Resumo O objetivo deste trabalho foi determinar doses adequadas de nitrogênio para alcançar produtividade, qualidade das frutas e teor de nutrientes satisfatórios em cladódios de três espécies de pitaia. O delineamento experimental foi feito em blocos ao acaso, com arranjo fatorial 3×4. Os tratamentos consistiram das seguintes espécies de pitaia e doses de N: Selenicereus megalanthus, Hylocereus undatus e Hylocereus polyrhizus; e 0, 50, 100 e 200 g de N por planta, no primeiro ciclo de produção (safra 2016/2017) e 50, 100, 200 e 300 g de N por planta, no segundo e terceiro ciclos de produção (safras 2017/2018 e 2018/2019). A fertilização com N aumentou a produtividade, a qualidade das frutas e o teor de nutrientes nos cladódios das espécies. No terceiro ciclo de produção, a produtividade foi de 1,18 Mg ha-1 para S. megalanthus, 10,87 Mg ha-1 para H. undatus e 10,4 Mg ha-1 para H. polyrhizus em polinização aberta. A maior produtividade é obtida com 300 g de N por planta para S. megalanthus. Para H. polyrhizus e H. undatus, as doses são de 170 a 190 g de N por planta, complementadas com P e K.

Abstract The objective of this work was to determine adequate rates of nitrogen to reach satisfactory yield, fruit quality, and cladode nutrient content in three species of pitaya. The experimental design was carried out in randomized complete blocks, with a 3×4 factorial arrangement. The treatments consisted of the following pitaya species and N rates: Selenicereus megalanthus, Hylocereus undatus, and Hylocereus polyrhizus; and 0, 50, 100, and 200 g N per plant, in the first production cycle (2016/2017 crop season) and 50, 100, 200, and 300 g N per plant, in the second and third production cycles (2017/2018 and 2018/2019 crop seasons). Nitrogen fertilization increased the yield, fruit quality, and cladode nutrient content of the species. In the third production cycle, yield was 1.18 Mg ha-1 for S. megalanthus, 10.87 Mg ha-1 for H. undatus, and 10.4 Mg ha-1 for H. polyrhizus in open pollination. The highest yield is obtained with 300 g N per plant for S. megalanthus. For H. polyrhizus and H. undatus the rates are from 170 to 190 g N per plant, supplemented with P and K.

ABSTRACT. Pitaya species cultivation in Brazil is recent, and information on the production of the species Selenicereus megalanthus, known as yellow pitaya, is non-existent because research in the country has focused on the species Hylocereus undatus. The research was carried out with the objective of evaluating the reproductive phenology of the species S. megalanthus, in a high-altitude climate conditions in Brazil. The study orchard of yellow pitaya was located at an altitude of 726 metres, 18º 04' 15" S latitude and 43º 28' 15" W longitude, and has an Aw climate, classified as high-altitude tropical. Phenological evaluations were carried out through visual observations, from the beginning of floral button formation until the end of the fruit harvest, during three production cycles. On each plant, flower buds were marked to determine the time from floral button formation until flower anthesis and from flower fertilisation until fruit ripening. The period of flowering and harvesting of the yellow pitaya was determined according to the phenological stage records. Flowering began in the spring, with successive flowering events until the autumn. The time between floral button formation until anthesis ranged from 46 to 55 days. The time from flower fertilisation until fruit ripening ranged from 96 to 110 days. Fruit harvest began in the summer and ended in winter. The reproductive cycle of S. megalanthus is longer than H. undatus and H. polyrhizus, which are also cultivated in Brazil, ranging from 147 to 166 days from floral button formation to fruit harvest.

RESUMO. A pitaia é uma frutífera que está se tornando promissora no mundo, devido a qualidade de seus frutos, no que tange o sabor e formato externo peculiar. Por ser uma espécie de cultivo recente, informações sobre fertilização são essenciais para permitir sistemas de produção. Nesse sentido, a pesquisa foi realizada com o objetivo de estudar diferentes doses de K2O para o cultivo de pitaia. As espécies Hylocereus undantus e Hylocereus polyrhizus foram estudadas em condições de campo. As pitaias foram cultivadas no espaçamento de 3 x 3 m e quatro doses de K2O foram testadas: 0, 50, 100 e 200 g de planta-1, com esquema fatorial 2 x 4, distribuídos em delineamento em blocos casualizados. A produção por planta (kg e número de frutos) foi avaliada nos ciclos de produção 2013/2014, 2014/2015 e 2015/2016. Também avaliou-se a qualidade das frutas: diâmetro longitudinal, diâmetro transversal, massa, teor de sólidos solúveis, acidez titulável e ratio. A adubação com potássio aumentou a produção e proporcionou melhor qualidade das frutas de pitaia. A adubação com K2O deve ser de 106,0 a 133,3 g K2O no primeiro ano e 200 g K2O no segundo e terceiro ano após o plantio.

ABSTRACT. Pitaya is a fruit that is becoming promising for cultivation around the world due to the quality of its fruits in terms of taste and their peculiar external shape. Because it is a recenttly cultivated crop, information about fertilization is essential to enable its production. In this sense, this study was performed aiming to evaluate different doses of K2O for pitaya cultivation. Hylocereus undatus and Hylocereus polyrhizus were studied under field conditions. Pitayas were cultivated at a 3 × 3m spacing, and four doses of K2O were tested: 0, 50, 100, and 200 g plant-1, with a 2 × 4 factorial arrangement distributed in a randomized block design. The production per plant (kg and number of fruits) was evaluated in the production cycles of 2013/2014, 2014/2015, and 2015/2016. The fruit quality was also evaluated: longitudinal diameter, transverse diameter, mass, soluble solids content, titratable acidity and soluble solids/titratable acidity ratio. Potassium fertilization increased production and provided a better quality of pitaya fruits.K2O fertilization should be from 106.0 to 133.3 g K2O in the first year and 200 g K2O in the second and third years after planting.