Introduction

Mushrooms cultivation is a successful agricultural industry and global production has increased in the last decade [1]. Mushrooms are grown using natural resources from agriculture, forestry, livestock, and manufacturing industries around the world [2]. The mushroom industry is one of the largest solid waste recycling and fermentation industries in the world [3]. It is projected that the mushroom industry could produce more than 100 million tons of SMC globally by 2026, up from approximately 64 million tons in 2018 [4]. The vast quantities of SMC produced—currently considered waste with little intrinsic value—pose a significant challenge to mushroom growers, who must find suitable disposal sites and pay for the costly transportation of a heavy, low-density, highly moist material. In addition, drying fresh SMC is an extremely energy-intensive and impractical process. Furthermore, the handling and disposal of SMC poses a major environmental risk because it releases greenhouse gasses into the atmosphere through natural anaerobic digestion (which often occurs in the piles created during temporary storage), foul odors, and leachate drainage that contaminates and eutrophicates water receptors depleting dissolved oxygen [5]. The amount of SMC produced in the mushroom industry requires effective management [6]. In most cases, SMC is left discarded or abandoned after the mushroom harvest which raises environmental and health concerns due to the difficulty of managing SMC [7]. Furthermore, this method of landfilling is prohibited by the EU Council Directive. This is because SMC is bulky, and has a water content more than 60% which leads to environmental pollution if left untreated [8]. This in turn threatens the growth of the mushroom industry.

SMC is free of pests and weed seeds due to the high temperatures used in the pasteurization and composting processes as well as the high temperature treatment after harvest. It can be used as a mulch to help control weeds by its mere physical presence and its phytotoxic effects. The SMC is already being used in horticulture as a component of potting mixes, as a soil amendment to enhance wetland grasses in for the remediation of polluted water [9], as a stabilizing agent for severely damaged soils, as animal bedding, and as a tool for the management of plant diseases. In addition, SMC can be successfully used as a matrix for bioremediation of polluted soils [10], as a substrate for vermiculture, or to enrich soils in agricultural or landscape applications. It can replace peat in a soilless culture when applied in the right proportions with discarded mushroom debris [11]. Overharvesting and overexploitation lead to environmental degradation and unsustainable development due to increased CO2 levels from aerobic decomposition of peatlands. Most of the countries in Northern and Central Europe where peat is mainly extracted have been forced to impose mining restrictions to stop environmental damage, peatland depletion, and wetland destruction [12].

Water holding capacity, total pore space, and bulk density are the most important physical properties to consider when using SMC as a growing medium for vegetable crops. Pure SMC without any compost has the highest bulk density and the value decreases with the addition of other materials. The bulk density criterion of an optimal growth substrate should be 0.4 g/cm3, which, as a good measure of porosity allowing free gas exchange through the media, indicates that the ideal water-holding capacity and total pore space are between 50–60% and 70–90%, respectively [13]. The ability of used mushroom compost to bind mineral particles together improves soil structure, aeration, and water-holding capacity [14]. Due to its organic matter content and ability to hold both water and nutrients, SMC can be used as a soilless medium [15]. SMC is a great soil amendment with essential nutrients; therefore, it can be used for various agricultural crops. For every kilogram of mushrooms produced, about 5 kg of spent mushroom compost (SMC) is generated from button mushroom cultivation, of which 3 kg comes from the substrate and 2 kg from the casing soil, while 3 kg of straw-based substrate is generated from oyster mushroom cultivation [6]. Due to overharvesting and the fact that peat is a non-renewable resource, it is becoming increasingly scarce and economically unfeasible [12].

The chemical properties include pH, salinity, electrical conductivity (EC), and others. The ideal pH depends on the type of vegetable crop grown, while the ideal value of salinity and EC is 4 dS/m [13]. The use of SMC in agriculture reduces the amount of biodegradable waste sent to in landfills and converts it into commercially viable agricultural commodities [16]. In addition to enhancing soil microflora and biological activity, SMC is a rich source of organic matter and a vital supply of micro- and macro-components for plants. In addition, SMC is non-toxic to food crops because no chemicals, whether pesticides or fertilizers, are used in mushroom cultivation. Therefore, the SMC could be used as a soil conditioner or an organic fertilizer in their cultivation [16].

The overharvesting and overexploitation of peat leads to environmental degradation and unsustainable development due to increased CO2 levels emanating from aerobic decomposition of peatlands. Most of the countries in Northern and Central Europe where peat is mainly extracted have been forced to impose mining restrictions to stop environmental damage, peatlands depletion, and wetland destruction. These concerns ensure sustainable use of peat resources and responsible use of wetlands. The use of SMC as a growth medium is a sustainable venture into alternative high-quality, low-cost media options. The incorporation of SMC has been found to significantly increase the yield of various crops, according to Muchena [12], who also notes that SMC is an efficient soil amendment and conditioner.

Spent mushroom compost can potentially be used to improve plant growth, crop yield, soil health, organic matter, and nutrient levels, as well as to suppress soil-borne diseases. An integrated management strategy could be used to reduce the severity of the pathogens because SMC contains high levels of organic matter and salts, in addition to various nutrients and enzymes that make it a suitable habitat for various microbes, including fungi and bacteria. These microbes work together to suppress diseases and promote plant growth [17]. It is observed that using SMC as a soil amendment shows positive and significant effects on growth parameters of crop production and plant promotion and induces microbiostasis. The diseases suppressing properties of SMC depend on various factors, including microbial population dynamics, microbial activity, nutrient concentrations, and other supplementary physical and chemical factors [17]. In addition to reducing the need for fungicides and inorganic fertilizers, SMC has the potential to significantly improve the quality of contaminated soils. By saving money on fertilizer costs, SMC also conserves soil.

While the availability of food has increased through the use of fertilizers and pesticides, their widespread use has negative impacts on both the environment and human health. Therefore, it is crucial to implement sustainable agronomic techniques, such as the development of innovative, affordable, and environmentally friendly pesticides, fertilizers, and soil conditioners. According to this strategy, the physical properties of SMC, together with its high bioactive chemical content and easily accessible macro and trace elements, make it a viable option for several agricultural applications. Thus, the purpose of this analysis is to examine how SMCs from different sources are used as growth media in the production of different vegetables and as a tool for regulating crop diseases (Fig. 1).

Fig. 1
figure 1

Scheme for production, recovery, and treatment of SMC

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Materials and methods

Electronic databases

A comprehensive screening of the relevant literature was carried out by analyzing the databases from BMC Springer, Elsevier, MEDLINE, Embase, Ovid, and Web of Science to identify unique studies on the practical applications of SMC in vegetable cultivation and control of crop diseases. [18].

The screening criterion and the review question

A review question was developed to simplify the use of the search parameters. To decide whether the study should be included, the authors independently assessed only original study abstracts and English research titles using a review question [19]. The study technically included all research on the practical applications of spent mushroom compost in cultivation of vegetables and disease management. Titles and abstracts that were deemed suitable by independent writers and satisfied the basic requirements were selected for full paper evaluation. These papers were then used to supply the crucial analytical data for the current analysis. Authors had to be independent when choosing whether to use the recruited papers to minimize possible bias issues [19].

Results

Characteristics of spent mushroom compost

Spent mushroom compost is the residue left over after mushroom cultivation. Generally, SMC contains cereal straw combined with peat, chicken manure, soy protein, gypsum, and urea, which is essentially the substrate for growing mushrooms. The discarded mushroom substrate produced by the mushroom industry comes in two primary varieties: Agaricus bisporus (SMC-AB) and Pleurotus (SMC-P). Agaricus bisporus requires substrates rich in nitrogen and polysaccharides for growth, while Pleurotus can grow on lignocellulosic substrates. Unlike SMC-P, which contains only fermented cereal straw and inorganic nutrient and pesticide residues, SMC-AB consists of a composted mixture of cereal straw and manure (pig, horse, or poultry slurry), calcium sulfate, soil, and other components. In addition, button mushrooms SMC contains a casing layer made up of low peat moss and has a component containing CaCO3 to balance acidity. It is the top layer, several centimeters deep, from which the button mushrooms grow. The growing substrate used in SMC consists of a lot of mushroom mycelium, which is also present. Typically, huge or damaged unharvested mushrooms are also part of the SMC.

Before weathering, SMC typically contains 1.9:0.4:2.4% NPK, and after 8−16 months of weathering, it typically contains 1.9:0.6:1.0% NPK. While potassium is more soluble than nitrogen and phosphorus, it loses a considerable amount of its contents during weathering. SMC cannot be classified as a hazardous material since it contains significantly less heavy metals than sewage sludge [20]. The organic matter contents (volatile solids) gradually decrease due to weathering; weathered SMC differs from fresh SMC in several ways: except for boron, zinc, calcium, and copper, the SMC obtained from several commercial sites shows that the conductivity and pH are continuously high, and the coefficient of variation is less than 25%. The conductivity of the SMC acquired from different sources typically ranges between 1.9 and 8.3 mS/cm−1. On the other hand, fresh SMC can have a Cl content of 1.5 to 7.5 kg t−1. With time, there is a corresponding decrease in the volume of the SMC. The density of the fresh SMC obtained from multiple sources varied from 0.15−0.24 g cm−3 to 0.198 g cm−3 [20].

Different SMCs show different pH and moisture contents but they have generally weak acidic pH (6.7) and low water content (20%). However, the moisture content of button mushroom SMC is significantly higher because of irrigation during cultivation. The C/N ratio, protein, ashes, fibers, and lipids, and dry matter of SMC was 41.74, 3.61%, 6.02%, 62%, and 0.54% (w/w), respectively, in a relevant study [21], that investigated Pleurotus eryngii SMC. The same source reported that C, H, and N levels of SMC dry matter were 59.59%, 7.93%, and 1.64%, respectively.

Sun et al. [21] reported that SMC contains several macroelements including Ca, Mg, K, Na, N, and P. Microelements are also present; the levels of Mn, Zn, and Fe among other elements are within the recommended levels according to EU regulations. High levels of heavy metals have a negative impact on plant growth; however, the values found are well within the advised range, thus it should not be a cause for concern when used on land.

General application of SMC in the cultivation of different vegetable crops

Calcium, nitrogen, ash, and protein build up the majority nutrients and components of SMC, thus validating its use as fertilizer [22, 23]. Several research [22,23,24] showed the viability of SMC in horticultural applications, either on its own or in combination with other materials. Due to their high nitrogen content, SMCs have the potential in soil fertility management [25]. SMC can change structural processes of the soil by accelerating pesticide decomposition [26]. For instance, based on its physicochemical properties and biological activity in pesticide breakdown, Lentinula edodes SMC can act as a soil mulching material [27]. Phosphorus is a key nutrient in plant growth; therefore, SMC can be beneficial as an additive of easily soluble P for soils besides mulching [28]. SMC can be used on agricultural lands to improve soil nutrient content and organic matter [29]. A study shows that a 42-day mushroom incubation period can greatly increase the amount of mineral nitrogen in the soil. It contains a lot of organic and vital plant nutrients, which makes it a good mulching and soil-improving substance [23].

However, as determined indirectly by electrical conductivity (EC), fresh SMC typically has a high salt concentration and high salinity, which is mostly caused by its high calcium, sodium, potassium, nitrate, and ammonium ion content [30]. Therefore, the use of fresh SMC as a growth medium for salt-sensitive plants is not advised; this limits SMC use in agriculture. Thus, before using SMC as a soil amendment, extra processing that involves sufficient decomposition is often carried out.

It is advised to compost organic resources before utilization to boost nutrient availability and decrease the C:N ratio. The organic material decomposes slowly and the soils have low nutrient, using SMC can cause pentosane effect [31]. The electrical conductivity (EC) of SMC is typically higher than 4 dS/m which is higher than that of the soils. The electrical conductivity of a saline is at least 4 dS/m, according to the most common definition [31]. Accumulation and transport of nutrients, cell growth, cell division, photosynthesis, and other physiological activities of plants are all negatively impacted by increased salt content of soils. To modify osmotic pressure in plant cells, the effect of active ions, soluble carbohydrates, and amino acids like proline can be additive. Osmotic adjustments can reduce turgor pressure, manage cellular growth and expansion like stomatal aperture, photosynthesis, and water flow in drought stress [31].

The salinity of SMC can reduce through leaching or long-term weathering. In the first year of weathering, most of the salts that were initially bound in the SMC are released. The primary ions in leachate include potassium (K+), sodium (Na+), calcium (Ca2+), chloride (Cl−), sulfate (SO4−2), and (NO3−) [32]. According to Stoknes et al. [33], a substrate made from perlite and Agaricus bisporus SMC in a volume ratio of 2:1 or 1:2 has good physical and chemical characteristics, water retention, pH, EC, and other indicators. The complex substrate produced high-quality lettuce seedlings with more and bigger leaves, a taller plant, a stronger stalk, more side roots, and higher biological value. It can be promoted in the soilless production of plants based on the trial findings [33].

The pH is consistently high when SMC is used as a substrate component for potted plants without soil. The EC rises as nutrients are released during the first 6 weeks of composting. In addition, the water-holding capacity is increased. After 6 weeks, the biological activity of the compost decreases, and the compost is considered ready to use both by the Solvita and the radish seed test. Successful plant production can be achieved using different types of SMCs, but the optimal plant development requires knowledge of the SMC [34].

According to the study of Grujić's et al. [35], using SMC substrate in the production of potato seedlings showed significant benefits. The SMC substrate primarily consisted of Pleurotus ostreatus medium along with organic and chemical fertilizers as supporting materials. The study suggests that replacing vermiculite and peat moss with SMC can result in an ideal substrate [36].

Numerous studies [37,38,39] have utilized SMC as a biofertilizer for cultivating plants such as lettuce, tomatoes, and pineapple. It was found that the addition of pig manure to SMC can enhance its NPK content, making it suitable as a multifunctional fertilizer [40]. Furthermore, the enzymatic saccharification process for creating biofertilizers could be enhanced by alkaline pre-treatment of SMC [41]. Alvarez-Martin et al. [26] observed significant variations in yield when different crop species were grown on soil treated with Agaricus bisporus and Pleurotus spp SMCs. However, the application of SMC-treated soil resulted in increased plant yield, in comparison with untreated soil. Zhang et al. [13] found that SMC-treated soil yielded higher quantities of tomato and cucumber than on untreated soil. This suggests that SMC had a beneficial impact on vegetable growth. In addition, SMC was utilized in replacing mineral fertilizers. When maize was supported by SMC use, the grain yield was 11.5% higher than that of untreated maize. These results suggest the potential of SMC for usage as a micronutrient fertilizer. In addition, SMC can be transformed into a micronutrient fertilizer through a bio-sorption method, which has improved soil quality, structure, and sorption capacity [42].

Using SMC in agriculture not only turns biodegradable waste into commercially viable agricultural products but also minimizes the amount of organic waste dumped in landfills. Incorporating innovative formulations of SMC has the added benefits of reducing manufacturing costs and the environmental impact of waste management. In addition, more research is required to identify new biological material drying techniques and new biomass species for the manufacturing of micronutrient fertilizer components. The portfolio of new micronutrient fertilizer products is expected to grow in the future, which will contribute to the reduction of production costs [43].

Utilization of SMC to control crop diseases

Farmers generally apply chemical-based products to prevent the infection of plant pathogens. Despite being successful, chemical plant disease management technologies induce significant health and environmental concerns [44]. These chemical pesticides are also costly, non-biodegradable, and their frequent use encourage the development of chemical-resistant disease strains [45, 46]. These products not always satisfy the demands of health conscious consumers, who prefer organically produced food crops. New regulatory restrictions encourage researchers to investigate cutting-edge approaches toward plant health, such as using microbial inoculants and organic composts to reduce pest populations and maintain soil health and fertility [47]. Biological insecticides and living organisms are potential candidates to substitute chemicals in plant protection. In contrast to chemical pesticides, biocontrol agents do not have hazardous leachates that persist over time and the resistance is avoidable as well. They also have minimal effect on non-target populations. They frequently have a shorter shelf-life and low-medium efficacy [5, 48]. On a large scale, microbial-based inoculants, such as Trichoderma spp., are successfully used as biocontrol agents (BCAs) for the pathogen control of fungi such as Chondrostereum purpureum, Fusarium oxysporum, Rhizoctonia solani, and many other soil-borne microbes [49, 50].

SMC can play an important role in the soil as a soil conditioner. SMC offers various advantages in agriculture, including providing plant nutrients, enhancing soil structure, increasing the availability of plant nutrients, promoting soil microbial diversity and populations, improving soil cation exchange capacity, enhancing soil aeration, optimizing plant root structure, improving soil water-holding capacity, regulating soil pH, and reducing soil compaction [55] through enhancing water and air porosity. Consequently, SMC is suitable for agricultural use, indirectly contributing to the modification of disease resistance in plants [52]. The SMC also contains a diverse microbiota that can maintain the balance needed to guarantee crop health during cultivation. Moreover, some types of beneficial microorganisms may be able to enhance the resistance of seedlings against diseases as a result of having been germinated in SMC substrate [52].

Application of SMC could serve as an integrated disease management strategy to reduce the severity of the pathogens. SMC contains antagonistic microbial communities and organic material, as well as enzymes and other nutrients that make it an appropriate environment for microbial populations, including fungi and bacteria to thrive. These microorganisms work synergistically to suppress disease and promote crop growth [53]. It is observed that compost as an organic amendment demonstrates significant and beneficial impacts on growth parameters of the crops. The microorganisms protect plants against diseases by stimulating microbiostasis, direct toxicity, e.g., by releasing ammonia or by inducing systemic resistance. These effects are attributed to microbial population dynamics, microbial activity, nutrient levels, and other related physical and chemical aspects.

The use of bio-based products for boosting crop yield, soil fertility, and for avoiding plant protection issues in sustainable farming is strongly encouraged. This can reduce the application of chemical-based products and their related negative environmental effects. Silicon, which is present in SMC created from paddy straw and other straw wastes from various cereals, is known to be essential for plant metabolic processes, to boost host tolerance, to improve microbial interaction, and to stop pathogen colonization. These characteristics support the possibility of Si-rich SMC to function as an efficient biopesticide and biofertilizer. Extracts from SMC can inhibit the growth of plant diseases through antagonistic processes, such as parasitism, antibiosis, competition for space and nutrients, the induction of plant resistance or through suppressive physio-chemical mechanisms [56].

Mehta et al. [53] found that organic waste (feedstock) compost as a growth medium resulted in a 20%–90% suppression of pathogens. Wang [57] reported that SMC treatment significantly reduced Fusarium oxysporum f. sp. cucumerinum fungal optimal culture (FOC) abundance and Fusarium wilt disease in cucumbers. These findings are in line with earlier research [54] that indicated lower F. oxysporum f. sp. radicis-lycopersici disease incidence in tomato, when Agaricus bisporus SMC was applied. In addition, according to Chen et al. [51], blewit mushrooms compost could prevent Pythium aphanidermatum infection, subsequently reducing the frequency of cucumber Pythium damping-off. In addition, SMC contains active mycelium that can inhibit the development of Fusarium oxysporum f. sp. Cubense (FOC) in vitro more effectively, compared to typical organic compost. Similar to this, numerous studies found that the combination of bio-organic fertilizers and biocontrol agents has a greater inhibitory impact on soil-borne microbes than the substrates alone [58]. Cucumber dry weight, root length, root dry weight, and plant height were considerably higher than those in the control group. In another study, spent Flammulina velutipes substrate greatly accelerated cucumber seedling growth [13].

Gea et al. [59] reported that SMC teas significantly inhibited dry bubble (caused by Lecanicillium fungicola) infection. When compared to the standard fungicide control (Prochloraz at 50 ppm), the SMC tea performed better in terms of disease control and total yield. Kang et al. [60] reported a 65% suppression of Phytophthora capsici, the pathogen that causes Phytophthora blight of pepper. Yusidah and Istifadah [61] examined the efficiency of SMC obtained from oyster (Pleurotus ostreatus), straw (Volvariella volvaceae), and shiitake (Lentinula edodes) against F. oxysporum f. sp cepae, the causal agent of basal rot disease in shallot. They found that the SMC significantly decreased the severity of the disease by 44–76,8%.

Kwak et al. [62] examined the effects of water extracts of SMC from Hypsizygus marmoreus, Lentinula edodes, Hericium erinaceus, and Grifola frondosa, against bacterial pytopathogens causing diseases in various food crops. These pytopathogens included Agrobacterium tumefaciens, Pectobacterium carotovorum subsp. carotovorum, R. solanacearum, Xanthomonas oryzae pv. oryzae, X. campestris pv. campestris, X. axonopodis pv. vesicatoria, X. axonopodis pv. citri, and X. axonopodis pv. glycine. Using quantitative real-time PCR, it was discovered that H. erinaceus SMC water extracts enhanced the expression of plant defense genes encoding 1,3-glucanase (GluA) and pathogenesis-related protein-1a (PR-1a), linked to systemic acquired resistance. In addition, the extracts increased tomato plant growth in all aspects (leaf number, plant height, and shoot and root fresh weight) and inhibited R. solanacearum-caused tomato wilt disease by 85% in seedlings. These findings imply that the antibacterial activity, plant growth promotion, and induction of defense gene activity of the water extract of H. erinaceus could control the bacterial wilt disease of tomato. The most pertinent studies on using SMC to control crop diseases are shown in Table 1.

Table 1 Different diseases managed using extracts from SMC obtained from different mushrooms
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Parada et al. [63] reported that extracts from Pleurotus eryngii and Lyophyllum decastes SMCs were effective against fungal and bacterial pathogens of cucumber. The pathogens were Podosphaera xanthii, a fungal pathogen that causes powdery mildew and Pseudomonas syringae pv. lachrymans, a bacterium responsible for angular leaf spot on cucumbers.

Integration of SMC into tomato production technology

The compost derived from mushroom cultivation can be utilized as an organic fertilizer [2]. However, it is important to note that the compost may not be completely stable under certain conditions, high EC caused by excessive amount of salts, poor physical quality, the presence of heavy metals, or high moisture content under storage can ruin its stability. Nevertheless, when produced appropriately, spent mushroom compost offers several advantages, including a rich microbiota that helps fulfilling the phytosanitary requirements of plant cultures [64, 65]. In addition, SMC contributes to fertility and plant nutrition as well [66].

The microbiota in the rhizosphere region may be significantly regulated by the microbial community of the SMC. This medium is a significant source of microorganisms of various kinds that could foster disease resistance. Different mushroom species produce biotic resistance inducers, which are chemicals that cause plants to respond defensively [38]. Moreover, composts enhance the growth of plants through the production of plant growth regulators which can suppress plant diseases [67]. Fusarium wilt caused by the soil-borne fungus Fusarium spp. is one of the most devastating diseases of most plants including tomato and pepper. SMC showed a significant suppression with Fusarium spp. which further decrease the plant diseases in seedling and subsequent field [67]. Therefore, SMC may be considerably more beneficial than using it as a simple organic fertilizer or soil conditioner [42].

Pleurotus ostreatus and Agaricus bisporus SMCs were used as seedling medium of various vegetable species, in the study of Medina et al. [68]. The A. bisporus SMC-enriched medium performed better than that with added P. ostreatus SMC; however, peat (control) demonstrated significantly better results compared to any treatments containing SMC as a growing medium for tomato seedling development. Lopes et al. [38] applied Agaricus subrufescens SMC, which performed worse, than the 100% Bioplant control media. A. subrufescens SMC was used to raise tomato seedlings in a range of ratios (0 to 100%); seedling performance was evaluated before and after transplantation. The comparison of the SMC and the commercial substrate in terms of root mass and shoot mass showed no outstanding advantage of the application of SMC. In contrast, the seedlings grown in SMC substrate showed higher agronomic performance. Regarding the total amount of tomato fruits produced, the greater the SMC percentage employed, the higher the tomato yield was; the highest results were found in the case of the substrate containing 100% SMC.

Meng et al. [69] reported that the bulk density of media supplemented with SMC was under 0.4 g/cm3 which provides ideal gaseous exchange in the growth media. Other authors [13] investigated Agaricus bisporus and Pleurotus ostreatus SMC supplemented to 20–30% level. They reported that due to the comparatively optimal air porosity, leaching was less likely, and the substrate demonstrated excellent water storage capacity. However, with higher amounts of SMC (above 75%), the water-holding capacity drastically reduced; the medium was unsuitable for seedling growth [13]. Increased salinity and EC due to high levels of potassium, nitrogen, and phosphorus was associated with water-holding capacity. Growth deceleration of seedling germination was mostly due to phytotoxicity.

Few studies report poor development of tomato seedlings, when grown in SMC-supplemented medium without additional fertilizer; nutrient deficiencies inhibited their growth [68, 70, 71]. However, Meng et al. [69] revealed that SMC can completely replace peat as a growth media and does not require any chemical fertilizer, which presents an opposing situation. The growth parameters of the medium, such as seedling vigor, biomass, quantity of leaves, shoot height, and stem diameter, were significantly higher in this study.

In a different research, Meng et al., [69] used SMC medium for tomato seedlings. Waste reuse provided to be a beneficial aim, both for the environment and for the cultivated plants. Tomato output increased with the addition of SMC; total amount of tomatoes were the highest when 100% SMC medium was applied. Seedlings produced in substrates supplemented with SMC demonstrated higher vigor which results in higher yield on the field. SMC provided the necessary NPK to the tomato plants resulting in increased yields and quality.

The application of spent Agaricus subrufescens compost in the integrated production of seedlings and tomato plants has been studied as a technology, and it has been found that using Agaricus subrufescens SMC in different proportions improves tomato seedling quality and performance after transplanting [38]. Furthermore, the higher the proportion of SMC used, the higher the yield obtained. The study has also indicated that SMC serves as an environmentally friendly growing medium that contributes to waste reuse and enhances the productivity of tomato seedlings [72]. Moreover, tomato seedlings derived from A. bisporus and A. subrufescens exhibit diverse rhizospheres, containing beneficial species such as Chaetomium globosum and phytopathogens like Olpidium brassicae, along with numerous unclassified species or sequences [72].

Integration of SMC into lettuce production technology

Marques et al. [73] found that the quality of a commercial substrate improves significantly when 45% of A. subrufescens SMC is added; this mixture improved the quality, vigor, and yields of lettuce. Beyond 45% ratio, the substrate quality becomes to be deteriorative, most likely due to high EC and salinity in SMC. However, it is crucial to stress that, even for higher SMC (75%) content, more favorable seedling quality was reported, compared to the control (0% SMC). For plants grown in 48% SMC-supplemented medium, fresh head weight improved to a peak value of 233.45 g/plant. Fresh head weight of mature plants gradually decreased with the increase of SMC in the medium. Comparable outcomes for dry head material were reported, with a maximum of 18.1 g/plant for 45% SMC-aided medium. This ratio was considered by the authors as the ideal for maximizing seed vigor and biomass [73].

Liu et al. [74] investigated the growth and nutritional composition of lettuce seedlings as well as the impact of mixed seedling substrate mixtures [75]. The findings demonstrated that height and root length index increased with increasing SMC content; the number of leaves decreased, and their phosphorus and potassium content steadily increased at the same time. The 50% SMC-aided substrate performed the best in terms of root length, leaf number, shoot fresh and dry weight, and biomass. It was concluded that the addition of 50% SMC content was the most appropriate for lettuce seedlings development.

Agaricus subrufescens, Pleurotus spp., and Lentinula edodes SMC were also evaluated as promising medium components for growing lettuce plants [73, 76, 77]. Commercial peat was substituted with 66–78% SMC. The SMCs contained soluble salts, trace elements, and general mineral elements, such as NPK (1.3–4.2:0.1–0.4:0.5–1.8%), Mg (0.2–0.4%), and Na (0.05–0.2%). The A. subrufescens SMC was also used in the cultivation of cabbage and applied as a soil conditioner and an organic fertilizer [76]. The SMC used in this study improved the growth characteristics of lettuce by improving the overall growth and by soil bioremediation to eliminate the toxins in the soil. A similar research on organic vegetable fertilization using SMC reveals that SMC can increase lettuce and onion yields and is a suitable alternative to inorganic fertilizers [78]. SMC has a significant positive impact on lettuce output, growth, and compostability.

A novel technology was employed to assess the impact of the production environment on the cultivation of lettuce and arugula using SMC. Three distinct types of SMC were utilized, namely Agaricus subrufescens, Pleurotus ostreatus, and a combination of 50% Agaricus subrufescens and 50% Pleurotus ostreatus SMC, each applied at three different doses (1, 2, and 4 kg m−2). The findings revealed the feasibility of using fresh SMC to cultivate lettuce and arugula, with favorable outcomes observed in both field (F) and greenhouse (GR) conditions. In greenhouse pots, it was recommended to employ a combination of Agaricus subrufescens and Pleurotus ostreatus SMC at a dose of 4 kg m−2 [79]. Furthermore, an investigative study explored the utilization of compost derived from spent mushroom substrates of Agaricus bisporus and Pleurotus ostreatus as a component of growing media for cultivating baby leaf lettuce under the biotic stress induced by Pythium irregulare. The compost generated from these substrates can be reintroduced into production systems, potentially leading to increased yields of red baby leaf lettuce and suppressing activity against Pythium irregulare [34]. When compared to the outcomes of NPK treatments or no fertilization, the application of A. subrufescens and L. edodes SMC increased the soil microbial population and significantly increased the dry weight of lettuce plants [76].

Integration of SMC into pepper production technology

To produce pepper seedlings (Capsicum annuum L.), the most popular commercial growing medium is a blend of 70% peat and 30% perlite. However, compost made from SMC can also be used as a growing substrate and is capable of improving production in terms of growth, quality, and nutrient contents of pepper seedlings [80]. For the cultivation of pepper, Pleurotus spp. SMC was used [68]. Pot experiments with a variety of microorganisms and Pleurotus ostreatus were executed to examine the effects of microbial manures (microorganisms with the residue of mushroom medium) on pepper yield, nutrient absorption, and nutrient availability. Besides yield, changes in the alkaline hydrolysis-related N, P, and K components of the soil, as well as the overall N, P, and K contents were measured [68].

The results demonstrated that microbial-composted manure increased pepper output while enhancing soil fertility and the overall N, P, and K contents of the pepper plant. The combination of SMC, Bacillus megaterium, and Streptomyces sp. produced the best outcomes [81]. In addition, this study investigated the impact of composted Pleurotus ostreatus strain P-31 SMC on the development and productivity of pepper and tomato seedlings grown in a greenhouse. The different percentage amounts of sandy loam soil (0, 5, 10, 15, 20, 25, and 30) were created. Lower amounts (5–15%) of SMC promoted vegetative growth.

The growth and yield enhancements of tomato and pepper seedlings serve as examples in the study of the advantages of SMC as a soil amendment for the development of flowers, fruits, vegetables, and leaf crops [82]. The goal of the study was to establish a connection between the nitrate content and soil abiotic factors, endophytic organisms, and soil bacterial communities as well as to determine the effects of nitrification inhibitors in SMC, (dicyandiamide (DCD), and 3,4-dimethyl pyrazole phosphate (DMPP)) on the nitrogen levels of pepper fruit. The results showed that, in contrast to fruit, SMC interventions significantly changed the microbial population structures in soils and roots. Nitrate concentrations and the proportions of aerobic chemotypic heterotrophy function in fruit samples exhibited a strong and positive association [83].

Another research study on pepper fruits investigated the growth, quality, and nutrient traits in a SMC-supplemented growing medium. It was found that using a mixture of 70% aged SMC + 30% perlite is feasible in terms of germination ratio, stalk diameter, height, leaf number, macro element contents, fruit number, size, and quality [80]. SMC from oyster and button mushrooms can enhance the growth yield of Capsicum annuum L. and Solanum tuberosum L., promoting plant height, branch number, yield, and overall growth. SMC is believed to mobilize soil phosphate, while increasing root and leaf phosphate [84]. A recent study investigated the effects of SMC on pepper seedling growth, quality, and nutrient content, using fresh and aged, perlite, as well as mixed materials. The results revealed that a mixture of 70% aged SMC and 30% perlite, as well as the use of aged compost, was more effective in terms of germination ratio, stem diameter, height, leaf number, and macroelement contents [80].

Integration of SMC into cucumber production technology

The cultivation of cucumbers (Cucumis sativus L.) using the SMC was also tested, using Flammulina velutipes and Pleurotus SMC [13, 55]. It was found that it has favorable physical and chemical properties for nurseries; in case of tomato and cucumber seedlings, increasing plant height, leaf area, fresh weight, dry weight, and seedling quality index was experienced. The amended treatments with SMC showed better growth parameters compared to the control treatment without SMC. Additional studies are necessary on SMC as a peat replacement candidate for agricultural techniques [13]. A study was executed on the effects of using leached waste mushroom manure as a growing substrate component for horticultural plants including cucumber; plant growth rate based on fruit quantity and plant height was measured. The results showed that growing the cucumber plants with 15% and 25% leached SMC significantly improved their growth [85]. Studies on cucumber output, growth, and recycling have also demonstrated that SMC can improve all these traits. The positively impacted characteristics were overall yield, fruit width, fruit length, total soluble solids, yield of first-quality fruit, and nutrient content [13, 86].

Bioremediation, using living microorganisms like bacteria, fungi, or even plants, is the process of neutralizing or eliminating unwanted chemicals from air, soil, or water. SMC has been found to be somewhat helpful in reducing environmental contamination. Mushrooms are cultivated on suitable organic substrates. Spent mushroom compost from Agaricus bisporus has been used to grow cucumbers, lettuce, and other vegetable crops; some formulations even include cereal straws and seeds [2]. SMC has been shown to enhance plant growth while reducing the incidence of cucumber Fusarium wilt disease. This suppression is likely attributed to the manipulation of the soil microbial community in the rhizosphere, which includes reducing the population of Fusarium oxysporum f. sp. cucumerinum (FOC), stimulating beneficial microbes, increasing microbial activity, and altering microbial structure. These findings suggest a potentially cost-effective approach to controlling Fusarium wilt in cucumbers. However, further research is necessary to validate the suppressive effect of SMC amendments for practical application [55]. In addition, a study explored the utilization of SMC as a soil supplement and disease control method in cucumber plantations, resulting in an increase in germination rates from 35 to 92%. Nevertheless, SMC treatments had a negative impact on disease incidence, possibly due to the presence of antimicrobial substances [87].

Testing fresh or pasteurized F. velutipes SMC in cucumber cultivation produced a substantial increase in total organic carbon, dissolved organic carbon, and microbial biomass carbon, when compared to NPK-fertilized and unfertilized media [88]. When compared to soil treated with mineral fertilizer, the fresh SMC-amended soil had higher levels of microbial diversity and enzyme activity. Similarly, the addition of A. bisporus SMC to soils enhanced the co-occurrence of bacteria and fungus, and the relative abundance of microbial hubs had a favorable effect on plant yield [89].

Integration of SMC into eggplant production technology

Pleurotus SMC was used to support eggplant (Solanum melongena L) seedling growth. For eggplant and pepper seedlings, peat moss is mostly used. Imported peat can be substituted using SMC [90]. In addition, the effects of various media, such as cocopeat, split mushroom compost, perlite, volcanic basalt, and sawdust, on the quantity and quality of eggplant fruits ere investigated. Comparing these media to other commercial media, results demonstrate that all of them improved the quality of eggplant fruits [91].

A study investigated how SMC impacted the quality and nutritional content of eggplant seedlings grown under different conditions. The findings showed that the most favorable results were obtained when seedling mixtures with various nutrient levels were grown in peat with perlite. The greatest difference between the two different substrates was their seedling fertility and nutritional content (30% perlite and 70% SMC). It was discovered that discarded mushroom parts could be used as growing substrate for eggplant seedlings [92]. Spent mushroom compost could be used as a replacement medium to improve the vegetative growth, reproductive development, quantity, and quality of eggplant in open areas and in indoor settings. SMC is essential for maintaining and enhancing the nutrient content of substrates for eggplant and can be a practical substitute for synthetic fertilizers [93]. The findings presented in the research explore a range of technologies excluding SMC, as shown in Table 2.

Table 2 Studies on the different technologies for some vegetable production out of SMC
Full size table

Conclusion and future recommendations

SMC is appropriate for use in agriculture as a low-cost alternative growing medium for vegetable production or as a soil supplement to provide nutrients and restore soil fertility. SMC is a rich source of organic matter and a vital supply of micro- and macro-components for plants and food crops, enhancing soil microflora and biological activity in farmlands. Compared to peat, SMC had higher pH value, higher salt content, lower concentrations of macro- and micro-nutrients, and lower water-holding capacity, but much higher air capacity potential. The negative consequences of excessive peat mining in wetlands and peatlands may be lessened by substituting peat with SMC, since peat is a non-renewable natural resource. Therefore, it is important to optimize the entire production process and ensure that the composting and cultivation practices are consistent to achieve maximum efficiency in the reuse of SMC enzymes and other resources by turning them into economically viable agricultural resources. However, significant environmental impacts of SMC manufacturing and transportation may include greenhouse gas emissions, resource depletion, and the spread of infectious diseases. When using SMC, it is crucial to consider its disadvantages, threats, and limitations, as well as to ensure applications in the right amounts, avoid contamination, and protect the environment. In addition, implementing a circular economy approach in mushroom production can also create new opportunities for sustainable economic growth.

The present review focuses on the existing level of knowledge about agricultural applications of SMC, analyzes the possible challenges, and proposes future directions for the sustainable development of the global mushroom industry. The knowledge gaps of SMC use were identified as follows: (1) The practical applications of SMC in the cultivation agriculture and vegetables aiding disease management, that cause substantial crop losses by bringing soil-borne plant pathogens when compared to other biological control strategies. (2) SMC harbors vast numbers of beneficial microorganisms that can be effective in the control of crop diseases. Their mode of action is inducing microbiostasis, stimulating host systemic resistance as well as production of toxic substances against the pathogens affecting crop vegetables, specifically lettuce, pepper, cucumber, eggplant, and tomato. (3) SMC, a waste material, poses significant challenges for mushroom growers due to disposal, transportation, energy consumption, and environmental risks like greenhouse gas release and water contamination. (4) The EU Council Directive prohibits landfilling of SMC due to its bulky nature and high water content, posing environmental pollution and threatening mushroom industry growth. (5) SMC techniques are being explored to mitigate the detrimental effects of pesticides on human health, highlighting the need for sustainable agronomic practices.

Future research might benefit from the application of SMC as organic waste material and biological control of diseases to gradually replace the toxic chemical pesticides and fertilizers, which are today’s most widely and indiscriminately used method in agriculture. The use of SMC in vegetable cultivation will offer a more environmentally responsible alternative to chemicals as well as to peat. SMC and biomass utilization is a viable waste management strategy for a circular economy and sustainable agriculture.