Nitrogen and molybdenum rates on the yield and macronutrients content in crisphead lettuce

Nitrogen and molybdenum rates on the yield and macronutrients content in crisphead lettuce The trial was carried out at Tres Pontas, Minas Gerais state, Brazil, from April to July 2003, to evaluate the influence of nitrogen and molybdenum rates on yield and macronutrients uptake of crisphead lettuce. A randomized complete blocks design with three replications was used. The treatments consisted of a factorial combination of four top dressing nitrogen levels (0.0; 60.0; 120.0 and 180.0 kg ha(-1)) and five foliar molybdenum levels (0.0, 35.1; 70.2; 105.3 and 140.4 g ha(-1)). The marketable fresh mass showed significant effect for levels of nitrogen and of molybdenum, as well as for their interaction, while the content of nitrogen and magnesium acted independently. The levels of potassium were reduced with the increase of the doses of nitrogen and molybdenum, and for the highest level of molybdenum (140.4 g ha(-1)) occurred a quadratic effect in which the dose of 76.1 kg ha(-1) of N in top dressing showed the highest level of potassium. For the content of P, Ca and S a significant effect from the interaction N x K was verified, which had their content increased in the plant tops with the levels of nitrogen and molybdenum.