The influence of planting times and silicon doses on the yield of crisphead lettuce

The influence of planting times and silicon levels were evaluated on yield and post-harvest quality of crisphead lettuce, cv. Raider. Two trials were carried out in Tres Pontas, Minas Gerais State, Brazil, from May to August of 2002 (winter season) and November to January of 2003 (summer season). A randomized complete block design of split-plots was used, with two planting times applied to the main plots (winter and summer season) and five silicon levels (0.0; 0.9; 1.8; 2.7 and 3.6 L ha(-1)) applied to the subplots in four replications. The highest total and commercial fresh mass and head circumference were obtained in the winter planting times. A quadratic model adjusted for silicon levels showed that 2.0 and 2.7 L ha(-1) levels resulted in the highest yield of total and commercial fresh mass, respectively. A maximum circumference of 40.1 cm was obtained with 2.1 L ha(-1) silicon, according to a quadratic model. The winter planting showed better post-harvest conservation than the summer planting when evaluated by a scale at 10 and 20 days after harvest. The application at 20 days after transplantation showed a quadratic effect where 2.0 L ha(-1) silicon level promoted the best post-harvest conservation of crisphead lettuce.