Reclamation of Volcanic Deposits from Mt. Semeru using Vegetation and Indigenous Microbes: Measuring Vegetation Growth Rate and Carbon Increment

Abstract The eruption of Mount Semeru in East Java caused agroecosystems destruction. Volcanic deposits formed a crust that hindered plant root growth and decreased soil fertility. This study was an attempt to restore post-eruption land, using adaptive vegetation and indigenous microbes. Naphier grass (V1) was selected for its massive root system, ideal for penetrating compacted soil and improving soil structure. Centrosema sp (V2) and Indigofera sp (V3) were selected for their nitrogen-fixing abilities, which help replenish soil nutrients. These adaptive vegetations were combined with indigenous microbes ( Bacillus subtilis and Bacillus megaterium ), known for phosphor solubilization and nitrogen fixation to enhance reclamation efficiency. This study used a factorial randomized complete block design (RCBD) with two factors: vegetation types (V1, V2, V3) and microbial inputs (without microbes (M1) and with microbes (M2)). Vegetation was pruned every three months, and returned to the plot as organic matter input. Plant height, number of leaves, crop growth rate (CGR), relative growth rate (RGR), plants carbon content, and soil organic matter were measured. Data were analyzed using ANOVA to assess the statistical significance, followed by an LSD test at the 5% level to identify specific differences. Correlation and regression were performed to determine trends in each parameter. Naphier grass (V1) showed the highest CGR (67 g m −2 day −1 ) and highest plants carbon content (2,7 kg m −2 ) at 9 MAA, far surpassing Centrosema sp. (V2) and Indigofera sp. (V3). However, the highest soil organic matter content (1,15 %) found in Centrosema sp (V3) at 6 MAA. The application of indigenous microbes (M2) significantly improved all parameters. These findings highlight the potential of the adaptive vegetation with indigenous microbes to enhance land reclamation.