Biochar and Specific Organic Fertilizer for Post-Mining Reclamation Treatment

Mining activities are not just digging, loading and transporting, but environmental sustainability is also an important thing that must be considered. Even post-reclamation has become an obligation for mining companies with severe sanctions if neglected. Environmental damage due to mining if left unchecked will become a serious environmental problem such as natural disasters, and become a bad legacy for future generations. This means that post-mining reclamation must be carried out properly or adequately so that the negative impact on the environment can be minimized or even eliminated. Reclamation planning and implementation needs to be done well so that the reclamation goals can be achieved.

Low fertility on post-mining land is indeed a separate problem for revegetating the land. When a mining company has good management of overburden (OB) and top soil so that it can be returned (backfill) to the former mining pit (void) as before, the decline in soil fertility can be minimized. But if the management is bad, the fertility of the soil will drop drastically or be severely damaged so that in these conditions certain treatments need to be carried out to restore, improve or increase the fertility of the soil. The condition of land that has low fertility or is like barren land is almost the same as sandy land. In general, coastal sandy land has the following characteristics: sandy soil texture (90%), granular soil structure, loose consistency, low nutrient content, low soil ability to store nutrients, very fast permeability, drainage and infiltration, porous (majority with mesopores and macropores, and less of micropores), low water holding capacity, low soil ability to support plant growth and relatively high salt content or is a marginal land for agriculture or plant cultivation, so the treatment approach on sandy land with post-mining land is an effort effective approach.

Agriculture or cultivation of sandy land can be done for both seasonal and annual crops, the same goes for post-mining land. Factors of effectiveness and efficiency need to be done to get optimal results such as the type of nutrient and its amount, water requirement and so on. Conditioning the land so that it can hold water and nutrients must be done so that the added fertilizer can be utilized properly. Minimum input so that production costs can be reduced or economic factors are other important things. With post-mining land areas that can reach thousands of hectares, the input in the form of quality fertilizer is a must. In addition to inorganic fertilizers as macro elements, organic fertilizers as a provider of micro elements also need to be added. Specific organic fertilizer according to land conditions and plant needs can be made for this purpose. The use of compost with volumes ranging from 20-30 tons/hectare can be significantly reduced by using this specific organic fertilizer.

Sandy soils generally have high P and K content. The function of organic matter, in this case manure, can stimulate the availability of P nutrients that have accumulated in the sandy soil in the form of total P, so that available P becomes greater. With the availability of P, the available K is also greater, because P interacts with K. Amelioration technology to increase soil fertility is needed. Amelioration itself is an effort to improve soil fertility through the addition of certain materials. Amelioran is a substance that can increase soil fertility by improving physical and chemical conditions. Biochar as a soil amendment will be effective for this purpose, even when compared to other soil amendments, biochar has many advantages, one of which is being able to last or not decompose in the soil for hundreds of years. While increasing the efficiency of using biochar is by designing slow release fertilizer (SRF) so that the release of fertilizer is according to plant needs or can be used by plants optimally.

Plants are composed of 92 elements, but only 16 are essential for their growth and development. Of the 16 elements, elements C, H, and O are obtained from air and water (in the form of CO2 and H2O), while 13 other essential mineral elements are obtained from the soil and are generally classified as "nutrients". There are 6 macro nutrients namely N, P, K, S, Ca and Mg. These macro elements are needed by plants in large quantities with a critical content (value) between 2 – 30 g/kg dry weight of plants. These macro nutrients are divided into two, namely primary nutrients (N, P, K) and secondary nutrients (S, Ca, Mg). Primary nutrients are provided in the form of all types of plants and all types of soil. Meanwhile, secondary nutrients are only for certain types of plants and certain types of soil. While micro nutrients consist of 7 elements consisting of 5 elements which are metals namely Fe, Mn, Zn, Cu and Mo, and 2 non-metallic elements namely Cl and B. The need for micro nutrients is relatively small ranging from 0.3 – 50 mg/kg dry plant weight. The combination of macro fertilizers and specific organic fertilizers will maximize plant growth.