Soil is a very important and essential material of the environmental ecosystem which plays a crucial role in plant growth and crop production, and also has vital roles that affect human health. In present society, increased industrial activities since the Industrial Revolution have led to a continued increase in environmental pollution and soil pollution every year. Remediation of contaminated soils are implemented by applying various remediation technologies based on the site characteristics and pollution level, however, chemical, physical, and biological changes and different soil properties exist in remediated soil according to the remediation technique applied. Remediated soils are reused depending on occasion and purpose, but it is hard to reuse for agricultural use because remediated soil has the concept of urban soil and the characteristics of natural or agricultural soil. In this present time, the entire world is facing a serious agricultural crisis due to issues concerning climate change, global warming, soil degradation, reduction of agricultural land, and food security. From now on, it needs to realize remediated soil as a valuable resource, and to find a solution for its agricultural reuse. Therefore, this study was conducted 1) to investigate changes in remediated soil properties and assessment of soil quality as affected by various organic soil amendments including livestock manure compost (LC), charcoal (CC), and biochar (BC), 2) to evaluate the sorption reaction of selected ions in the remediated soil-water systems using inorganic fertilizer as phosphorus fertilizer, and 3) to determine the adsorption-desorption equilibrium of selected ions in the biochar treated remediated soil-water system as influenced by monopotassium phosphate application.Chapter 1. Improvement of Quality and Properties of Remediated Soils using Various Soil AmendmentsThis study was carried out to evaluate soil quality indicator and changes in soil properties for improving remediated soil contaminated with petroleum as influenced by the different organic soil amendments. Two different remediated soils, remediated soil A previously contaminated with petroleum hydrocarbons (RSPA) and remediated soil B previously contaminated with petroleum hydrocarbons (RSPB), were used in this study. RSPA and RSPB were alkaline soils with up to 8.5 of soil pH, very low soil organic matter (SOM) contents and available phosphate (available P¬2O5) concentrations, and very high exchangeable Ca concentrations. Thus, they had very unfavorable soil conditions for crop growth. Natural reduction or degradation of total petroleum hydrocarbons (TPH) occurred even after remediation, therefore, it appeared there should be no concerns of contamination from TPH. The properties of remediated soils were changed with LC, CC, and BC applications. SOM contents were increased with all the treatments. In particular, SOM in RSPB was increased to maximum 19.9 g kg-1 with BC 5.0% treatment, which was 2 times higher than that in RSPA and RSPB Control soil. Also, available P2O5 concentrations increased to 24.9 mg kg-1 (RSPA, 16-week), and 17.5 mg kg-1 (RSPB, 32-week) with BC 5.0% treatment. However, available P2O5 concentration in the remediated soils was very lower than that of optimal value for cultivating crops suggested by National Institute of Agricultural Science at Rural Development Administration in Republic of Korea. Exchangeable Ca concentration decreased in RSPA and RSPB with BC 5.0% application. On the other hand, soil pH and exchangeable Ca were significantly negatively correlated with available P2O5 (p < 0.01) and available P2O5 (p < 0.01), respectively. The soil quality indices were RSPA Control (mean 39.0), RSPA BC5 (mean 56.4), RSPB Control (mean 40.0), and RSPB BC5 (mean 55.2) in assessment of soil quality. The highest soil quality index was found in the remediated soil with BC treatment. The remediated soils require immediate solution for the problems of pH, Ca concentration, and phosphate concentration, and thus should need systematic and continuous managements.Chapter 2. Sorption of Selected Ions in Remediated Soil as Affected by Different Phosphorus FertilizersThe remediated soil was very poor in quality. It had problems with pH, calcium and phosphate. The inorganic fertilizer has a fast-acting effect on the nutrient supply, and thus it might be the right choice if soil improvement is needed for urgent. In this study, monoammonium phosphate (MAP, NH4H2PO4) and diammonium phosphate (DAP, (NH4)2HPO4) were selected as ammonium phosphate type. Monopotassium phosphate (MPP, KH2PO4) and dipotassium phosphate (DPP, K2HPO4) were selected as potassium phosphate type. Sorption interaction of selected ions in the remediated soil-water system was investigated. Adsorption and desorption behaviors of ions are very important to obtain useful information related to supply of plant nutrients. In the remediated soil treated with MAP or DAP solution, the concentration of potassium (K) in soil solution increased with increasing the fertilizer concentration because of the exchange of K+ with NH4+ in the soil. Calcium (Ca) ions in the soil are affected by MAP and MPP in two different stages. At the first stage, the Ca ions tend to be precipitated as insoluble calcium phosphate compound; at the second stage, soil solution pH decreased with increasing the amounts of MAP and MPP applications. Magnesium (Mg) ion showed synergetic dissolution characteristics with Ca ion. In relationships between K and MPP or DPP in the remediated soil-water system, the buffering power (BP) of K was relatively low (97.4) and its bonding energy was high as 13.79 with MPP application because K solubility with MPP was higher than that with DPP due to decrease of pH by reaction with H2PO4-. The concentration of phosphorus (P) adsorbed in the soil was higher with DAP and DPP applications with little change in pH. Phosphorus BP was lowest (84.6), and its bonding energy was highest (15.87) with MPP treatment because of the highest solubility of MPP in the soil-water system. MPP fertilizer is considered to be effective for phosphorus uptake into crops in this remediated soil, and pH 6–7 is well known to be the optimal range for phosphate availability.Chapter 3. Sorption of K and P in Remediated Soil–water Systems Containing Different Biochars as Influenced by Monopotassium PhosphateThis study was conducted to investigate effects of biochar on improving the properties of the remediated soil, characteristics of biochar based on production conditions, and highly fast-acting characteristics of monopotassium phosphate (MPP, KH2PO4) fertilizer for K and P. Alkaline biochar (ABC) and neutral biochar (NBC) were treated to the remediated soil. Sorption characteristics of selected ions and adsorption-desorption behaviors of K and P in soil-water systems containing different biochars were examined. Regardless of biochar characteristics, ABC and NBC applications improved similarly the remediated soil properties. In addition, with the ABC and NBC applications in the remediated soil, there was a slight decrease in pH and an increase in SOM content, T-N content, available phosphate, exchangeable K, exchangeable Mg, and CEC. Biochar treatment contributed to the stabilization of Ca in the remediated soil by reducing exchangeable Ca concentration. Moreover, biochar application improved some physical properties of the soil including reduce of soil bulk density and increase of field water capacity. On the other hand, the remediated soil containing biochar affected the solubility of Ca, Mg and Na with MPP fertilizer solution. The concentration of Ca in soil solution was lowest in the plot with 5.0% of ABC (ABC50) treatment, and the concentrations of Mg and Na in soil solution were lowest in Control soil. The highest buffering power (BP) of K (73.1) was observed in the Control soil with high K adsorption, and the biochar treated soil had the lowest BP of K than Control soil in soil-water system. The highest value (98.4) phosphorus BP observed in the Control soil with high P adsorption. The remediated soil with 5.0% of NBC (NBC50) treatment had the lowest BP value (37.2). Therefore, the remediated soil with NBC 50 is expected for long-term P supply to crops.