With the objective of evaluating the influence of doses of zinc sulphate on yield and quality of iceberg lettuce (Lactuca sativa L.), three distinct trials were carried out at Três Pontas, State of Minas Gerais, Brazil, from May to June of 2002. The experimental design was randomized blocks with five doses of zinc sulphate (0, 0.9, 1.8, 2.7 and 3.6 kg ha-1), applied to the foliage at three different application times (14, 21 and 28 days after transplanting), and four replicates. The characteristics total and commercial fresh mass (g plant-1), commercial head circumference (cm) and stem length of commercial head (cm) were evaluated. The total and commercial fresh mass characteristics evidenced independent significative effects to the doses of zinc sulphate and application times. For total fresh mass, the dose of 2.01 kg ha-1 of zinc sulphate was estimated to present the highest yield. In relation to application time, this characteristic was estimated to present the highest yield (988 g plant-1) when the pulverization was realized at 14 days. The dose of 2.09 kg ha-1 was estimated to achieve the highest yield for commercial fresh mass, the application at 14 days being statistically superior, with a yield of 593 g plant-1. For head circumference, the dose of 2.63 kg ha-1 of zinc sulphate was estimated to bring showed the highest return. No significant effects were observed for stem length.
Lactuca sativa L.; plant nutrition; micronutrient
