Introduction

The emerging economies like India have intensely accelerated the mining activities, and with increased mining activities, land degradation is also exponentially increasing (Haigh et al., 2015; Li, 2018). As of today, the available landmass to mankind has reduced to 30% of total global land area and even less than 2–3% for India carrying 16% of global human population (Sahu & Dash, 2011). Mineral resources form the basis for production and manufacturing of products of industrial or commercial interests and strengthen the economy of a country; however, the mineral resource exploitation significantly impacts the ecology of the plant, soil fertility, and the environment (Xiao et al., 2020). For instance, coal mining in India is a major source of income as it is a major energy source enhancing the local economy. However, excavation of coal from deep soil damages the land, vegetation, biodiversity, and environment by changing the land cover disrupting the native ecological balance (Awotwi et al., 2018) and promoting soil contamination and ground water leaching of the toxic pollutants such as heavy metals (Sahu & Dash, 2011). Ecofriendly strategies are needed to be employed promoting research and technological intervention to monitor land degradation and suggest proper reclamation methods. Conventional management practices such as rehabilitation, reclamation, and restoration strategies using phytoremediation approach have significantly impacted the soil fertility and productivity and the associated microorganism populations and their activity (Diacono & Montemurro, 2010; Lal, 2008) in an exponential way thereby promoting soil microbiota safety and strengthening, soil fertility enhancement and productivity in the long term, and maintaining a continuous supply of nutrients cycled and fixed by soil biota (Hossain et al., 2017; Srivastava & Singh, 2017). Since soil biota have a key role in carbon cycling, organic matter decomposition, and maintenance of the seraphic fertility, preservation of soil microbial diversity is vital and essential. Soil microbial biomasses are the best indicators of soil health and are most sensitive to management practices which promote fundamental functioning (such as nutrient cycling and organic matter mineralization) both for soil and plants; therefore, any change in microbial biomass is directly linked to changes in soil physical and chemical properties which may indicate the need for improvement (Araújo & Melo, 2010). In this respect, various community-level physiological profiles (CLPPs) have been used to identify different microbial consortia in different habitats based on microbial carbon substrate oxidization mechanism which may further benefit the soil management (Muñiz et al., 2014).

Organic matter in soil is a potential reservoir for carbon sequestration and storage (CSS); in fact, it contains about twice as much carbon as in the atmosphere and highly relies on the management practices (Paustian et al., 2020). Land applications of organic waste provide substantial strategy to restore or rehabilitate the degraded lands having deteriorated productivity due to different developmental activities such as metal, ore, and other extraction activities. The urban areas are often associated with high municipal waste generation, for instance, about 1.3 billion tons/year (1.2 kg per capita/day) of waste is generated worldwide, and it is estimated to go beyond 2.2 billion tons/year (i.e., 1.42 kg of municipal waste per capita/day (Hossain et al., 2017). Out of this, more than 50% is organic fraction (Joshi & Ahmed, 2016; ISWA, 2020). The use of organic amendments or the organic waste is an alternative practice in agricultural sector, as they provide good nutrient sources and improves soil condition and productivity. Not only this, the amendments also modified the microbial biodiversity and activity, simultaneously minimizing the waste management problems (Chatterjee et al., 2017; Hossain et al., 2017; Padmavathiamma et al., 2008). Sustainable treatment of organic waste ensures significant nutrient accumulation within the organic residues. Black Soldier fly technology is one such waste treatment technology which has emerged as one of the most efficient technologies for composting and has significant potentials to replace commercial fertilizers (or organic soil amendments) (Singh & Kumari, 2019; Klammsteiner et al., 2020; Singh et al., 2021). The composting is mainly performed at the larval stage of the fly, and therefore, the treatment residues obtained after BSF larvae composting can be readily utilized as soil organic amendments since it has optimum nutrient status suitable to enhance soil productivity and plant growth (Klammsteiner et al., 2020).

Blended organic residues to create topsoil, for example, biochar and brown coal waste, have also been applied on mine tailings and other degraded soils in order to restore the land with its primitive ecological structures and functions by promoting the development of huge vegetation cover. Such strategies act as suitable options replacing the current accepted/applied technologies (Amoah-Antwi et al., 2020; Turan, 2021). Other organic residues such as woody biomass, straw, plant residues, farm yard manure, and sludge can also be used as soil conditioners which enhance soil properties like water holding capacity, bulk density, soil structure, microbial biomass, and enzymatic activity and mitigate pollutant bioavailability and greenhouse gas (GHG) emissions (Adekiya et al., 2019; Amoah-Antwi et al., 2020; Onagwu, 2019; Ren et al., 2019; Turan, 2021). Sugarcane industrial by-products used in a study showed improved productivity of sugarcane and soil health (Dotaniya et al., 2016). Previous studies, for instance, the study of Kumar et al. (2008) and Juwarkar et al. (2008, 2009), utilized organic amendments (such as ETP sludge and bio sludge from oil industry) with microbial inoculation in mine spoil dumps and successfully achieved the objective of fertile land restoration with dense vegetation and microbial population. Apart from these, cattle manure application has also been explored to study their effect on soil productivity. In one such study, cattle and poultry manure were used as soil amendments to determine the effects on different soil properties and plant growth such as phosphorus content. It was found that the phosphorus content was significantly increased in soil and root and shoot parts of the crop (Triticum durum) (Sonmez et al., 2016). Interestingly, the substantial use of plant-derived essential oil along with rhizobia also works as an effective soil activity enhancer since they provide pathogenic resistance without affecting the root nodulation and development of the plant (Turan et al., 2019). Despite the potential benefits, the technology is often accompanied with some risks associated with its application such as pathogen invasion, heavy metal contamination, and organic pollution (Dianco & Montemurro, 2010; Chen et al., 2018; Horta et al., 2018). The biological stabilization is a successful way to reduce the negative effects of the unstable organic matter in the soil and organic wastes (Rastogi et al., 2020).

The aim of the present work was to assess the response of organic waste amendments on the restoration of physicochemical and biological productivity on degraded lands. In this approach, waste products from industries were utilized as an organic amendment along with stress-tolerant nitrogen-fixing bacteria and fungi.

Materials and methods

Study site

Field study was carried out on an overburden dump of a coal and manganese mine site at Padmapur in Chandrapur and Gumgaon in Nagpur district of Maharashtra, India, respectively (Fig. 1). The area receives annual precipitation of 600 to 1000 mm and lies in a hot semi-arid region of India. The area has long hot summers, low humid conditions (during summers), and mild short winters. The soil type is characterized by ustic soil and has isothermal regime.

Fig. 1
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Details of site selected of reclamation in Gumgaon (Nagpur) and Chandrapur districts of Maharashtra

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Initial characterization of mine spoil, soil, and ETP sludge

Paper machine sludge (or ETP sludge) and press mud were collected from paper mill and sugar mill effluent treatment plant (ETP), respectively (Fig. 2), whereas soil was withdrawn from agricultural fields in close proximity of mine spoil representing the control conditions. Each sample (mine spoil, soil, ETP sludge, and press mud) was initially tested for physicochemical attributes, nutrient status, and microbiological properties. The chemical characteristics such as pH and electrical conductivity (EC) were determined according to the methodology, IS: 3025 (Part II) (1983). Soil organic carbon (%) was determined according to Walkley and Black method (1965). Macro and micro soil nutrients were analyzed as per standard methods (Jackson, 1958; Lindsay & Norvell, 1978). Microbial analysis was done as per standard procedure (1965).

Fig. 2
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Ameliorative materials (ETP sludge from paper and sugar mills) used for reclamation of mine spoil dumps

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Isolation and identification of biofertilizers strains

Soil samples collected from the neighboring areas of Tadoba Tiger Reserve were used to isolate the biofertilizer strains (Fig. 3) using the methodology of Ruangpan and Tendencia (2004) and Sanders (2012) with suitable modifications which were later inoculated in the rhizospheric region of different plant saplings (Gmelina arborea, Acacia auriculiformis, Tectona grandis, Phyllanthus emblica, and Delbergia sissoo) for acclimitization. The identified strains were Rhizobium, Azotobacter, and fungal species (Glomus and Gigaspora sp.).

Fig. 3
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Biofertilizer strains and Mycorhizzae isolated and inoculated for root development

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Field trial

Field trials were done at the coal and manganese mine site. Based on the previous pot study of Juwarkar et al. (2010), the treatment having the combination of four parts mine spoils, one part soil, and 100 t/ha ETP sludge and press mud (50:50) along with biofertilizers showed better results in terms of restoration of mine spoil dumpsite and higher survival rate of plants and therefore was selected in the current study. Plants were transplanted according to the standard Pitting technique of FAO (1978). Selected pit dimensions were 0.6 × 0.6 × 0.6 m encompassing the layer of organic bedding material having soil, sludge/press mud, and biofertilizers. In addition to this, 25 g vesicular arbuscular mycorrhizae (VAM) inoculum was also added.

Data analysis

The graphs were made using MS Excel 2016. One-way ANOVA followed by Tukey’s HSD test was used to determine the significant differences between different parameters of soil with respect to physical and chemical parameters and the nutrient status for both manganese and coal mine spoil for the duration of 25 years (Tables 1 and 2). The graphical values were calculated as mean.

Table 1 Physicochemical and biological parameters of mine spoil, top soil, press mud and restored manganese spoil
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Table 2 Physicochemical and biological parameters of mine spoil, top soil, press mud, and restored coal spoil
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Results and discussion

Effect of amelioration on rhizospheric development

Newly developed microbial population as a result of organic based amendments at the degraded lands stabilizes the soil structure, nutrient production, and plant growth by adopting a number of biochemical cycles (Oliveira et al., 2020). Similarly, in the present study, application of sludge and VAM (Glomus and Gigaspora) along with Rhizobium bio culture enhanced the development of root as well as nodule formation in leguminous trees as they act symbiotically which was very well evident from the high survival rate of the plants (Fig. 4). Uzarowicz and Skiba (2011) also showed enhanced rate of soil formation and functional root zone development due to bio waste amendments for sustainable plant community development. Reclamation of mine spoil dump depends upon the diverse increase in the soil microorganism due to application of biofertilizers. Maintaining high population of microbial diversity in the mine spoil helps in the restoration of nutrient content in soil and support enhanced plant growth. In addition to this, many growth-promoting substrates are generated during the various biochemical processes which help in promotion of growth and development of other microflora (Gopalakrishnan et al., 2015).

Fig. 4
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Enhancement of root development using biofertilizer (Mycorhizzae)

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Effect of amelioration on plant growth

Five plants (P. emblica, D. sisso, T. grandis G. arborea, and A. auriculoformis) were selected and assessed for various growth rate parameters in order to check the influence of ETP sludge and press mud and biofertilizers applied on coal mine spoil. Application of ETP sludge (100t/ha) and biofertilizers showed maximum growth, survival rate, and biomass productivity than the plant species planted without these ameliorations. This was due to the availability of nutrients in the mine spoil due to addition of endomycorrhizae biofertilizer. In addition to this, application of the ETP sludge to the mine along with microorganism modified the nutrient availability which was readily available for rhizospheric growth promoting fast plant growth development.

Earlier studies of Zornoza et al. (2012), Santibanez et al. (2012), and Rodriguez-Vila et al. (2014) have also shown predominant plant cover and richness along with improved soil chemical and biological parameters on the mine spoils of ferrousoxyhydroxides, sulfates, and heavy metals. However, maintaining organic waste amendments at field capacity is a major skill to prevent plant growth inhibition by accumulation of higher salt concentrations or other pollutants (Wijesekara et al., 2016).

Effect of amelioration and use of mycorhizzae/biofertilizers on plant survival

The survival rate of different plants transplanted on manganese and coal mine spoil amended with organic waste is given in Table 3. It is to be noted that the survival rate was slightly higher for manganese spoil as compared to coal mine spoil. Controls showed only 18% of the survival which may be due to very low nutrient availability in the mine spoil. However, the amendment with ETP sludge, press mud, and biofertilizers increased the survival rate above 90% for both coal and manganese spoil for different species by providing additional nutrients to plants and restoring the optimum functioning capacity of soil. The significant development and expansion of rhizosphere due to biofertilizer inoculation strengthened the microbial biodiversity and their functioning; as a result, the plants showed high survival at the amended mine spoil. In addition, the amendment with organic waste and biofertilizers also enabled the stress tolerance capacity by establishing nutrient balance. Apart from this, significant increase in the plant height was also observed as follows: Acacia auriculiformis, Gmelina arborea, Phyllanthus emblica followed by Tectona grandis and Dalbergia sisso respectively (Fig. 7A and B). Significant difference among the plant heights was found for the entire period of the experiment (0, 10, 15, and 25 years) for both manganese and coal mine spoils (p < 0.05). In case of growth pattern of different plant species also, no significant difference was found at initial stages (p value = 0.48). However, after 10-, 15-, and 25-years, significant difference was found among all plant species at p value = 0.00. Similarly, significant difference among heights of different plants species was also found at manganese spoil at p value = 0.00 (alpha value = 0.05) using Tukey’s HSD test. Rich and productive growth of selected plant species along with other vegetation was encountered post 3 years of plantation, forming huge biodiversity and restoring the biological productivity on coal mine spoil dump. Adding weightage to this study, Corrêa et al. (2018) also concluded that the amendments with sewage sludge achieved the fastest and the highest development of vegetation cover and the re-vegetation of exploited mine lands in a due course of time. The NPK status and organic content of mine spoil were lesser at the initial stages. Therefore, addition of ETP sludge and press mud supplemented the spoil with high organic matter which fulfilled the required organic content as well as nutrients for the microbial growth and plant growth (Tables 1 and 2). Many studies have been reported regarding the increase in the nutrient status as well as organic content by application of press mud as amendment, thereby enhancing plant growth as well as soil fertility (Gupta & Kumar, 2000; Tripathi et al., 2004). Due to the high content of sugar in the press mud, it also promotes high microorganism growth. In addition to this, the top soil was applied, which is used for the filling of pits at initial stages. The bulk density and water holding capacity of the used soil was 1.25 ± 0.02 g cm−3 and 56.40 ± 2.5%, respectively. Topsoil enhanced plant growth at the earlier stages of stabilization of plants. The reduced concentration of manganese (Mn) was observed during the course of time. The trend for decrease in Mn content for different period of years is shown in Table 1. Availability of manganese is reduced by addition of the amendments by immobilization processes thereby reducing the toxicity. Similar studies were conducted in order to determine the mechanism of Mn reduction by adding amendments such as press mud. In addition to this, pot studies conducted by Juwarkar et al. (1992) also determined the role of amendments containing high organic content for the reduction of the Mn as well as minimizing toxicity to the native plants and observed the positive correlations. Also, according to Brown et al. (2014), there is no transmittance of the pollutants to the mine spoil due to the application of organic amendments, bio solids, and lime solution. Similarly, immobilization of cadmium in soil is reported by Lee et al. (2013) and Defoe et al. (2014). On considering all these facts and the scenarios, it may be concluded that plantation is the best available option for the restoration/rehabilitation of mine spoil site. Based upon the field scale results, the survival rates of the plants at mine spoil site are given in Table 3 which showed that T. grandis (Teak), D. sissoo, A. indica (Neem), and P. pinnata (Pongam oiltree) have 95% and above survival rates.

Table 3 Effect of sludge- and biofertilizer-based ameliorated land on survival of plants on coal and manganese spoil
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Effect of amelioration on biological productivity and microbial biomass

Microbial community showed to be increased gradually at the mine spoil site at Gumgaon. Similarly, studies of Mingorance et al. (2014) and Jones et al. (2012) also indicated increased microbial biomass carbon (MBC) and the enzymatic activity of microbes at the amended sites. Jones et al. (2011) and Mora et al. (2006) in their study showed increased MBC from 0.0 to 55.0 mg C kg−1 and 19.6 to 164.9 mg biomass C kg−1. Similarly, studies of Ok et al. (2011) and Choi et al. (2014) showed increased SOM (soil organic matter), nutrient availability, and microbial populations in soil using bio wastes.

In the present study, after a span of 10 years, thick tree canopy was developed at the mine site which favored the immigration of animals showing increased biodiversity of animals and vectors and pollinators. As a result, transmittance or seed dispersal mechanisms occurred, and therefore, an established ecological community was formed at the respective mine site. Similar results in terms of substantial development of vegetation at amended land were reported by Brown et al. (2014). However, Taheri and Bever (2011) showed lower survival rates of the plants in their study as compared to the present study. But our findings were consistent with the study of Arshi (2017) in which 80–90% survival rate for plants was observed grown over mine overburden dump aided with using efficient microbes with suitable bio-inoculants. In this study, T. grandis and D. sissoo showed 40% and 20% of total ground biomass.

The physicochemical properties of soil determine the soil structure, nutrient enrichment and supply, and microbial diversity in a sustainable way. The process of soil development greatly differs between virgin soil and degraded land as in the case of the present study. The results obtained in the present study are presented in Tables 1 and 2. Initially, the mine soil has high bulk density as compared to newly developed soils (1.44 ± 0.04 g cm−3), but after 25 years, it was decreased to 1.22 ± 0.11 g cm−3 which may be attributed to improved physicochemical and microbiological characteristics of mine spoil. Similarly, the water holding capacity of soil largely influences the plant growth and survival, and consequently, increased WHC was found in the present study, i.e., from 29.80 to 51.20%. In terms of organic carbon enhancement in the treated soil, the increase was up to 6.01 g kg−1 only for the first 6 years, but later, it peaked to 145 ± 13.5 g kg−1. The results for bulk density, water holding capacity, and porosity were also statistically different (p < 0.05) when a comparison was made between initial and final values. Improved nutrient cycling in newly formed soil further showed high availability of total nitrogen, soluble cations, total phosphorus content, and the available potassium levels (Table 1) which indicated that amelioration with ETP sludge and press mud was quite considerable. Although the pH of new soil was more or less neutral (6.9 to 7.4), the nutrient availability was increased by many folds. Significant difference was also found in the pH values for manganese spoil dump; however, no difference was found for coal mine spoil. The trend of changes in physicochemical and biological status of soil is also shown in Figs. 5 and 6. Similarly, significant difference was found among the parameters such as total, nitrogen, total phosphorus, total potassium, and organic carbon (p < 0.05) for both manganese and coal mine spoil.

Fig. 5
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Changes in physical parameters A NPK status and organic carbon B of soil over the duration of 25 years on manganese spoil

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Fig. 6
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Changes in Physical parameters A NPK status and organic carbon B of soil over the duration of 25 years on coal mine spoil

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Besides that, inoculation with biofertilizers and organic matter maintained the optimum microbial populations in soil which performed the fundamental functioning of litter decomposition, ideal nutrient cycling, and fundamental plant growth promotion. Final result obtained in terms of improved plant growth, soil property enhancement, nutrient enrichment, and biodiversity confirms that mine spoil restoration using organic amendments is an appropriate strategy for degraded land rehabilitation within a short span of time (Figs. 7 and 8). A review of Festin et al. (2019) also evaluated that the feasibility of organic amendments to promote plant and animal colonization of mine wastelands and successful restoration of mine spoils in Kenya, South Africa, and Ghana were successfully achieved. However, to accomplish the development of a self-sustainable ecosystem on degraded lands, choosing the specific tolerant plant species against various stress conditions such as metal contamination, drought, and nutrient stress is a major prerequisite. Likewise, in the present study, T. grandis, C. siamea, D. sissoo, D. strictus, and A. nilotica showed higher stress tolerance capacity and simultaneously developed huge amounts of soil organic matter and plant biomass.

Fig. 7
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Observed final plant heights (cm) in different treatments at coal A and B manganese spoil dump

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Fig. 8
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The lush green forest development on the mine spoil dump

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Conclusions

Organic waste (ETP sludge and press mud) amendments or treatments (OWT) to restore mine spoil dumpsite provided the optimum nutrient status of soil and therefore promoted accelerated establishment and colonization of land forming a vegetative plant cover. In addition, microbial strain addition enhanced the functioning of biogeochemical cycles and resilience efficiency of degraded lands like mine spoils thereby increasing the vitality of plants to a greater extent. Such promising outcomes can help in the extensive management and rehabilitation of degraded lands. The OWT allows the economic exploitation of waste materials by promoting the reuse and is an inexpensive restoration strategy mitigating both waste-related problems and nutritional ameliorations to degraded lands or sites. Reclamation of mine degraded land can be considered as a potential carbon sink thereby helping in mitigation of environmental adversities in terms of increasing greenhouse effects and development of wastelands created due to various anthropogenic activities. At this present state, there is a need to encourage remediating such landscapes using tolerant trees and crop plantations along with microbial inoculations. Such practices are repetitively required to address various threats associated with mine-contaminated sites and develop suitable strategies.