Bioremediation of Ex-Mining Soil with the Biocompost in the Incubation Experiments

A process called bioremediation can be used to turn abandoned mining sites into useful agricultural land. An alternative to enhancing the quality of the ex-siltstone mining soil so that it can be used again as agricultural land is the application of biocompost fertilizer. Tis study intends to investigate how biocompost might enhance the ex-siltstone mining soil’s quality in incubation treatments. Te composition of biocompost used in this study is ingredient I: (a) cow manure � 50%; (b) chicken manure � 30%; (c) sand � 10%; (d) bacteria (bioactivator) � 10%; ingredient II: ingredient I is mixed with cow manure in a composition ratio of 1: 2. Te ex-mining soils were gathered in the ex-cement mining region of Lhoknga Subdistrict, Aceh Besar District (5.45 ° N, 95.2 ° E). Incubation experiments were conducted in incubation pots (approximately 5kg per pot) that were randomly placed in a greenhouse using a 4 × 4 factorial completely randomized design (CRD) with three replications. Te frst factor is the ratio of ex-siltstone mining soil: biocompost, which consists of four levels of comparison: control (ex-mining soil not incubated), 1:1 (50:50), 1 :2 (33: 67), and 1 :3 (25:75). Te second factor is the incubation period, which has four levels: 0, 2, 4, and 6weeks with 48 experimental units. Indicators of the impact of biocompost on the physical and chemical quality of ex-siltstone mining soil were examined. Te result shows that bioremediation of ex-siltstone mining soil with biocompost application improves the quality of ex-siltstone mining soil by decreasing bulk density and permeability and also increasing porosity, decreasing soil pH from alkaline to neutral, and increasing soil organic C, total N, available P, and total K. Te incubation period of ex-siltstone mining soil infuences the changes and dynamics of the soil’s chemical properties.


Introduction
Land and environmental degradation in mining areas can become a major issue if not properly managed.Indonesia's mining area is estimated to be 93.36 million hectares, and this mining area is growing in line with government policies that encourage mining exploration [1].Tis condition is inversely proportional to the shrinkage of agricultural land [2].Te addition of mining areas will exacerbate land damage and cause critical land to expand.Mining for cement is one of the causes of critical land [3].Degradation or deterioration of mining land causes changes in the landscape, physical, chemical, and biological soil conditions, microclimate, and changes in fora and fauna [4,5].During the process of open-pit mining, all vegetation and topsoil are removed, the soil fertility in each horizon is shufed, and chemical, physical, and biological conditions rapidly deteriorate [6].
If the treatment of open-pit mining is not careful, it appears that the issues that may arise include changes in landforms, harm to the soil structure, and loss of topsoil.Te biota of degraded land typically difers from the original ecosystem community, and the richness of fora, fauna, and microbial species tends to decline.Additionally, the drainage system is hampered by the emergence of excavated shells, which makes it challenging to use the property in the future [7].Te arid and uneven soil surface conditions (expanses), high soil pH (alkaline), many rocks with coarse soil texture, and very dense soil conditions due to the passage of heavy equipment (because mining activities are still on-going/ active) were the obstacles discovered during the preliminary survey at the former silt mine site.As a result of machine activity during the mining process, a dense surface soil layer is created, which leads to the closure of soil pores [8].Te soil's composition will be harmed by issues discovered near old siltstone mines as a result of mining activity.By removing topsoil to access a deeper layer of mining material, the topography and soil composition of the surface soil are altered, resulting in harm to the physical and chemical qualities of the soil [9].Te loss of the heap's soil structure also reduces the soil's stability by altering the distribution of soil pores, which are crucial for holding water, destroying soil pore channels, which are crucial for allowing water to permeate the soil, and raising the risk of erosion.Te soil's ability to support plant development will be reduced by the loss or sinking of fertile topsoil.When compared to intact soils, topsoil loss causes in lower yearly yields and inferior physical qualities (aeration, permeability, and aggregate stability) [10].
Aceh Province will have 28 IUPs (mining business permits) operating in various areas of Aceh in 2022.Tis area's mining business felds include gold, petroleum, cement, coal, and minerals B and C. Te mining area in Aceh Province is estimated to be 70,761.10ha [11], and it is estimated to be around 2,193.08 ha in Aceh Besar district [12].Siltstone mining is one of the mining areas in this area, and it is processed into "Portland" as a raw material for making cement.Open-pit mining is one method of extracting the siltstone used as the primary building block of cement.Te former mining terrain can be described as in a bedrock condition due to open-pit mining.If this is permitted, mining activities will result in more signifcant quantities and intensities of environmental harm, expanding the area of essential land.In the vicinity of previous open-pit mining systems, including old mines for cement raw materials, damaged land from former mines is typically challenging to reclaim and abandon [13].
Te following are the quick steps in mining siltstone: (a) clearing the land of bushes and shrubs to make mining siltstone easier, (b) stripping/removal of top soil between 2 and 3 m and then stockpiled in a certain location using an excavator, (c) drilling is done to make it easier to take apart the materials, (d) blasting: siltstone material is destroyed by blasting so that it is easier to transport, and (e) loading: when loading, the blasted stone is immediately loaded into a dump truck and driven to the stone crushing plant using an excavator tool (Siltstone Crusher).
Mining activities cause vegetation loss, soil horizon damage, compaction, and damage to soil texture and structure, all of which are essential soil physical properties for plant growth [14].Because the top soil layer (topsoil) is relatively good and the layer below it has been taken or removed, the subsoil layer in the form of horizon C or a layer of soil parent material and bedrocks occurs [15].Furthermore, heavy equipment trafc during the mining and stockpiling processes contributes to the formation of a dense surface soil layer, which leads to the closure of soil pores, a process known as surface sealing and crusting [8].Tese former mining sites are classifed as damaged land and must be reclaimed or rehabilitated.Ex-mining land typically has a high density and has lost soil constituent components such as organic matter and clay content (colloids), leaving a soil layer that is less fertile and critical due to damage to its physical and chemical properties [5,16].
In general, the reclamation of ex-mining soil entails converting damaged land caused by the mining process into productive land or ecosystems to create a useful landscape and fulfll the purpose of reclamation, such as converting it into fertile agricultural land [17].Mine reclamation is a routine part of modern mining practices in developed countries such as the United States and Europe [18].For developing countries, the approach to the reclamation of exmining land can be made in situ or ex situ, namely, through the use of bioremediation and phytoremediation methods [19][20][21].Using biocompost amendments enriched with microorganisms is one of the simplest bioremediation methods [22].
Biocompost is a type of biological fertilizer that combines diferent types of bacteria in one carrier to deliver nutrients and boost crop productivity [23].Biocompost is an organic material used as a soil supplement that has been enhanced with microorganisms.Biodegradable processes are brought about through the use of biocompost.A process called biodegradation uses bacteria to transform toxic chemicals into a simpler form and restores an ecosystem that has been harmed by them.According to [24], biodegradation is the process by which microorganisms are able to break down or degrade both synthetic and natural polymer molecules.Lignin and cellulose are examples of natural polymers, whereas polyethylene and polystyrene are examples of synthetic polymers.
Rice straw and animal manure are two examples of the agricultural and livestock waste that is typically used to make biocompost.According to [25], adding FMA and organic fertilizer (compost) can improve soil chemical properties and increase the growth of sunfower plants.Te benefts of using biocompost over other forms of biofertilizers include the fact that the author's biocompost is well populated with microorganisms (decomposer bacteria).Making biocompost also does not take a long time because it uses aerobic methods in an open atmosphere and the decomposition process does not require a lengthy fermentation period so that the biocompost can be placed directly to the soil or land after the composition of the necessary raw materials has been mixed.Tis organic fertilizer (biocompost) is excellent because it may assist plants by providing nutrients they need, affordable, of high quality, and ecologically friendly.It can also improve soil structure, soil aeration, soil porosity, and the composition of microorganisms in the soil [26].so it can also be used as a soil amendment to improve soil properties as a good planting medium.Te purpose of this research is to improve the physical quality of ex-mining soil by modifying the composition of the growing media and the incubation stage of biocompost fertilizer.
Since the purpose of incubation is to ensure that the reaction between organic matter and soil proceeds smoothly, incubation treatment must be carefully examined in order for plants to have access to nutrients in the future.According to [27], incubation is done to give microorganisms a chance to grow and metabolize in order to break down the content of organic matter into inorganic compounds that would subsequently be absorbed by plants.Te results of the study of [28] showed that the application of biocompost was able to lower the pH of the tailings from 9.1 to 6-7 in the time period 30 days after incubation.Tis is due to the fact that the formation of organic acids occurs as a result of the decomposition of organic matter.Some chemical properties such as organic C, N, P, and K which were originally low also increased after being incubated for 30 days.Improved soil pH is a very important factor for increased plant growth.With regard to the use of amendment materials in improving the pH of the soil of former siltstone mines, it is possible to increase soil biological activity so that the decomposition of soil organic matter increases and ultimately afects the increase in N, P, and K elements [29].

Materials and Methods
Tis study was carried out in the Green House of Abulyatama University's Faculty of Agriculture in Aceh Besar District, Aceh Province, Indonesia.Te research was carried out between February and July of 2021.Te basic soil left behind from the mining process is the soil that is the subject of bioremediation experiments (at a depth of 10 m above the ground level after mining).Although there is still some soil in the siltstone area's bottom soil, silt rock particles with a coarser texture predominate there.Te biocompost used is prepared by the researcher/author himself.Biocompost fertilizer made from cow manure, chicken manure, sand, and decomposing bacteria is used (bioactivator).Te composition of biocompost used in this study is as follows: ingredient I: (a) cow manure � 50%; (b) chicken manure � 30%; (c) sand � 10%; (d).bacteria (Bioactivator) � 10%; ingredient II: ingredient I is mixed with cow manure in a composition ratio of 1 : 2.
Te research location of ex-siltstone mining soil is located at a cement processing plant in Lhoknga Subdistrict, Aceh Besar District.Figures 1 and 2 depict the ex-mining location.A mining company that has long been operating in Aceh Province is the research location with the type of minerals in the form of siltstone (Figure3).Te mining area is in the Lhoknga Subdistrict, Aceh Besar District.Te mining location is 17 kilometers from Banda Aceh City.Mining operations have been on-going since 1980, producing ex-mining land that requires reclamation (Figure 4) in an area of 94 located at the coordinates 5.45 °N, 95.25 °E.Te environmental conditions surrounding the production operation permit area are hills at the foot of the Northern Bukit Barisan Mountains formed by coastal sediment deposits.
Te initial conditions and mining environment in this hill system have been overgrown by tropical forests, but the majority of them have been converted to arable land for nutmeg and young plants.Tere are various types of wood (trees) with very good growth in areas where dense tropical forests still exist.Te siltstone mining operation is situated on the banks of the Krueng Raba River, not far from the beach.Tis area is classifed as Other Use Areas, with the land having use rights and not being included in the protected forest area.Local residents have attempted to use the ex-mining areas in this area but have been unsuccessful due to several obstacles and the need for testing to obtain appropriate management methods.Tis former mining area is now abandoned, and some of it has grown into shrubs [30].
Te ex-mining soil sampling for the experiment was collected from various locations on the mining site (Figure 5), then composited and evenly stirred.Te soil retrieval site used for research tests and the soil taken for examination of the initial soil characteristics are the same.Before the experiment, some soil samples from this area were collected for laboratory analysis to determine the physical and chemical characteristics of the soil.Soil texture, bulk density, porosity, permeability, pH (H 2 O), organic C content, total N, available P, and total K were among the soil quality indicators studied.Soil samples were collected using ring samples for measuring physical properties, and disturbed soil samples were collected compositely at a depth of 0-20 cm for soil chemical analysis.Te soil from the mine site was air-dried for a week before analysis and use in incubation experiments.Samples for preliminary analysis were crushed and sieved through a 10-mesh sieve.
Te experiment was carried out in incubation pots (5 kg capacity per pot) placed randomly in a greenhouse using a 4 × 4 factorial completely randomized design (CRD) with three replications.Te frst factor is biocompost which is given in four levels of comparison, namely, control (exmining soil not incubated), 1 : 1 ratio (50 : 50) or 1.50 litres of ex-siltstone mining: 1.50 litres of biocompost which is equivalent to 300 t•ha −1 of biocompost, 1 : 2 ratio (33 : 67) or 1 litres of ex-siltstone mining soil: 2 litres of biocompost which is equivalent to 446.7 t•ha −1 , and 1 : 3 ratio (25 : 75) or 0.75 litres of ex-siltstone mining soil: 2.25 litres of biocompost which is equivalent to 500 t•ha −1 of biocompost.Te second factor is the incubation period, which has four levels: 0, 2, 4, and 6 weeks, for a total of 48 experimental units.For the pot incubation experiment, air-dried soil from Applied and Environmental Soil Science   Applied and Environmental Soil Science the sample location is sieved with a sand sieve to separate rock or gravel from the soil and then placed in incubation pots.Te basis for determining several doses of biocompost has been tested based on reference [31] and based on consideration of the target soil organic C content of 3-5%.In addition, biocompost is an amendment expected to improve    the characteristics of ex-siltstone mining soil.Te consequence requires a larger dose than if it is only used as fertilizer.
Furthermore, according to the level of treatment, each pot was added and mixed with biocompost in a volume ratio.After homogeneous mixing, pure water was poured into each pot until it reached the feld capacity condition, and the pots were then covered with black plastic to prevent light exposure.Tis soil mixture is then left for 6 weeks, and soil samples are taken from each pot for analysis in the laboratory at weeks 0, 2, 4, and 6 (depending on the incubation period) to determine changes in several selected soil quality indicators, namely, bulk density (BD), permeability, porosity, pH (H 2 O), organic C content, available P, total N, and total K.
Te experimental data were processed using the analysis of variance at the P level (0.05) and the least signifcant diference (LSD 5%) test to determine diferences between the biocompost treatments on soil physical parameters during each incubation period.Soil chemical data are presented as a histogram, and a line graph is used to determine the dynamics of changes in the chemical properties of ex-mining soil due to the application of biocompost.Pearson's correlation analysis was used to determine the relationship between soil quality indicators at each incubation period [32].

Initial Characteristics of Ex-Mining Soil.
Table 1 shows that the characteristics and properties of the ex-siltstone mining soil used for the experiment presented numerous challenges in terms of soil quality.Tese limitations include coarse soil texture (sand), extremely high bulk density (BD) (2.04 Mg•m −3 ), low soil porosity (7.43%), and medium permeability (6.53 cm•h −1 ).Soil with a sand texture cannot bind water and does not form a good soil structure, so it is easily eroded and lacks colloids that absorb water and nutrients [36,37].Soil texture is one of the soil characteristics that greatly infuence the soil's ability to support plant growth [38].To ascertain the association between soil quality parameters at diferent incubation times, Spearman correlation analysis is performed.Table2 shows the best treatment of correlation matrix between several soil chemical properties after incubation experiment and biocompost application.
Te very high BD value indicates that this ex-mining soil has lost its function as a good plant growth medium because the soil becomes solid, making it difcult for roots to penetrate [39] and refecting that the ability to transport water has been decreased and diminished [40].Furthermore, poor porosity indicates that this soil lacks sufcient or balanced macrospore and microspore space, which reduces the rate of water infltration [41] and makes runof more likely [42].Te relatively rapid permeability will have implications for the easy loss of water from the soil solum, reducing the ability to hold water [43].
Based on the physical properties of the soil (Table 1), it is possible to conclude that the physical condition of the exmining soil under study is very poor and that improvements are required.Because soil physics is an indicator of soil and water conservation [38], many researchers are interested in soil erosion and water quality [44].Soil physical properties such as bulk density, infltration, aggregation, and hydraulic conductivity will be afected by land management, which is critical for soil and water conservation eforts [45,46].
Table 1 also shows that the initial soil analysis reveals that this ex-mined soil has a very high pH (alkaline), organic C content, total N, and low available P. Te exchangeable K level is moderate [47].Te chemical quality of the ex-mining soil is not good for plant growth based on its chemical

Biocompost Efects on Ex-Siltstone Mining Soil Physics.
According to the analysis of variance, applying biocompost to the media/soil of ex-siltstone mining signifcantly improved the soil's physical quality by decreasing bulk density (BD) and soil permeability and increasing soil porosity.Te length of the incubation period has an impact on the soil porosity, soil bulk density, and soil permeability.Table 3 shows that the higher the biocompost dose, the lower the ex-mining soil's bulk density (BD).Te best biocompost application on ex-mining soil treatment was at a ratio of 1 : 3 (25 : 75), or 25% ex-mined soil + 75% biocompost.In general, the 1 : 3 (25 : 75) treatment differed signifcantly from the 1 : 1 (50% ex-mining soil + 50% biocompost) and 1 : 2 (33% ex-mining soil + 67% biocompost) treatments.Biocompost application is able to increase BD from a slightly hard condition to being lighter or porous when compared to the BD value before the incubation experiment.Furthermore, Table 4 shows that the average of the porosity of ex-mining soil increased from 7.43% before incubation to 51.68% after the biocompost treatment (1 : 1) and become higher to 52.28% and 52.29 (1 : 3 and 1 : 2 treatments).Tere was the diference before incubation with another treatment ratio of soil: biocompost, but 1 : 3 treatment was diferent from 1 : 1 treatments ratio and there was no diference with 1 : 2 treatments ratio, and there is also a change at incubation periods of 2, 4, up to 6 weeks.
Based on the results of this experiment, it can be stated that the application of biocompost can increase soil porosity from poor or very low to good or medium [48].Te 1 : 3 ratio (25% ex-mined soil + 75% biocompost) had a slightly better efect because it was able to increase higher porosity.Prior to the incubation experiment (Table 1), the permeability of the ex-mining soil was 6.53 cm•h −1 (slightly fast).However, after a week of incubation, the permeability of this soil decreased to 2.55 cm•h −1 (medium) when a 1 : 1 (50 : 50) biocompost was applied.At a higher biocompost dose, namely, 1 : 3 (25 : 75) or 25% ex-mined soil + 75% biocompost, soil permeability decreased to 2.14 cm•h −1 (medium), and there is also a change at incubation periods of 2, 4, up to 6 weeks, but it is still classifed in the criteria medium (Table 5).As a result of the interaction, there was a slightly inconsistent change in soil permeability during incubation, as shown in Table 5. Te application of biocompost at a 1 : 3 (25 : 75) at 2-week incubation times treatment which was 3.62 cm•h −1 slightly lowered the permeability value of the soil.However, it is still within the moderate criteria.Organic matter is very important in improving soil physical properties, such as improving soil structure and increasing soil aggregation into crumbs, which improves permeability and porosity.Improving soil quality means being able to increase and decrease the physical and chemical properties of the soil.
Te changes in the physical properties of the soil following incubation of ex-mining soil with biocompost, as indicated by a decrease in bulk density and an increase in soil porosity and permeability, are a positive impact of biocompost as an amendment material that functions as a soil  Numbers followed by the same letter in the same column were not signifcantly diferent according to the LSD 0.05 test (0.30).
Applied and Environmental Soil Science bioremediation agent.Tis improvement in the physical quality of ex-mining soil occurs because biocompost is a type of organic fertilizer that, in addition to microorganisms [49], contains humus compounds such as humic acid and fulvic acid, which act as agents for the formation of soil aggregates [50] in order to improve soil structure.
With the infuence of this humus compound, heavy clay soils with coarse and strong lump structures will change into a fner structure and crumb consistency, making the soil easier to cultivate and increasing water penetration into the soil [51].Because biocompost is an organic material with a very low BD (0.3 Mg•m −3 ), mixing it with soil reduces the soil BD [52,53].
Low bulk density indicates that the soil or growing media is light, crumb, porous, and high in soil organic matter, which will support plant root growth [54].Te study's fndings [55] revealed that using organic matterbased ameliorants could improve the bulk density and permeability of the tailings soil.Te study in [56] added that the higher the amount of soil organic matter applied, the lower the bulk weight of the soil and the higher the total porosity, lowering the soil's resistance to penetration.Groundwater conductivity decreases as soil density increases; however, in less compacted soils, the bulk density of the soil becomes relatively lower, and groundwater conductivity increases [57].Increased application of organic matter improves soil structure and reduces consistency, increases soil porosity, and decreases soil bulk density [58,59].
One of the functions of organic matter is to produce a high total pore space and a low soil volume weight, which allows water to enter the soil and increase soil permeability [60].Overall, there was a wide range of research data tested, particularly during the incubation period.However, the composition of the planting media with a ratio of 1 : 3 (25% ex-mining soil: 75% biocompost) produced better results because the proportion of organic matter was higher than that of the treatment (1 : 1 or 1 : 2).Te fndings of this experiment are consistent with previous research, indicating that the use of organic amendments includes biocompost and other materials such as biochar [61,62], manure, and a combination thereof.It can improve soil quality in terms of physical, chemical, and biological soil properties [63,64], making nutrients more available for plant growth and development [65].6) show that the biocompost factor and the incubation period, as well as their interactions, have a signifcant efect on the chemical properties of the exmining soil.Tis demonstrates that using biocompost in various ratios can improve soil chemical quality as measured by changes in pH (H 2 O), organic C content, total N, available P, and total K.

Change of Soil Chemical Properties. Te analysis of variance results (Table
Figure 6(a) shows that the pH value (H 2 O) of the exmined soil before incubation had a very high value of 8.40 and included the criteria for being slightly alkaline.Furthermore, after a week of incubation, the soil pH (H 2 O) decreased to 7.40-7.48or became neutral with the addition of biocompost in several comparisons (50 : 50, 33 : 67, and 25 : 75).Tis pH value continued to fall until it reached 7.08 at the end of the incubation period (6 weeks).
When comparing the biocompost treatments, it appears that there is a diference in the levels of biocompost treatment, but the diference is inconsistent.Tis occurs as an efect of the interaction between the ratio of soil: biocompost and the incubation period.Tis interaction efect is thought to be related to the activity of microorganisms found in biocompost in the process of organic matter decomposition.Microorganisms use organic matter (biocompost) as an energy source [63].Te shift in soil pH from slightly alkaline (8.40) to neutral (7.08) demonstrates that biocompost can be used as a material for the bioremediation of polluted soils, including ex-mining soils.Several other researchers have reported that one of the benefts of using biocompost is that it can improve soil chemical properties such as pH [66].
Figure 6(b) also shows that biocompost can raise the organic C content of ex-siltstone mining soil from very low to high to very high status.More specifcally, it appears that the ratio of ex-siltstone mining soil to a biocompost level that has the greatest efect on increasing soil organic C is obtained at 1 : 3 or 25 : 75 treatment, namely, 25% exsiltstone mining soil: 75% biocompost, followed by treatment 1 : 2 or 33 : 67 (33% ex-siltstone mining soil: 67% biocompost).Tese two treatments increased the C content of the ex-siltstone mining soil by 23.7-31.9percent, whereas the 1 : 1 or 50 : 50 treatment (50% ex-siltstone mining soil: 50% biocompost) only increased the C content of the exsiltstone mining soil by 5.95%.
Tis increase in soil C content occurs because biocompost is one of the organic amendments that contain a number of compounds that improve the physical, chemical, and biological properties of the soil [67].Te results of the composition analysis of the biocompost revealed that the C content in this material was 34%.Tis high C content has the potential to supply C to the exmining soil under investigation.Furthermore, increasing the C content of ex-mining soil with biocompost will increase the development and activity of microorganisms, as well as the type and number of soil microbes [68].Te use of biocompost also increased the total N content, available P, and total K of the ex-siltstone mining soil.Figure 7(a) shows that the N content of the ex-siltstone mining soil is very low (0.1%) and increases from 0.22 to 0.46%, classifying it as moderate [47].Te biocompost treatment with the highest total N yield was obtained at a 1 : 3 ratio, or 25% ex-mining soil: 75% biocompost.Tis treatment difered signifcantly from the 1 : 1 (50 : 50) and 1 : 2 (33 : 67) treatments in general.Figure 7(b) shows that after biocompost application and incubation, the soil's available P content increased from 6.0 mg•kg −1 (before incubation) to 159.6 to 197.1 mg•kg −1 .Tis demonstrates that applying biocompost in a specifc ratio to ex-mining soil can increase the available P content of the soil from low to very high.Although there was a statistical diference between biocompost treatments, the diference was not as stark when compared to changes in total N, especially after 2 weeks of incubation.Furthermore, Figure 7(c) shows that the results of biocompost application in each incubation period could increase the total soil K from 9.54 mg K 2 O/100 g (very low) to 13.77 mg K 2 O/100 g (low) at a ratio of 1 : 3 (25 : 75).Based on the results of this incubation experiment, the higher the dose of biocompost, the higher the increase in total N, available P, and total K of ex-siltstone mining soil.
Te increase in total N, available P, and exchangeable K in ex-mining soil incubated with biocompost occurs because biocompost contains a variety of nutrients as an amendment  material, including N, P, K, and other elements such as Ca, Mg, S, and trace elements [69].Microorganisms decompose these nutrients during the incubation process, allowing them to dissolve into the soil solution as available forms such as NO   10 Applied and Environmental Soil Science from dissolving minerals and cations from complex organic compounds, these acids can also act as colloids for ion exchange [73].Figures 8(a) and 8(b) and 9(a)-9(c) show the pattern of changes in several selected chemical properties during the incubation experiment.Te pH (H 2 O) of the ex-siltstone mining soil that was given biocompost after 1 to 2 weeks of incubation decreased dramatically from slightly alkaline conditions to neutral, as shown in Figure 8(a).After that, the changes were relatively stable until a 6-week incubation period.Te pattern of pH changes was similar between the biocompost treatments.On the other hand, after 1-2 weeks of incubation, the organic C (Figure 8 Figure 7(a) also shows that the pattern of changes in organic C content difers greatly between biocompost treatments.Similarly, the pattern of changes in total N (Figure 7(b)) and K (Figure 7(c)) content can be swapped, whereas the available P content parameters are relatively similar across biocompost treatments (Figure 9(b)).Te activity of soil microorganisms in the decomposition process of organic compounds from the given biocompost is related to the diference in patterns and dynamics of changes in soil chemical properties caused by incubation with biocompost [74].Te higher the biocompost dose, the higher the C content, and thus the product of the compound released [75].Organic matter decomposition is closely related to C and N elements.If the remodelled material has a high C content, soil microbes will use N, P, and other elements as a source of nutrients [76], and N will be released back into the soil solution once stable [77,78].According to the fndings of this experiment, intensive reshufing and transformation activity occurred from the frst to the second week of incubation, after which the activity became sloping or stable.Based on these fndings, if the biocompost-treated ex-mining soil is to be used as a planting medium, it should be used after 2 weeks of incubation to avoid N immobilization in plants.Te treatments that can be applied in the feld based on the results of this study are as follows: exsiltstone mining soil and biocompost of ratio 1 : 3 (25% exsiltstone mining soil: 75% biocompost).2) show that there is a signifcant correlation between several chemical properties after ex-siltstone mining soil incubation with biocompost.pH (H 2 O) has a negative correlation with total N (r � −0.66 * ), organic C has a negative correlation with total N (r � 0.59 * ) and total K (r � 0.79 * * ), and total N has a negative correlation with total K (r � 0.79 * * ).

Soil Chemical Properties Correlation. Te correlation analysis results (Table
Te correlation between pH (H 2 O) and total N in exsiltstone mining soil is linearly negative, implying that the higher the pH values of the soil, the lower the total N content of the soil.Tis can be explained by the fact that when the pH of the ex-siltstone mining soil reaches an alkaline criteria, soil microbe development and activity become less active or unfavourable [79], afecting the development of the microbial population [80].Furthermore, there is a positive relationship between organic C, total N, and total K. Tis means that as the organic matter or C content of the ex-siltstone mining soil increases, so does the supply of N and K into the soil, which is also relevant to the positive correlation between total N and total K availability.Nitrogen (N) is a constituent element of organisms that ranges from 3 to 5% in composition, and this N element accounts for 1/ 10 of the C content of organisms in the rhizosphere [81].As a result, as the organic C content increases, so does the N.

Conclusions
Bioremediation of ex-siltstone mining soil with biocompost application improves the quality of ex-siltstone mining soil by decreasing bulk density and permeability, and also increasing porosity, decreasing soil pH from 8.40 (alkaline) to (7.04-7.50),and increasing soil organic C, total N, available P, and total K. Te incubation period of ex-siltstone mining soil infuences the changes and dynamics of the soil chemical properties.Te intensity of changes of ex-siltstone mining soil properties caused by the biocompost application increased during the 2-week incubation period.Te best biocompost treatment for improving the quality of exsiltstone mining soil was obtained at ex-siltstone mining soil and biocompost ratio of 1 : 3 (25% of ex-siltstone mining soil: 75% of biocompost).

Figure 4 :
Figure 4: Visual condition of reclamation area.

Figure 6 :
Figure 6: Te average of pH (H 2 O) and organic C content of ex-siltstone mining soil at each incubation period due to biocompost application.

Figure 7 :
Figure7: Te average of total N, available P, and total K of ex-siltstone mining soil at each incubation period due to the application of biocompost.

Figure 8 :
Figure 8: Te dynamics of changes in pH (H 2 O) and organic C of ex-siltstone mining soil due to the incubation period in each biocompost treatment.

Figure 9 :
Figure9: Te dynamics of changes in total N, available P, and total K of ex-siltstone mining soil due to the incubation period in each biocompost treatment.

Table 2 :
Correlation matrix between several soil chemical properties of ex-siltstone mining after the incubation experiment and biocompost application.
characteristics.Te total N content is approximately 0.11%, or 1.10 g•kg −1 , or 22 kg•N per hectare, while the available P is 6 mg•kg −1 P 2 O 5 , or approximately 12 kg•P 2 O 5 per hectare.Exch.K is 0.3 cmol•kg −1 , which is approximately 117 mg•kg −1 K, or the equivalent of 282 kg K 2 O per hectare.

Table 3 :
Te bulk density value of ex-siltstone mining soil due to the application of biocompost at various incubation periods.Numbers followed by the same letter in the same column were not signifcantly diferent according to the LSD 0.05 test (0.18).

Table 4 :
Te porosity of ex-siltstone mining soil due to the application of biocompost at various incubation periods.

Table 5 :
Te permeability of ex-siltstone mining soil due to the application of biocompost at various incubation periods.

Table 6 :
F test values of several chemical properties of ex-siltstone mining soil after incubation experiments.