Biochar application in Calliandra calothyrsus plantation management

Calliandra ( Calliandra calothyrsus ) is a woody shrub with various characteristics that have made it useful in agroforestry systems. Recently, a biomass gasification power plant (BGPP) is engaging in extending calliandra plantations because of calliandra’s high heating value. Since the byproduct of BGPP is biochar, widely known for helping CO 2 mitigation, this research aims to integrate biochar application into calliandra plantings. Experiments evaluating biochar applications were implemented on a new farm in Indonesia's Kundur Island, yielding calliandra wood for BGPP and fresh leaves for sheep farming. Chicken manure that had been co-composted with biochar was provided as fertilizer. In nursery experiments, the application of 1.1 kg m −2 biochar provided the greatest qualified seedlings. A field experiment showed that 1 or 1.25 kg m −2 biochar application yielded the most sizable wood and fresh leaves. The soil covering with biochar increased the yield of wood and fresh leaves, suggesting biochar mulching could be used for subsequent batches of calliandra regeneration. Thus, this study concluded that the application of biochar benefited calliandra nursery planting, field planting, and shoot regeneration. With a stable monthly temperature, the experiment site could have insufficient calliandra growth due to distinct dry and wet seasons. The regression analysis showed a strong correlation (R 2 > 0.878) between wood production and rainfall, suggesting the growth of calliandra could be predicted from rainfall forecasts. Therefore, a calliandra agroforest system with biochar application and sufficient rainfall could enable a sustainable biomass supply for both BGPP and sheep farming.