In order to study the behavior of three lettuce cultivars (Júlia, Tainá e Grandes Lagos) in four doses of filter cake (0; 10; 20 and 40 ton ha-1), in greenhouses (tunnel) was conducted an experiment at the Universidade do Estado de Mato Grosso, an area with Oxisol (clay) in the months from March to May 2009. The experimental design was randomized blocks arranged in a 3x4 factorial (cultivars x dose) with four replications. We evaluated the following agronomic characteristics: circumference of the plant (CP), total fresh mass (TFM), fresh commercial mass (FCoM), head fresh weight (HFW), stem diameter (SD), number of marketable leaves (NML), stem length (SL) and total number of leaves (TNL). The cultivars Júlia and Tainá responded to fertilization with filter cake until the dose of 40 ton-1. The cultivar Grandes Lagos responded to fertilization with filter cake until the dose of 35 t ha-1 for TFM and HFW and up to 40 ton ha-1 for FCoM. The cultivar Grandes Lagos had the best performance in TFM, FCoM, CP and SL compared to others cultivars, and equated with the cultivar Tainá in HFW and NML and with the cultivar Julia in SD. All cultivars had similar behavior in TNL. The organic fertilization with filter cake increases the productivity of cultivars of lettuce.
