Cultivares de alface crespa roxa em diferentes épocas e ambientes de cultivo em Iranduba, AM

Abstract

Lettuce (Lactuca sativa L.) is the main leaf vegetable consumed in Brazil and the third vegetable in production volume, which justifies it's significant economic importance. Because of the development of summer cultivars, new crop treatments, and the increase of protected crops, lettuce can now be found all over the country, produced all year round by small, medium and large producers. However, several environmental factors affect the growth and development of lettuce in the Amazon region, which makes cultivar tests necessary in order to adapt the crop to different regions. Due to the lack of information on the adaptation of purple lettuce cultivars to the climatic conditions of the State of Amazonas, this work aimed to evaluate the performance of purple lettuce cultivars under different seasons and cropping systems at Iranduba, AM. Four experiments were performed at Iranduba, AM, from July 2016 to January 2017, two in the dry season and two in the rainy season. The cropping systems tested were: 1 - open field and 2 – protected cropping (greenhouse). The area used for the open-field experiment showed flat topography, with no physical or chemical barriers against vegetable crops. The greenhouse used was made of a 30 m long, 8 m wide, 2.5 m height wooden structure covered with a 150 micras transparent plastic. The experiment was design in randomized blocks with four replicates, and the treatments featured 11 purple lettuce cultivars: Lavine (Feltrin®), Mirella (Feltrin®), Rubinela (Feltrin®), Scarlet (Sakata®), Rosabella (Tecnoseed®), Pira Roxa (Tecnoseed®), Belíssima (Tecnoseed®), Red Star (Topseed®), Banchu Red Fire (Takii Seed®), Vermelha Rouge (Sakama®) and Rubia (Horticeres®). The cultivars were evaluated in terms of fresh mass of the aerial part, leaf dry mass, plant height, number of commercial leaves, stem length, and diameter of the aerial part. At the open field, none of the evaluated cultivars were able to develop in the rainy season, while in the dry season the cultivars that had the highest fresh mass of aerial part and dry mass of leaves were: Banchu Red Fire, Rosabella and Scarlet. At the greenhouse, the Banchu Red Fire, Rosabella, and Scarlet cultivars showed the highest rates for fresh mass of aerial part and dry leaf mass. Their dry leaf mass was larger in the rainy season than in the dry season. The Lavine cultivar showed the highest stem length and plant height under both cropping systems, and was higher in the dry season than in the rainy season. The comparison between the cropping systems in the dry season showed that purple lettuce crops under open-field conditions yield less than under protected cropping. The conclusion is that the Banchu Red Fire, Rosabella, and Scarlet cultivars showed the best growth parameters at the greenhouse during both seasons, and at the open field during the dry season, which makes them the most adequate choice for crops at the study region.