The choice of crops in rotation influences the size of effect on SOC. Integration of crops with less intensive rooting systems and lower residue input to the soil can lead to a reduction of SOC. For example, crop residues may be removed for animal fodder. Also integration of many crops with a low carbon to nitrogen ratio can lead to SOC depletion because these plant residues decompose more quickly due to higher nitrogen content. As for all SOC solutions, pedoclimatic conditions and soil management practices influence the carbon dynamics in the soil.

How much actual SOC gain can be generated by the introduction of grass leys depend on several factors, such as the ley duration, species composition, climate, soil type and management practice (e.g. cutting vs. grazing, or fertilization management). When the ley is terminated and tillage resumes, some of the accumulated carbon can also be lost. Because these variables interact differently in each system, SOC sequestration rates vary widely between rotations that include grass leys. Regarding GHG emissions, the integration of grass-clover leys helps to increase nitrogen input into the crop rotation and thus mineral fertilizer application can be reduced.