RENDIMENT O E TEORES DE MACRONUTRIENTES EM ALFACE TIPO AMERICANA EM FUNÇÃO DE DOSES DE NITROGÊNIO E MOLIBDÊNIO EM CULTIVO DE VERÃO Yield and content of macronutrients in crisphead lettuce (Lactuca sativa L.) in the summer planting as a function of nitrogen and molybdenum doses

This experiment was carried out in the town of Três Pontas, State of Minas Gerais, Brazil, from October to December, 2002, with the aim of evaluating the influence of nitrogen and molybdenum doses on the yield and contents of macronutrients in crisphead lettuce (Lactuca sativa L.). A complete randomized block design scheme with three replications was used, in which the treatments were a factorial combination of nitrogen doses in the top dressing additional to the 60 kg/ha N dose applied by the agriculturist (0.0, 60.0, 120.0, and 180.0 kg/ha) and five foliar molybdenum doses (0.0, 35.1, 70.2, 105.3, and 140.4 g/ha). The largest commercial fresh mass was obtained with the dose of 89.1 kg/ha nitrogen in the top dressing and 94.2 g/ha molybdenum. The results indicated an increase in the levels of N e P with increasing doses of nitrogen and molybdenum. The levels of potassium were reduced with the increase of the doses of nitrogen and molybdenum. Concerning the levels of Ca, Mg and S a significant effect from the interaction N x Mo was verified, which had their content increased in the plant tops with the increase of the doses of nitrogen and molybdenum.