To evaluate the decomposition rate and the C/N ratio of biomass residues from several crops that are the main food sources in Indonesia, a litterbag study was conducted from February to November 2016 on ultisols in Natar Village, South Lampung, Indonesia. There were four types of crops biomass residues used i.e., maize stovers, rice straws, shoots and leaves of cassava, and soybean stovers in the form of fresh or compost. A fifty gram dry weight of biomass was put into a litterbag, placed above the ground and at a depth of about 10-20 cm, and incubated for nine months. The remaining biomass (dry weight), the content of Organic-C, Total-N, and C/N levels of the remaining biomass in the litterbag were observed every month until nine months. The dry weight of biomass was obtained by an oven dried at 70°C for approximately 48 hours until reached the constant weight. The decomposition rates were measured as (k) = ln (X/Xo)/t. Results showed that the decomposition rate of the biomass residues of the four crops were different. The shoots and leaves of cassava biomass were most rapidly decomposed (k =-0.2830) and significantly different from others, followed by maize stover (k=-0.2066), rice straw (k = -0.1924), and soybean stover (k = -0.1675). Biomass of fresh or compost form and litterbag placement generally affected the decomposition rate of biomass residues.