Rice Straw Compost and Husk Biochar as Growth Starters and In Vitro Heavy Metal Biosorbents

Abstract

Soil microbial activity is known to increase with compost application, aiding in nutrient absorption by plants and the provision of growth-promoting chemicals. Biocar, derived from plant fires or through heavy metal biosorption, also plays a crucial role in soil improvement. Therefore, this study aimed to develop rice straw compost and husk biochar as growth starters and evaluate their potential for heavy metal biosorption in vitro. The experiment was conducted in Samarinda, East Kalimantan, Indonesia, from October 2023 to January 2024. Rice straw and husk were collected at several random points in previously determined active fields (Stage I Point 4). After characterizing the chemical and physical properties, the rice straw was composted, and the husk was biocharized. The incubation medium used was rice field soil from Samarinda, while straw compost, husk biochar, soil compounds, and heavy metals were evaluated at the Soil Science Laboratory, Mulawarman University. In addition, microbial analyses were performed at the Plant Pest and Disease Laboratory, Faculty of Agriculture, and Microbiology Laboratory, Faculty of Fisheries and Marine Sciences. The results showed that compost materials and biochar content strongly influenced the overall bacterial and fungal colonies. As the incubation time increased, the bacterial and fungal colonies decreased. During the initial two months of waste intake, the number of colonies significantly increased, showing a notable difference compared to periods before the addition of compost or biochar.