Produtividade de alface em função de diferentes espaçamentos e épocas de permanência do agrotêxtil.

Abstract

Although climatic conditions in the semiarid region of Paraiba are not the most suitable for lettuce crop, there are already cultivars and manage of plants that can be used in order to promote the growth and development of plants, thus increasing their production. The objective of this study was evaluate the lettuce yield as a function of different planting spacings and row cover in different seasons in Pombal - PB. The experimental design was a randomized complete block with squeme factorial 3 x 4, with three replications. These treatments came from the combination of three planting spacings (20 x 20, 25 x 25 and 30 x 30 cm) and four row cover times (0, 10, 20 and 30 days after transplanting - DAT). The experimental plots presented a total area of 0.8, 1.0 and 1.20 m2 with sixteen plants per plot, distributed in four rows, considering as useful to the four plants of the two central rows. During the execution of the experiment, the following variables were determined: plant height, shoot diameter, dry mass of stem, leaves and aereal part, number of leaves per plant, fresh mass of shoot and productivity. The fresh mass os lettuce was larger at 20 x 20 and 25 x 25 spacing only when the plant was covered by the row cover for 10 days. Regardless of the spacing tested, there was a reduction in fresh mass of shoot and productivity with the extension of the cover with row cover up to 30 DAT. The maximum yield obtained was 22.41 and 17.22 Kg.ha-1 at the row cover in the times of 4.8 and 12.3 DAT when the plants were grown at the planting spacings of 20 x 20 and 25 x 25 cm. In spite of the reduction of the 38.9% incident radiation provided by the row cover increase of the temperature inside the tunnel provided a lower accumulation of dry mass and lettuce productivity independent of the plant spacing.