Soil microbial activity is strongly influenced by agricultural management and the quality of plant residues added to the system. Basal soil respiration is an important biological indicator, as it expresses the CO₂ emissions resulting from the decomposition of organic matter by microorganisms. In this context, the present study aimed to evaluate basal soil respiration under different types of service plant mulch. The experiment was conducted in the laboratory at the State University of Rio Grande do Sul (UERGS), in the municipality of Cachoeira do Sul, using soil with previously determined gravimetric moisture content. The treatments consisted of a control, forage turnip mulch, black oats, and ryegrass, with two replicates each. CO₂ emissions were evaluated through weekly titrations over four weeks. The results showed that forage turnip mulch had higher cumulative CO₂ emissions, indicating faster decomposition, associated with its lower C/N ratio and greater availability of labile compounds. Black oats had a lower respiration rate, attributed to higher lignin content and slower decomposition, while ryegrass showed intermediate behavior. It is concluded that the chemical quality of plant residues has a decisive influence on soil basal respiration and should be considered when choosing service plants for more sustainable agricultural systems with greater carbon retention potential.