Combinations among cultivars, environments and soil tillage capable of improving the agronomic performance and to increase the yield of lettuce under organic cultivation were studied. The research was carried out in Rio Branco, Acre State, using the experimental design of randomized blocks with four replicates, in split-plot arrangement. In each experiment (field and greenhouse), three lettuce cultivars (Simpson, Marisa and Vera), constituting the split-plot, were raffled in the plot represented by four soil tillage and mulching treatments (conventional tillage using mulch of rice husk, silvered polyethylene, unmulched soil and no-tillage). The commercial yield of lettuce was of 12.3 t ha-1 in greenhouse and of 7.9 t ha-1 in field. The cultivation in greenhouse improved the development of the plants, characterized by higher fresh and dry matter mass of shoots, commercial fresh matter mass and better commercial classification, besides good agronomic performance and high yield with any of the mulching. The cultivars Simpson and Marisa presented the same dry matter mass of shoots and were superior to 'Vera'. However, cultivar Simpson presented elevated stem growth characterizing precocious flowering, reducing the commercial quality. Cultivars Marisa and Vera with reduced stem prolongation are tolerant to the environmental conditions of Rio Branco. Mulching the soil with rice husk or silver plastic in field contributed to minimize the harmful climatic effect to the cultivation of lettuce. The organic no-tillage cultivation did not differ from that one in unmulched soil.
Lactuca sativa L; no-tillage; organic agriculture
