Application of humic substances and bottom ash compounds in improving soil quality in limestone post-mining land

Abstract

Limestone mining leaves the ex-mine land with poor soil chemical quality. Humic substances can be used as fertilizer to increase macronutrient availability in the soil and improve pH. The application of coal ash can improve the soil’s chemical, physical, and biological properties because it has a pH value, high organic C content, available P, and basic cations such as K, Na, Ca, and Mg. This research aims to determine the effect and interaction of humic substances and bottom ash interaction with different doses to improve soil quality after a limestone quarry. This research uses a randomized block design in a factorial pattern. This experiment consisted of humic substances (H) with 4 levels H0, H1 (0.09%), H2 (0.12%), and H3 (0.15%), and bottom ash (B) with three levels: B0, B1 (400 grams), B2 (600 grams). Humic substances at H2 concentration (0.15%) significantly increased C-organic, K, P-available, Mg-dd, and increased plant height. In contrast, bottom ash treatment at a B2 (600 grams) dose significantly affected the increase in C-organic, P-available, and Mg-dd. The treatment of humic substances with concentrations of H3 (0.15%) and bottom ash at a dose of 600 grams is the best interaction characterized by an increase in soil pH, CEC, Ca-dd, K, and Na. The application of a concentration of H3 (0.15%) and the provision of a dose of B2 (600 grams) or 120 tons/ha significantly affect the chemical properties of post-mining soils limestone and increase plant height.