The sowing system, as well as the species used as covercrops, may interfere with the production of straw and the development of further crops. The objective of this research was to evaluate sowing systems for black oat (Avena strigosaSchreb) and white lupine (Lupinus albus) as cover crops, the dry matter production of these plants and their influence on Americana and Curly lettuces yield. Two experiments were performed, one for each lettuce cultivar. The experimental design was composed of 8 treatments (factorial 4x2), evaluated in randomized blocks, with five replications. The first factor is related to four soil coverages (black oat, white lupine, black oat + white lupine and weed) and the second one is the sowing system (handand mechanized in line). The cover plants drying was performed 47 days after planting and the amount of dry matter produced in the area (straw) was then measured. After 30 days from drying, varieties of Curly and Americana lettuce were planted under straw. The lettuce cultivars were evaluated for fresh mass, shoot height and head diameter. For both lettuces, the benefit ofgreen manure was higher using black oat only or combinedwith white lupine, either handor mechanized sowed.