The effect of compost on the growth of forest plants in the gold mine tailings of PT. Kasongan Bumi Kencana, Central Kalimantan, Indonesia

Mining activities is consequence of development which will result in ex-mining land, causes of environmental changes include chemical, physical and biological. Physically, the land is damaged, the top soil layer become sand, gravel and granite. Chemically, land not longer provide nutrients for plant growth. Biologically, the less of microorganisms especially decomposers. Revegetation is an effort to improve mine land to increase biodiversity, restore landscape aesthetics, control erosion and runoff. The aims of this study to determine the potential growth of Shorea balangeran, Combertocarpus rotundatus, Melaleuca cajuputi and Alstonia scholaris by applying compost to a gold mine’s Tailing Storage Facility (TSF); 7 year (Mirah 1) and 1 year (Mirah 2). The results of the study on TSF Mirah 1, the percentage of growth M. cajuputi and A. Scholaris was 100%, the highest average height and diameter was M. Cajuputi (MeanH+SD-H) 166.70 + 32.16 cm and (MeanD+SD-D) 1.35 + 0.62 cm. The TSF Mirah 2, the percentage of growth S. balangeran and A. Scholaris was 100%, the highest average height was M. cajuputi (MeanH+SD) 137.30 + 23.43 cm and the highest average diameter was A. scholaris (MeanD+SD-D) 1.23 + 0.38 cm.


Introduction
Indonesia is known as a country that is rich in several potential natural resources from the fields of agriculture, forestry, marine affairs, fisheries, animal husbandry, plantations, mining and energy.The potential for these large natural resources, especially the mining sector, must be managed properly and pay attention to environmental sustainability, so as to contribute to the development of the State and people's welfare [1].The mining industry is one sector that contributes to rapid growth in Indonesia's market capitalization.The total contribution to the Domestic Product Growth (GDP) reached 7.2%.In Indonesia, the GDP value of the mining industry reaches $ 13.8 million and is the highest in Southeast Asia.
This mining activity is undeniable, is part of the consequences of development which results in exmining land, which causes environmental changes, both chemical and physical changes and soil fertility conditions have decreased due to the accumulation of various mining activities [2].Post mining soil conditions show characteristics of physical damage, namely macro porous, sand/gravel/rock texture, dense when dry due to the excavation process, the top soil layer which is rich in organic matter is lost [3,4].Chemically, land can no longer provide positive support for providing nutrients for plant growth.Biologically, the reduction of soil microorganisms, especially decomposers, 1253 (2023) 012115 IOP Publishing doi:10.1088/1755-1315/1253/1/012115 2 causes the land to become infertile.Ongoing mining activities cause land degradation, soil quality decreases, topsoil is lost, the ability to hold water is low, very poor in nutrients and the area of critical land continues to increase, plant growth and development is hampered and productivity is very low [5].
The drastic change in land after mining activities is a very serious impact and must be addressed immediately.The quality of this ex-mining land must be improved through reclamation activities which are expected to return the land to its original state [6].Improvement of ex-mining land can be done by improving the physical, chemical and biological properties.Improvement of physical properties is carried out by adding soil enhancing ingredients such as organic matter, minerals and biological agents.Organic material can come from manure, garbage or compost [2].Organic materials tend to form strong structures that are stable and stable.In a strong structure there is a good balance between air and soil water as a medium for dissolving plant nutrients so that this strong structure is an excellent structure for plants [7].In this study tried to use compost as a nutrient for revegetation of mine land with several types of forest plants.

Study area
PT Kasongan Bumi Kencana (KBK) is a gold mining company located in Mirah Kalanaman Village, Central Katingan District, Katingan Regency (Figure 1), which has been operating since 2012.Gold ore processing produces waste in the form of sludge with characteristics of 60% water and 40% solids which are collected in a single disposal site called a tailings dam.Mud contains potentially reactive minerals, pyrite when oxidized causes the formation of acid mine drainage and metal leaching.Rock waste is stockpiled in disposal piles and tailings are stockpiled in final storage facilities or known as tailings storage facilities (TSF).Since 2013 PT KBK has been actively carrying out reclamation by revegetating the disposal area with pioneer plants including Albizia falcataria, Enterolobium cylocarpum Griseb and Samanea saman.During 2018-2020 PT KBK in collaboration with SEAMEO BIOTROP IPB planted tailings areas; at wet area the use test plants were Ipomoea aquatica Forsk, Eichhornia crassipes and Piscia statiotes but these three species did not grow well.At dry areas the plants tested were Shorea balangeran, Alstonia sp, Combretocarpus rotundatus, Melaleuca leucadendra, Melaleuca cajuputi, Anthocephalus cadamba, Anthocephalus macrophyllus and Metroxylon sago without the addition of organic matter.As a result, the growth of three types of plants; S. balangeran, Alstonia sp and C. rotundatus did not grow well (stagnant) and some were stunted while Melaleuca leucadendra and Melaleuca cajuputi could grow well.To find out more about the growth of some of these forest plants, it is necessary to conduct research by adding compost as a nutrient for plants.
This research was conducted at two of PT KBK TSF areas; (1) TSF Mirah 1 which is a 7 years old tailings area and (2) TSF Mirah 2 which is a 1-year-old tailings.The research was conducted for 7 months (April -October 2022).

Research design
The TSF plots Mirah 1 and Mirah 2, were made 4 subplots with size 3 x 3 m, repeated 2 times, so each plot has 8 subplots.Each subplot planted 4 tree sampling of S. balangeran, C. rotundatus, M.cajuputi and A. scholaris, planted in the planting hole; where previously given by 7 kg of compost.The composition of the compost is Chromolaena leaves, cow manure, sawdust, EM4, sugar and water.Observations were made once a month on the variable life percentage, height gain and diameter increase.
Soil samples on TSF Mirah 1 and TSF Mirah 2 plots before planting and composting (initial soil) were taken randomly at a depth of 0-20 cm, then soil samples after planting and composting were also taken for laboratory analysis.Analysis of soil physical and chemical properties includes texture of 3 fractions (sand, clay and dust), pH, C organic, N total, available P and K.

Statistical analysis
Analyze the data of percentage life, average heigth gain and average diameter of seedling using Microsof Exel.The results of the analysis are made in the form of tables and graphs.

Initial soil analysis and after composting
The results of the analysis of soil physical and chemical properties before planting and composting (initial soil) on TSF Mirah 1 and TSF Mirah 2 are presented in Table 1 and after planting and composting are presented in Table 2.The results of the chemical analysis of the initial soil (Table 1) and after composting (Table 2) on tailings Mirah I showed that pH (H2O), pH (KCl), total N, K-dd did not change too much, phosphorus was also very low, due to the sandy soil texture that have high porosity, P will be leached little by little [8].The source of P in the soil comes from minerals apatite and the decomposition of organic matter [9].Further explained that a low soil P2O5 content indicates low organic matter and minerals containing P.
C-organic value plot Mirah 1 showed a slight increase, the initial C-organic it was 0.28% and after applying compost the S. balangeran subplot was the C. rotundatus subplot was 0.21%, the M. cajuputi subplot was 0.31% and A. scholaris subplot was 0.32%.C-organic plays an important role in 6 shaping the soil structure so that it becomes stronger and plants can easily get nutrients.The addition of soil organic matter plays an important role in supporting soil fertility [10].The effect of the addition of C-organic was also seen in the soil texture, after the application of compost the texture of sand decreased, the texture of dust and clay increased in each subplot (Table 2), even though the addition was very small it had a good effect on the growth of plants, especially M. cajuputi (Figure 2) with a survival are 100%, average height (MeanH ± SD-H) 166.70 ± 32.16 cm and average diameter (MeanD ± SD-D) 1.35 ± 0.62cm.In contrast to the C. rotundatus subplot, which had very low growth and survival life only 37.5%.C. rotundatus is a pioneer species in peat swamp forest and grows well in flooded conditions, a natural environment in peat swamp forest ecosystems [11,12].C. rotundatus grows well with low mortality with an average height gain of 27-255 cm -1 y -1 under open conditions, low humidity and high soil temperature [13].
Initial soil chemistry analysis (Table 1) and after composting (Table 2) on tailings Mirah 2, that all elements analyzed in each subplot did not change, even the P content was so small, so that plant growth is not optimal.P is needed to stimulate the absorption of nutrients through increasing the number of nodules on the roots so as to increase plant growth [14].The C-organic value showed an increase, although only slightly, from the initial analysis of C-organic was 0.05%, then after composting the average C-organic value increased to 0.20% in the S. balangeran subplot, 0.16 % in the C. rotundatus subplot, 0.13% in the M. cajuputi subplot and 0.24% in the A. scholaris subplot.The application of compost to the plot Mirah 2 did not change the soil texture, causing plant growth to be small compared to the plot Mirah 1.The average height was M. cajuputi (MeanH ± SD-H) 137.30 ± 23.40 cm but the percentage of survival was 87.5%, while the higher diameter was A. scholaris (MeanD ± SD-D) 1.23 ± 0.38 cm and the percentage of survival was 100% (Figure 3).
The high sand content causes the soil to not be able to store more water.Low water holding capacity causes many dissolved nutrients to be lost through leaching, poor N in the form of NO 3-and NH 4+ [15].Conversely, the finer the texture of the soil, the greater the capacity to store water [16].In addition, in the tailing Mirah 1 area growing adaptive species such as Typha angustifolia and Cyperus sp, where as in the tailing Mirah 2 only a few, this indicates that tailing of Mirah 1 already contains soil organic matter as a source of nutrients for plants.

Conclusion
Compost application has a good effect on plant growth, especially at Mirah 1 subplot M. cajuputi with a survival are 100%, average height (MeanH ± SD-H) 166.70 ± 32.16 cm and average diameter (MeanD ± SD-D) 1.35 ± 0.62 cm.Plant growth in Mirah 1 and Mirah 2 was less than optimal due to washing and possibly caused by the insufficient dose of compost.To maximize compost application, it needs to be accompanied by ground cover plants (Legume Crop Cover /LCC) to help improve soil structure.

Table 1 .
Analysis of chemical and physical properties of initial soil.

Table 2 .
Analysis of chemical and physical properties of soil after composting 3.2.Average height, diameter and survival of plantsAverage growth of S. balangeran, C. rotundatus, M. cajuputi and A. scholaris on TSF Mirah 1 and TSF Mirah 2 is presented at Table3, Figure2 and 3.

Table 3 .
Average height, diameter and survival plants.