Decomposition is a fundamental driver of biogeochemical cycling that dictates nutrient availability, carbon storage, and community composition. Although mechanistic models of decomposition dynamics have been successfully applied to many different systems, predicting decomposition in drylands has remained problematic due to a poor understanding of the driving variables. A recent study in the Sonoran Desert found a strong positive relationship between decomposition rates and the amount of soil deposited onto litter, which varied by a factor of six as a function of microsite vegetation cover. The mechanisms by which soil would enhance decomposition are not clearly understood. We established a controlled laboratory incubation study to test the influence of variation in the amount of soil-litter mixing and soil moisture levels on the rate of dryland litter decomposition. We hypothesized that a) soil deposition into litter enhances decomposition via enhancing microbial colonization and b) increased soil moisture enhances the rate of decomposition by accelerating microbial processes. The same mass of leaf litter (2 g) and soil (50 g) were incubated in sterilized 0.5 L glass jar microcosms, but microcosms differed in litter-soil mixing, soil moisture, and litter type. A three way randomized block design was used: three levels of soil-litter mixing (no soil coverage of litter, light soil coverage of litter, and complete mixing), three levels of volumetric soil moisture (2%, 6%, and 30%), and two different types of litter (mesquite and Lehmann lovegrass). To estimate the rate of litter decomposition, we harvested microcosms at 0, 1, 2, 3, 4, and 8 weeks after experiment initiation and analyzed the litter for mass loss, C content, and N content. Simultaneously, CO2 efflux from the microcosms was measured to estimate CO2 emissions from the litter decomposition and to compare litter mass loss and carbon loss via CO2. Soil-litter mixing is strongly a function of vegetation cover in dryland systems. Understanding the controls over decomposition in drylands is therefore a critical step toward increasing our understanding of how the dynamics of biogeochemical cycles are affected by vegetation change in drylands.