, and nutrient uptake while decreasing oxidative stress. Doan et al., (2015) discovered that when vermicompost with biochar combination was used, it resulted in increased yield and growth. Increases in leaf number, plant leaf area, root length, and root and shoot biomass have all been observed as a result of using biochar and vermicompost (Nazarideljou and Heidari 2014).

           The addition of vermicompost and biochar to the soil as organic amendments can improve the availability of N, K, and P in the soil, crop yield, and nutrient cycling (Ramzani et al., 2016). By retaining nitrogenous nutrients in the soil close to the root zone for an extended period of time, biochar application to the soil can considerably improve nitrification (Kaya et al., 2006 and Li et al., 2019a). Furthermore, plants treated with the synergistic application of vermicompost and biochar under the three irrigation levels had the maximum uptake of N, P, and K in wheat compared to the two solo amendments (Gul et al., 2015). This could be explained by the high mineral concentration of biochar put into the soil (Agegnehu et al., 2017). Vermicompost and biochar have significant impacts on soil microbial diversity and abundance (Doan et al., 2014).

      Plants co-fertilization with vermicompost and biochar led to having the most elevated concentration of N, K, P, Fe, and Mn in plants. This could be attributed to vermicompost and biochar increasing soil water, soil organic matter, and nutrient storage capacity. Vermicompost contains a high number of elements that can be available to plants throughout time while retaining nutrients and water (Wang et al., 2017). The organic matter in vermicompost can also help to avoid nitrate leaching and nutrient loss (Souri et al., 2019). Biochar, on the other hand, can improve soil water and nitrogen retention (in the root zone) while reducing mineral and nitrate leaching (Knowles et al., 2011). This can also improve the N condition of plant tissues. Biochar has a large specific surface area, which is mostly used for anionic adsorption (Mukherjee et al., 2013).

2.7 Application of AMF and biochar

        Inoculation with mycorrhizal species and biochar raised the plant's dry weight substantially (brahim Ortaş, 2016). Solaiman et al., (2010) discovered that in wheat grown AMF colonization increased considerably when application the biochar. The addition of biochar promoted AMF colonization and improved crop nutrient availability in low P soils and during dry seasons, according to Blackwell et al. (2010). According to LeCroy et al. (2013), the addition of biochar, mycorrhizae, and nitrogen increased mycorrhizal root colonization in a sorghum bicolor experiment. A positive association between charcoal addition and fungal colonization has also been documented in several other investigations (Rillig et al., 2010; Solaiman et al., 2010 and Vanek and Lehmann, 2015). Biochar boosted mycorrhizal colonization via the sorption of allelochemicals that normally restrict colonization, according to Elmer and Pignatello (2011).

     The use of AMF with biochar had a good effect on the net plant growth and nutrient uptake compared to the control (Jabborova et al., 2021). Hashem et al., (2019) found that when biochar and AMF were applied together, the photosynthetic rate, chlorophyll, relative water content, in chickpea increased significantly under normal conditions. Li and Cai (2021) obtained similar results in maize, demonstrating the considerable increase in photosynthetic rate and chlorophyll content   

       We don't yet know how biochar affects the quantity and physiology of mycorrhizal fungus (Warnock et al. 2007). may be changes in soil nutrient availability, indirect impacts on mycorrhiza through changes in the number of other microorganisms in the soil, adjustment of symbiotic signals between phytobiont and mycobiont, and provision of a home for fungi and bacteria are all possible processes (Warnock et al. 2007). Biochar can also provide a good habitat for mycorrhizae, and a combination of biochar amendment and inoculation of certain mycorrhizae has been shown to boost biomass productivity the most (brahim Ortaş, 2016). The formation of AMF extraradical hyphae, which aid plant nutrient intake, is influenced by biochar (Warnock et al., 2007). The application of AMF with biochar was a favorable effect on the leaf length, leaf number, and plant dry and fresh weights compared to the control. Li and Cai (2021) reported that AMF and biochar together improved the plant growth of maize. like results were found by Budi and Setyaningsih (2013).

          On the other said, Warnock et al., (2010) found that applying biochar at various rates led to reduced AMF root colonization% and extraradical hyphae. However, not all research has found a link between biochar amendment and AMF colonization. In the ash compartment of biochar, certain elements, like P and K, which are not volatilized during the pyrolysis process, might be relatively high. P levels that are too high may inhibit the formation of mycorrhizal hyphae (Grant et al., 2005). Biochar may also contain high alkalinity (pH > 9), which inhibits hyphae colonization. By reducing nutrient availability or producing unfavorable nutrient levels in the soil, biochar can also inhibit mycorrhizal colonization (Grant et al., 2005). According to Wathira et al., (2016), biochar's ability to adsorb signaling chemicals and function as a sink could reduce mycorrhizal fungi's ability to colonize plant roots. Permanent signal molecule removal from soils could result in a net reduction in the amount of signal molecules reaching mycorrhizal hyphae and spores, resulting in decreased hyphal development and spore germination, and eventually, fungal abundance. Furthermore, Biochar has the potential to adsorb chemicals that are harmful to mycorrhizal fungi (Warnock et al., 2010).

2.8 Application of vermicompost, Biochar and AMF

Application of vermicompost, mycorrhiza, and biochar improves soil biological properties, enhances the availability of nutrients to plant roots, and consequently increases plant growth and yield. Therefore, vermicompost, mycorrhizal, and biochar can be an alternative and efficient nutrient source for organic tomato production in the greenhouse (Ardakani and Sharifi, 2017). Njunge, (2018) found that biochar and vermicompost application increase colonization of roots soybean by mycorrhizal and increased growth parameters. Also, the application of vermicompost, mycorrhizal, and biochar of medicinal pumpkin (Cucurbita pepo L.) increases plant growth (Khajeh Haghverdi et al., 2018). Zaefarian, et al., (2019). showed that the use of vermicompost, biochar, and mycorrhizal was more effective to increase number of leafs, stems, and total dry weight. Cataldo et al., (2021) found that using vermicompost, biochar, and AMF led to increased plant growth. According to Zarei and Barati (2017), organic matter, charcoal, and mycorrhizal were more successful in increasing corn production and nutrient uptake.

          Biochar application boosted soil enzyme activity, according to Ouyang et al. (2014), since biochar increased accessible nutrients in the soil and increased soil dissolved organic C and microbial activity and AMF. They also discovered that soil enzymes and C mineralization rate have a linear connection. The augmentation of C mineralization as a result of the administration of organic amendments was also found by Watts et., (2010).