Evaluation of substrate mixture in a lettuce yield (Lactuca sativa L.) var. Veronica

The production of vegetables on substrates has become a great alternative. Therefore, different substrates were evaluated in a greenhouse lettuce culture. A completely randomized block design (BCA) with three treatments was used as follows: T1: peat 30% coconut peat 70%, T2: peat 70% coconut peat 30% and T3: peat 50 % Coconut peat 50%, for a total of 9 experimental units each consisting of 10 plants. Every 8 days, during 32 days, the height of the plant, fresh and dry mass of leaves and root, leaf area and every 2 days, the SPAD units and the stomatal conductivity (SC) were determined. There were significant differences in the SPAD units in time for day 11 ddt with a value of 20.7. The SC presented the highest values in T3 and T2 with values of 354.2 and 366.2 mol m-2 s–1, respectively. T1 presented the highest value of stomatal resistance (RE) with 7.5 m2 s mol–1. The leaf area and height did not show significant differences. T2 at 15 days after transplant showed the highest values of fresh root mass (MFR), dry root mass (MSR) and fresh leaf mass (MFH) with 3.1 g, 0.106 g and 13.19 g respectively. In harvest, T3 showed 10% and 15% more production of MFH in lettuce than treatments T2 and T1, respectively.