## 1 Introduction  
Biomass from the agricultural sector is composed of agricultural wastes such as crop residues and fringing trees. Researchers have shown that agro-biomass derived carbon materials such as biochar are one (1) option for carbon sequestration as well as the reduction of greenhouse gas emissions. It is estimated that Korea produces 50 million tons of organic waste from agriculture every year [1]. Thus, to address concerns about climate change, carbon sequestration using biomass conversion technology should be prioritized, since it has already become feasible in Korea. Biochar consists of multi-porous and carbonaceous material obtained from biomass conversion technology under limited oxygen. It consists of non-degradable carbon with double bonds and an aromatic ring that cannot be broken down by microbial degradation [2]; it could be applied for several purposes [3]. However, 30% of biochar is lost due to wind, while 25% is lost due to runoff water during spreading in cultivation areas [4]. It has been suggested that Biochar's effects come from a plant's adsorption and retention abilities vis-a-vis the available nutrients [5]. Nitrogen fertilizers have been chemically transformed through mineralization, ammonification, nitrification, de-nitrification, and immobilization in soil [6; 7]. Biochar from rice hull through biomass conversion technology was reported to have 0.498 mg g\({}^{-1}\) of maximum absorption capacity of NH\({}_{4}\)-N, which can prevent nitrification [8]. Biochar from holm oak tree increased NH\({}_{4}\)-N adsorption in sandy Actisol, but had no effect on NO\({}_{3}\)-N adsorption in the column experiment [9]. However, the maximum adsorption of NH\({}_{4}\)-N in the biochar pellet is 2.94 mg\(\cdot\)g\({}^{-1}\), and lettuce yield was enhanced by approximately 13% relative to the control [10]. When biochar pellet is applied to the soil, the application of chemical fertilizers is still needed to enhance crop productivity. Previous studies on the characterization of the NH\({}_{4}\)-N adsorption capacity of biochar pellets recommends the mixing of biochar with compost containing nutrients before the soil application [10; 11]. Phosphorous (P) is essential for maintaining profitable crop production [12; 13]. However, it might cause eutrophication in lakes and ponds, thereby destroying the ecosystem [14]. In recent years, attention for biochar has increased because of its absorption abilities [15; 16]. Manure-derived biochar increased the maximum uptake of nitrogen (N), phosphorus (P) and potassium (K) by ryegrass by 66.4%, 161% and 210%, respectively [17]. Biochar from tree prunings enhanced P use efficiency from organic P fertilizer more than the chemical fertilizers for both corn and wheat crops [18]. Silicon (Si), on the other hand, is important to the strength of cell walls and defense against diseases, as well as to enhancing the uptake of other nutrients, and increasing tolerance to drought, salts, and extreme temperature stresses [19; 20; 21]. Silicon plays an important role in improving the rice yields. It is a potent stimulator of photosynthesis [22]. Biochar is not suitable for crop cultivation in a practical view because it does not contain sufficient amounts of plant nutrients for crop production. Biochar pellets are an efficient way to decrease field handling costs and to significantly reduce biochar loss during soil application [23]. For soil incorporation, poultry litter was mixed, pelletized and slowly pyrolyzed to produce biochar pellets [24]. However, little information is available on blended biochar pellets as a slow release fertilizer, which is required to allow nutrients to flow slowly from the soil during the cultivation period. It supplies most nutrients into the crop without leaching and denitrification losses [25] to increase profits and minimize environmental destruction [26]. The predictions of the used model confirmed that Michaelis-Meten-type kinetics is probably the most dominant mechanism for the leaching of heavy metals from cement-based waste forms.