Ichu Valorization by Pleurotus spp. Cultivation and Potential of the Residual Substrate as a Biofertilizer

1. Introduction

High-Andean grasslands, which cover 14.2% of Peru’s territory [1,2], are vital ecosystems of both economic and environmental significance. These regions support extensive livestock, primarily involving camelids, cattle, and sheep—an activity that constitutes a crucial income source for local communities. Additionally, these grasslands serve as the most cost-effective source of fodder, sustaining up to 84% of the country’s high-Andean livestock production [1]. Beyond their economic role, high-Andean grasslands provide essential ecosystem services, including carbon sequestration—estimated at 0.5 gigatonnes per hectare—and water regulation, which enhances soil infiltration and aquifer recharge during dry periods [3,4]. Furthermore, fodder vegetation coverage mitigates soil erosion in mountainous landscapes, while deep-rooted grasses contribute to soil structure stability and humidity retention [5]. These ecosystems also serve as habitats for endemic fauna and provide essential resources for farming communities, including construction materials and fuel for heating homes and cooking food (energy source) [1,6].

High-Andean grasslands provide essential economic and environmental benefits; however, 62% of these ecosystems are undergoing degradation [7] and face significant threats from traditional burning practices, overgrazing, and the impacts of climate change [8,9]. Among these threats, grassland burning—although a cost-effective and rapid method—results in biodiversity loss, soil fertility depletion, and exacerbation of climate change effects. This practice leads to a decline in bacteria and fungi essential for biogeochemical cycles, organic matter loss, and alterations in key soil properties, including pH and bulk density [10]. Given these challenges, adopting sustainable management strategies for high-Andean ecosystems is imperative.

One potential sustainable use of the Ichu (Jarava ichu) is as a substrate for cultivating edible mushrooms. J. ichu, a species of the Poaceae family, is characterized by its upright growth, forming dense tillers with stems reaching up to 180 cm in height. This grass thrives in high-Andean ecosystems from 3 000 above sea level (masl) [11] and is predominant in the grasslands of the jalca [12], puna, and paramo (Spanish term for high moorland) ecoregions. It is also distinguished by its easy availability, low harvesting cost (~0.15 USD∙kg^-1) [11], and high lignocellulose content [13]. As a native and wild-growing species, J. ichu does not require cultivation or compete with other crops for agricultural land use. Its annual production in Peru is approximately 76 kt [14]. These characteristics position the Ichu as a promising resource for various innovative local applications, including its potential use as a substrate for cultivating edible mushrooms, particularly the genus Pleurotus spp. This genus is widely recognized for its high nutritional value [15,16] and medicinal properties [17]. Additionally, Pleurotus species offer advantages such as rapid growth, minimal environmental requirements, heavy metal absorption capacity, and resistance to diseases and pests [18].

Mushroom cultivation not only provides direct benefits but also generates a valuable by-product: spent mushroom substrate (SMS) residue, which can be used as an organic amendment or biofertilizer to enhance soil fertility and quality [19,20,21]. Incorporating SMS as a soil amendment alters soil composition and porosity [22] while enriching its mineral profile [23]. SMS is characterized by a high content of extracellular lignocellulolytic enzymes, including ligninases, cellulases, hemicellulases, and pectinases. These enzymes degrade the polysaccharides in the residual substrate’s cell walls, breaking them into a wide range of organic compounds (such as carbohydrates, proteins, and lipids) and inorganic compounds, including ammonium nitrate [24]. This increased nutrient bioavailability facilitates the rapid propagation and colonization of fungal mycelium during mushroom production [25] and makes SMS a valuable resource for reuse. In this context, lignocellulosic SMS residues derived from Jarava ichu used as a substrate for Pleurotus cultivation, which would otherwise have no significant economic value, represent a promising resource for generating novel bio-inputs. These include biofertilizers for agriculture, reusable substrates for edible mushroom cultivation, and high-nutritional-value feed for livestock [23,25].

Although various lignocellulosic agricultural by-products have been evaluated as substrates for edible mushroom cultivation [26,27], the Ichu—despite its high lignocellulose content and wide availability—has not yet been studied for this purpose in Peru. Its utilization could mitigate the need for pasture burning and provide a novel source of functional foods, given its nutraceutical properties and bioactive compounds, which serve as natural sources of antioxidants, proteins, and amino acids [28]. Additionally, J. ichu holds potential for biofertilizer production, contributing to the sustainability of high-Andean agricultural systems. Therefore, this study aimed to evaluate the efficiency of the Ichu as a substrate for Pleurotus spp. cultivation and assess the residual substrate's potential as a biofertilizer, proposing a sustainable strategy for managing high-Andean ecosystems.

2. Materials and Methods

2.1. Literature Search and Dataset Construction

Ichu samples (6 Kg) were randomly collected from a 2 m × 2 m (4 m²) plot with homogeneous characteristics, including vegetation coverage, age, and height. Within this designated plot, stems were extracted exclusively from tillers in the senescence stage—a phenological phase characterized by the lowest humidity levels in the species' growth cycle. The sample collection site is situated at an altitude of 4 050 m. a. s. l., with geographical coordinates 418914.20 East and 8647138.14 North, in the district of Tomas, province of Yauyos, department of Lima, Peru.

The fungal species Pleurotus citrinopileatus, Pleurotus djamor, and Pleurotus ostreatus, known for their ability to degrade lignocellulosic materials, were used to assess the Ichu’s suitability as a potential substrate for its cultivation. These species were supplied by a company specializing in research, product development, and innovative solutions based on edible and medicinal mushrooms.

Raphanus sativus var. Crimson Giant was used to assess the use of spent mushroom substrate as a biofertilizer derived from the cultivation of Pleurotus species.

2.2. Proximal Analysis of the Ichu-Based Substrate

The Ichu samples were transported to the Food Analysis Laboratory of the Nutritional Research Institute (IIN) for proximal analysis and determination of their main components. Humidity, ash, fat, protein, and crude fiber contents were measured following AOAC (2023) standard procedures [29]. Carbohydrate content, total energy and kilocalorie values were calculated using the MS-INN method described by Collazos (1993) [30].

2.3. Cellulose and Lignin Analysis in the Ichu-Based Substrate

The cellulose and lignin analyses in the Ichu samples followed the official ANKOM reference methods [31] for their quantification: cellulose (ANKOM, 2005. Method N° 5) and lignin (ANKOM, 2005. Method N° 8). These analyses were performed at the Food Nutritional Evaluation Laboratory of the Universidad Nacional Agraria La Molina, Peru.

2.3. Pleurotus spp. Cultivation

The fungal cultivation process was conducted following the procedure described by Akcay et al. (2023) [32], with some modifications. Initially, Ichu was chopped into 3–4 cm fragments, and a total of 3 600 g was weighed and evenly distributed into nine perforated polypropylene bags, each containing 400 g. The sealed bags were then immersed in drinking water for 12 hours. To remove excess humidity, the bags were drained for one hour before transferring the material to new polypropylene bags for autoclaving at 121 °C for 15 minutes. After sterilization, the substrate was allowed to cool to room temperature. The fungal species P. citrinopileatus, P. djamor, and P. ostreatus were then inoculated separately using wheat seeds colonized by the mycelium of each species, following the modified method of Rodríguez et al. (2021) [33]. To prepare the mycelium-colonized seeds, 100 g of shelled wheat seeds were washed with detergent and rinsed thrice. The seeds were placed in 250 mL Erlenmeyer flasks and autoclaved at 121 °C for 15 minutes. Once cooled to room temperature, the seeds were inoculated with a 10 mm diameter agar disc containing mycelium previously grown on PDA agar. The inoculated seeds were incubated in the dark at 28 °C for five days until fully colonized by the mycelium. Contamination absence was assessed through visual inspection, and any samples exhibiting abnormal coloration or lacking mycelial growth were discarded. The wheat seed inoculum accounted for 8.1% of the dry weight of the substrate in each Pleurotus culture bag.

The experiment was conducted with three replicates for each Pleurotus species. Substrate-filled bags were maintained in an incubation chamber at 25 °C with 70–80% relative humidity for 21 days. Once mycelial growth became abundant and/or primordia had formed, the bags were transferred to the fruiting chamber for 7 to 10 days. At this stage, a 2 cm incision was made in two central areas on the lateral sides of each bag to facilitate the development of fruiting bodies or basidiocarps [34], as shown in Figure 1. Relative humidity and temperature in the incubation chamber were monitored using a Giardino HTC-2 digital thermo-hygrometer to ensure stable conditions within the recommended parameters.

2.4. Productivity Indicators of Pleurotus Cultivation

Mushroom productivity was assessed using the following indicators: the cultivation cycle (CC), biological efficiency (BE), and production rate (PR). The CC was defined as the number of days from sowing to the last harvest. The BE was calculated as the ratio between the mushroom's fresh weight (g) and the dry weight of the substrate (g), as stated by Salmones et al. (1997) [35]. The PR was determined as the quotient of BE and the total time elapsed from inoculation to the last harvest [36].

2.5. Proximal Analysis of Pleurotus

The proximal analysis of the fruiting bodies of P. citrinopileatus, P. djamor, and P. ostreatus was conducted following established procedures in official reference methods for the quantification of key parameters: protein (AOAC 2001.11.2023) [29], humidity (NTP-ISO 1442.2006) [37], ash (NTP 201.022.2002) [38], total fat content (NTP 201.016.2002) [39], and crude fiber (AOCS-BA 6-84.2017) [40]. Carbohydrate content was determined using the MS-INN method described by Collazos (1993) [30]. These analyses were performed at the Food Analysis Laboratory of the Nutritional Research Institute of Peru.

2.6. Potential of Pleurotus SMS Spent Substrate as Biofertilizer

The effect of the post-culture substrate from P. citrinopileatus, P. djamor, and P. ostreatus on the germination of Raphanus sativus var. Crimson Giant was evaluated. The experimental design included three treatments (T1, T2, and T3), in which 50 mL of spent substrate from P. citrinopileatus, P. djamor, and P. ostreatus were mixed with 450 mL of sterile soil. The control treatment (Tc) consisted of 500 mL of sterile soil, with fertilization provided by a hydroponic solution sourced by Universidad Nacional Agraria La Molina. This solution was prepared by diluting 0.5 mL of Solution A and 0.2 mL of Solution B in 100 mL of irrigation water. A completely randomized design was used, with each treatment replicated five times. In each replicate, two seeds of Raphanus sativus var. Crimson Giant were sown. The germination percentage was recorded for each treatment.

In addition, the chemical characteristics of the residual substrate from each of the three Pleurotus species were analyzed following official AOAC standard procedures [29,41]. The assessed parameters included humidity (AOAC 930.04, 2023), nitrogen (AOAC 2001.11, 2023), pH (AOAC 981.12, 2023), phosphorus (AOAC 970.39, 2019), and potassium (AOAC 975.03, 2019). All analyses were conducted at the Food Analysis Laboratory of the Nutritional Research Institute of Peru.

2.7. Economic Analysis or Valorization of Pleurotus spp. Cultivation on Ichu

The economic viability of cultivating Pleurotus spp. using J. ichu as a substrate was assessed through a methodological framework encompassing mushroom production, the residual substrate's valorization, and the production system's financial analysis. A 24 m² production area was established for a small-scale, resource-limited producer. The processing capacity was 150 kg of dried Ichu per production cycle. Fixed and variable costs were determined, considering infrastructure, inputs, labor, transportation, and energy. Fresh mushroom production was estimated at 490 kg annually, costing $3.56 per kilogram. A benchmark selling price of $6.58∙kg-1 was established, enabling the net profitability of the system‘s calculation. Additionally, the input-output ratio and rate of return on investment were estimated to evaluate the financial feasibility of the system.

2.8. Data Analysis

Treatment comparisons were conducted using analysis of variance (ANOVA) for a completely randomized design (CRD) with SPSS software (version 26) at a 95% confidence level. Significant differences between treatments were identified through multiple comparisons using the Tukey HSD test as a post hoc analysis. Additionally, ANOVA assumptions, including residual normality and homogeneity of variances, were assessed using the Kolmogorov-Smirnov and Levene tests to ensure the statistical validity of the results.

3. Results and Discussion

3.1. Proximal Composition of Ichu

The nutrient composition of the substrate directly influences the chemical composition and biological characteristics of Pleurotus spp. [42]; therefore, the proximal composition of Ichu was determined. The results indicated that crude fiber (38.90 g∙100 g-1) and carbohydrates (40.26 g∙100 g-1) were the primary components of this material (Table 1). The protein content (5.53 g∙100 g-1) was also recorded, which falls within the range reported for J. ichu (3.43–7.17%) across different seasons, as described by Mamani-Linares and Cayo-Rojas (2021) [43]. Furthermore, the humidity content of the analyzed samples at the senescence phenological stage aligned with the values reported by Mori et al. (2019) [14]. During this stage, the species undergoes loss of green pigmentation, wilting of plant structures, and the plant's progressive drying, explaining the reduction in humidity levels compared to other phenological stages. For instance, in previous stages, humidity values as high as 57% on a dry basis have been observed [44].

Regarding energy content, the majority of the available energy in Ichu is derived from carbohydrates (161 kcal∙100 g-1), followed by protein (22 kcal∙100 g-1) and fat (6 kcal∙100 g-1). This composition profile makes Ichu a suitable substrate for mushroom mycelium growth, providing an optimal energy balance and essential nutrients.

In mushroom cultivation, the nitrogen content of the substrate plays a crucial role in mycelial development, as it is essential for cell wall formation, as well as protein, nucleic acid, and polysaccharide synthesis. Furthermore, nitrogen directly influences the growth and yield of Pleurotus spp. [42]. For instance, Rizki and Tamai (2011) reported that a substrate composed of oil palm residues with a nitrogen content of 2.09% facilitated complete mycelial colonization and enhanced the formation of initial structures (pinheads) in P. ostreatus [45]. However, excessive nitrogen can inhibit mycelial growth and slow its development (slower spawn run), as Baysal et al. (2003) observed [46]. Previous studies suggest that an optimal nitrogen range of 0.5%–1.5% in the substrate enhances the biological efficiency of Pleurotus spp. cultivation [47]. In this study, Ichu exhibited a nitrogen content of 0.88%, indicating that it falls within the optimal range for efficient Pleurotus spp. cultivation.

3.2. Cellulose and Lignin Content of Ichu

The cellulose and lignin contents in Ichu (J. ichu) were found to be 34% and 9.58%, respectively. These values are comparable and close to those reported for other species within the Jarava genus (synonymous with Stipa), such as Stipa obtusa, which has been documented to contain 38.07% cellulose and 15.56% lignin [14]. Variations in these values may be attributed to intraspecific differences, variations in environmental conditions, or the phenological stage of the plants at the time of sampling. According to Albarracín et al. (2019), the chemical composition of grasses undergoes significant changes throughout their life cycle, with cellulose and lignin concentrations progressively increasing as the species’s senescence advances [48]. Additionally, studies have demonstrated that factors such as altitude and soil type can influence lignin content in Jarava species and other seasonal grasses [43].

3.3. Productivity Indicators of Pleurotus Cultivation

The productivity of three Pleurotus species cultivated using Ichu as a substrate was evaluated using the following indicators: cultivation cycle (CC), biological efficiency (BE), and production rate (PR), as shown in Table 2. ANOVA results for each productivity indicator yielded a p-value > 0.05, indicating no significant differences in CC, BE, or PR among the three Pleurotus species grown on Ichu as a substrate. These findings suggest that, despite species differences, their yields were similar. Consequently, the average BE of the three species, 19.8%, will be used for further analysis. This BE value is higher than that reported by Puliga et al. (2022), who found BE values of 0.8%, 11%, and 10.8% for G. lucidum, L. edodes, and P. cornucopiae, respectively, using hazelnut husks as a substrate [49]. However, the 19.8% BE observed in this study is lower than the values reported in other studies. Nieto-Juárez (2021) reported a BE of approximately 60% using coffee husk residue as a substrate [27]. Obadai et al. (2003) found a BE of 50.64% for P. ostreatus cultivated on a rice straw-based substrate [50].

The differences observed in BE could be attributed to variations in the lignin content of the substrates. According to Albarracín et al. (2015), Ichu contains 45.9% cellulose and 18.2% lignin [44]. Similarly, Sims et al. (2008) reported that cellulose constitutes 40–50% of the dry weight of plant material, while lignin accounts for 15–20% [51]. In contrast, hazelnut husks have a lignin content of 40–50% (Puliga et al., 2022) [49]. These findings suggest that a high lignin content in substrates negatively affects fungal BE. Badu et al. (2011) emphasize the importance of substrate composition, particularly lignin content, in the cultivation performance of P. Ostreatus [52]. Lignin acts as a protective barrier, limiting cellulose and hemicellulose degradation and thereby reducing sugar availability for fungal metabolism. Additionally, it is essential to acknowledge that BE is influenced by multiple factors, including fungal species, substrate composition, and environmental conditions [53,54].

This study explores the potential use of Ichu as a substrate for mushroom cultivation. The results demonstrate that all three tested species successfully grew on this substrate, which has not previously been utilized for Pleurotus cultivation. Furthermore, the findings suggest that Ichu is as effective as other lignocellulosic substrates in supporting Pleurotus production. However, it is important to note that biological efficiencies above 50% are generally considered economically viable for mushroom cultivation, according to Ríos et al. 2010 [55]. Therefore, to optimize mushroom production, it is necessary to enhance the Ichu-based substrate by supplementing it with alternative substrates rich in easily metabolized carbohydrate sources to facilitate lignin degradation.

3.4. Proximal Composition of Pleurotus spp.

Mushrooms of the Pleurotus genus are widely recognized for their high nutritional value and beneficial medicinal properties [56,57,58], which according to previous studies, are influenced by cultivation conditions [59]. Table 3 presents the proximal analysis results for the main components of P. citrinopileatus, P. djamor, and P. ostreatus cultivated on Ichu substrate. The data indicate that humidity is the predominant component in all three species, ranging from 82.29% to 84.03%, followed by carbohydrates, which vary between 49.9% and 56.1%. Protein content was determined using a conversion factor of 4.38, a recommended value for fungi due to their high levels of non-protein nitrogenous compounds such as chitin [60,61]. Accordingly, protein content ranged from 24.1% to 30.41%. Fiber, ash, and fat were present in lower proportions, with values ranging from 1.50% to 13.59%. These results fall within the ranges reported in previous studies for Pleurotus species cultivated on various types of substrates [27,62,63,64,65,66,67]. Moreover, no significant differences (p > 0.05) were observed among the three Pleurotus species cultivated on Ichu substrate.

The humidity content observed in this study for P. citrinopileatus (82.69%), P. djamor (84.03%), and P. ostreatus (82.29%) falls within the range reported for P. eryngii (80.7%) (Ryu et al., 2015) [62] and P. ostreatus (88.2%) [27,64]. High humidity content is a common characteristic of edible mushrooms, making them highly susceptible to microbial growth and enzymatic activity, negatively impacting their shelf life and texture [64,68]. However, various preservation techniques for Pleurotus mushrooms have been reported for commercial applications [69,70,71].

The carbohydrate content on a dry basis in P. citrinopileatus (49.97%), P. djamor (50.59%), and P. ostreatus (56.18%) is comparable to values reported for Pleurotus spp, cultivated on substrates derived from various agricultural waste sources [65,66,72]. In mushrooms, carbohydrates—including monosaccharides and polysaccharides—serve as an energy source and are stored primarily as glycogen rather than starch, as in plants. Additionally, carbohydrates contribute to the characteristic taste of mushrooms (Kalač, 2016) [68].

The values of protein content in this study for P. citrinopileatus (30.41 %), P. djamor (26.18 %) and P. ostreatus (24.1 %), are higher or similar to those reported by previous studies for different Pleurotus species. In particular for P. ostreatus, P. sajor-caju, P. columbinus, P. sapidus; whose values ranged from 16.07 to 25.15 % [67]. The values of P. ostreatus cultivated on sawdust substrate and different organic fertilizers were between 19.27% and 33.41% [73]. Also, P. ostreatus and P. djamor reported values ranging from 17% to 35% and from 14.02% to 19.68%, respectively, using agricultural wastes (barley stubble and maize husk) as substrate [74]. Compared to the values obtained in this study, these are lower for P. djamar and P. citronopileatus, while for P. ostreatus they are within the reported range, although below the maximum value of 35%.

Silva et al. (2020) reported crude protein values ranging from 22.4% to 27.5% in P. ostreatus cultivated on agro-industrial residues from oil palm fruits and cocoa almonds as a substrate [66]. Additionally, previous studies indicate that nitrogen content in the substrate enhances protein accumulation in the fungus [65,66,75]. However, it must be considered that nitrogen concentrations equal to 1.5% or higher inhibit fungal growth [76]. Based on the present study's findings, Ichu is a suitable substrate for cultivating Pleurotus species with high protein content, enhancing their nutritional value.

The fiber content observed in this study was 10.57% for P. citrinopileatus and 10.7% for P. ostreatus, while P. djamor exhibited a higher value of 13.59%. These results exceed those reported by Peter et al. (2019), who found fiber levels ranging from 8.2% to 9.1% in P. ostreatus cultivated on agricultural residues such as cassava peels, banana leaves, and sawdust [77]. However, the obtained values in our study are lower than those reported for P. citrinopileatus (16.20%–21.6%) and P. ostreatus (13.0%–19.89%) grown on agro-industrial and forest residues [78,79]. Overall, mushrooms are an important source of dietary fiber, which, although indigestible by the human digestive system, provides numerous nutritional and physiological benefits [71].

Edible mushrooms have low lipid content (less than 5%), primarily composed of unsaturated fatty acids, contributing to their characteristic aroma [80,81]. In this study, the fat content determined for P. citrinopileatus (1.85%), P. djamor (1.50%), and P. ostreatus (3.9%) falls within this range. The obtained values for P. citrinopileatus and P. djamor are lower than those reported by İnci et al. (2023) [72], who found levels ranging from 2.0% to 2.3% using wheat straw and quinoa stalks as substrates. For P. ostreatus, the obtained fat content in this study (3.9%) is consistent with previously reported values, which range from 1.64% to 4.62% [75,77]. These differences underscore the lipid content variability depending on the fungal species and the substrate used.

The findings of this study indicate that the Ichu-based substrate is effective for cultivating Pleurotus spp., with notable protein, fiber, and carbohydrate content compared to previous studies. The three analyzed species exhibited superior nutritional profiles, particularly the protein content of P. citrinopileatus (43.39%) and P. djamor (37.35%), suggesting that Ichu could be a viable substrate source for producing mushrooms with high nutritional value.

3.5. Potential of Spent Mushroom Substrate as a Biofertilizer

Table 4 presents the chemical composition of the spent mushroom substrate (SMS) obtained from cultivating three Pleurotus species—P. ostreatus, P. citrinopileatus, P. djamor, and the Ichu substrate without mycelium. These results indicate that SMS is rich in essential nutrients such as phosphorus, potassium, and nitrogen, supporting its potential use as a biofertilizer. These findings align with previous studies highlighting the agronomic value of SMS [82,83]. Specifically, the humidity content of SMS ranged from 45.80 to 51.04 g∙100 g^-1, indicating a high water retention capacity, which is beneficial for soil hydration. This is consistent with the findings of Lipiec et al. (2021) [84], who demonstrated that SMS application increases field water retention capacity (at -100 h∙Pa) within a range of 42.4% to 48.5% at depths of 0–40 cm. Nitrogen levels in SMS ranged from 0.47 to 0.59 g∙100 g^-1, with P. ostreatus exhibiting the highest value. However, these nitrogen levels were lower than those found in Ichu without mycelium (4.02 g∙100 g^-1). Additionally, phosphorus content was significantly high in SMS, particularly in P. djamor (1296.9 ppm), followed by P. citrinopileatus (989.4 ppm) and P. ostreatus (795.9 ppm). These values were considerably higher than Ichu's (0.11 ppm), underscoring SMS as a rich source of this essential nutrient. Potassium levels in SMS ranged from 253.1 to 291.3 ppm, with P. citrinopileatus exhibiting the highest concentration. These values were substantially higher than those found in Ichu without mycelium (7.77 ppm). Similarly, Uzun (2004) reported that SMS is a good source of potassium and phosphorus but is relatively low in nitrogen [85]. However, when applied as a fertilizer, its nutrients are released gradually over an extended period, allowing for more efficient plant uptake. Furthermore, its use provides additional benefits, such as improving the soil's physical, chemical, and biological properties. Additionally, the pH of SMS ranged from 5.2 to 5.6, indicating a slightly acidic nature, which is optimal for nutrient availability in most agricultural soils.

The spent mushroom substrate (SMS) effect on seed germination was evaluated using SMS derived from P. citrinopileatus, P. djamor, and P. ostreatus alongside a chemical fertilizer control (Table 5). Germination rates were measured to assess SMS's biofertilizer potential. Treatment T1, which utilized SMS from P. citrinopileatus, achieved a germination rate of 90%, indicating its effectiveness in promoting seed germination. Treatment T2, incorporating SMS from P. djamor, recorded the highest germination rate (100%), likely due to its elevated phosphorus (1296.9 ppm) and potassium (262.6 ppm) content. Treatment T3, using SMS from P. ostreatus, resulted in an 80% germination rate, demonstrating its efficacy, albeit to a lesser extent than the other SMS treatments. Treatment T4, the chemical fertilizer control, also achieved a 90% germination rate, comparable to T1, suggesting that SMS from P. citrinopileatus and P. djamor can be as effective as conventional fertilizers. These findings align with previous studies indicating that SMS can enhance the nutrient content of the germination substrate by supplying essential elements such as nitrogen, phosphorus, and potassium, which are crucial for seedling development [86,87].

3.6. Economic Analysis of Pleurotus spp. Production

The cultivation of Pleurotus spp. using Ichu as a substrate presents a profitable alternative within edible mushroom production systems. To evaluate its economic viability on an artisanal scale, a processing capacity of 150 kg of Ichu was established within a 24 m² area, designed for management by an artisanal producer with limited resources.

The annual production cost is estimated at $1746.32. With a projected yield of 490 kg of fresh mushrooms per year, the production cost is $3.56 per kilogram. Given a selling price of $6.58∙kg-1, the net profit per kilogram is $3.02.

These values indicate a profitability of 84.6%, demonstrating that cultivation of Pleurotus spp. using Ichu as a substrate is viable and competitive, even on a small scale.

In addition to mushroom production, the residual substrate can be reused as a biofertilizer, adding further value to the production system, which consists of four key components: facilities, energy, transport, and labor [87]. In this study, SMS derived from Ichu demonstrated a superior input-output ratio compared to traditional organic fertilizers and has the potential to generate additional income by being sold as a soil conditioner, particularly for phosphorus- and potassium-rich soils [88,89,90,91].

In the future, recycling SMS as a fertilizer presents a valuable opportunity for its application in family farming, enabling production cost reductions through improved substrate management and enhanced crop yields. To maximize these benefits, optimizing the Pleurotus cultivation production process is recommended. Commercializing the residual substrate as a biofertilizer would also support investment recovery and enhance the system’s sustainability. Finally, expanding the market for edible mushrooms in high Andean communities is suggested as a viable alternative source of plant-based protein.

The use of J. ichu as a substrate for Pleurotus spp. in artisanal systems is not only profitable but also capitalizes on an underutilized resource, reduces environmental pollution, and provides a sustainable alternative to grassland burning. Furthermore, the residual substrate's potential as a biofertilizer enhances the system's economic and environmental viability, fostering more efficient and sustainable agricultural production.

5. Conclusions

This study demonstrates the feasibility of using J. ichu, a largely underutilized Andean resource, as a substrate for cultivating Pleurotus spp. and its subsequent application as a biofertilizer. The research presents an innovative production model that enhances sustainability and contributes to the valorization of Ichu in the high Andean regions of Peru.

J. ichu possesses a nutritional composition well-suited for cultivating Pleurotus spp. It has high levels of crude fiber (38.90 g∙100 g^-1), carbohydrates (40.26 g∙100 g^-1), and nitrogen (0.88%), which support mycelial development and enhance the fungus's biological efficiency.

Due to its high phosphorus and potassium content, the residual substrate from mushroom cultivation exhibits strong potential as a biofertilizer. This dual-use approach maximizes the utilization of Ichu, offering both a nutritious, protein-rich food source and a valuable agricultural input.

The findings of this study extend beyond the specific case of Ichu, highlighting the potential of other underutilized lignocellulosic resources in fragile ecosystems for similar applications. This approach could be replicated in other regions to enhance sustainability, reduce grassland burning, and mitigate environmental degradation.

This research proposes an integrated model that combines edible mushroom production with biofertilizer generation. This model provides a sustainable solution for the valorization of Ichu, supports agricultural development, and enhances food security in high Andean communities.

Further research is needed to optimize the cultivation process and assess the long-term impact of the residual substrate on different soil types and crops. Additionally, evaluating the economic feasibility of the model at a community scale and its social acceptance in high Andean communities would provide valuable insights for its broader implementation.

Researchers, policymakers, and local communities are encouraged to consider this production model as a sustainable strategy for valorizing underutilized natural resources and addressing environmental, social, and economic challenges in the high Andean regions of Peru and beyond.