Marginal land in Indonesia is about 24 millions which is dominated by dry land and most of it is Ultisols. This soil has the potential to be planted with sorghum which is drought tolerant. However, the low nutritional content of Ultisols requires fertilization to increase the productivity. The objective of this research was to evaluate the effect of fertilizers type and urea dose on plant growth and soil biology in sorghum cultivation for production of biomass energy in soil. This experiment used completely by randomized design with 25 combinations of soil treatment on two factors—the type of fertilizer consisting of compost (P1), compost plus inoculant (P2), slow-release fertilizer (P3), and the three combinations (P4); and different urea doses. The agronomic observation showed the highest values which were significantly different in the P4 treatment. This treatment also gave significant results on the total population of soil bacteria and fungi, and increased the C-organic content. However, the urea dose treatment did not give significant results which also there is no positive interaction with the type of fertilizer treatment. Increased production of sorghum biomass with higher soil fertility Ultisols was achieved when biofertilizers and a small amount of synthetic fertilizers were applied.