Residue retention and reduced tillage are both conservation agricultural management options that may enhance soil organic carbon (SOC) stabilization in tropical soils. Therefore, we evaluated the effects of long-term tillage and residue management on SOC dynamics in a Chromic Luvisol and Areni-Gleyic Luvisol in Zimbabwe. At the time of sampling the soils had been under conventional tillage (CT), mulch ripping (MR), clean ripping (CR) and tied ridging (TR) for nine years. Soil was fully dispersed and separated into 212-2000 µm (coarse sand), 53-212 µm (fine sand), 20-53 µm (coarse silt), 5-20 µm (fine silt) and 0-5 µm (clay) size fractions. The whole soil and size fractions were analyzed for C content. Conventional tillage had the least amount of SOC, with 14.9 mg C g-1 soil and 4.2 mg C g-1 soil for the red clay and sandy soils, respectively. The highest SOC content was 6.8 mg C g-1 soil in the sandy soil under MR, whereas for the red clay soil, TR had the highest SOC content of 20.4 mg C g-1 soil. The coarse sand-size fraction was most responsive to management in the sandy soil where MR had 42% more organic C than CR, suggesting that SOC contents of this fraction are predominantly controlled by amounts of C input. In contrast, the fine sand fraction was the most responsive fraction in the red clay soil with a 66% greater C content in the TR than CT. This result suggests that tillage disturbance is the dominant factor reducing C stabilization in a clayey soil, probably by reducing C stabilization within microaggregates. In conclusion, developing viable conservation agriculture practices to optimize SOC contents and long-term agroecosystem sustainability should prioritize the maintenance of C inputs to coarse textured soils, but should focus on the reduction of SOC decomposition in fine textured soils.