Calcium Nitrate Dose and Application Period in American Lettuce (Lactuca sativa L.)

The aim of this study was to evaluate the yield of American lettuce subjected to different dosages of calcium nitrate on two application schedules. The experiment used four replicates of a 2 × 5 factorial randomized complete block design, with two application schedules (Schedule 1: 50% of the dose at transplanting and 50% at 20 days after transplanting; Schedule 2: 50% at 10 days and 50% at 20 days after transplanting) and five doses (0, 150, 300, 450 and 600 kg ha-1). The following variables were evaluated: the number of inner and outer leaves, head height and diameter, head height/diameter ratio, compactness, stem diameter, relative index of chlorophyll, commercial production and nitrogen (N) and calcium (Ca) content in the inner and outer leaf. The data were subjected to analysis of variance (F test, with Tukey test for comparison of the means) for the application schedule and regression analysis for the calcium nitrate dose. The application of calcium nitrate positively influenced the nutritional characteristics of American lettuce in the 2nd schedule and the dose of 470 kg ha-1 presented better production.