Adubação nitrogenada e potássica no cultivo irrigado de pitaia vermelha (Hylocereus sp.), sob condições tropicais

Abstract

The dragon fruit is an exotic fruit that is emerging in the national and international market. Due to its commercial attractiveness, profitability, precocity and rusticity, farmers have been investing and seeking to improve their cultivation. Several factors can affect fruit production and quality. Among them, the management of fertilization and plant nutrition, which is important to achieve satisfactory results. This study aimed to evaluate the effects of nitrogen and potassium fertilization on nutritional status, production and fruit quality of red dragon fruit (Hylocereus sp.) in irrigated crop. The experiment was conducted in a commercial farming area in Quixeré city, located in the Chapada do Apodi, state of Ceará. The experimental design was in randomized blocks, combining five nitrogen levels (30, 180, 330, 480 and 630 kg ha-1 of N) and five potassium levels (30, 180, 330, 480 and 630 kg ha-1 of K2O) with four repetitions. The source of N used was urea (45% N) and K the red potassium chloride (60% K2O). For fruit quality, a split plot was used, corresponding to the two evaluated periods (rainy and dry seasons). Basic fertilizers were made in the plots to provide phosphorus and micronutrients. Plant nutritional status, productive performance and fruit quality were evaluated. Potassium fertilization increased exchangeable K levels in the soil. The combinations of N and K at higher levels increased electrical conductivity of the soil solution. Higher nitrogen intake increased N, P, Zn and Mn levels in the cladodes. While potassium fertilization increased the K content. N doses affected the number of fruits only in the first growing season. The maximum yields in the first and second cycles were obtained with the doses of 383.9 and 332.2 kg ha-1 of N, respectively. Potassium fertilization did not affect productivity in the first cycle. However, at 362.2 kg ha-1 of K2O, higher yield was obtained in the second growing season. A first approximation for the range of N and K levels suitable for the dragon fruit was estimated between 9.7 and 9.9 g kg-1 and 26.3 and 29.4 g kg-1, respectively, in the cladodes. N fertilization affected the titratable acidity in the dry season. While SS/TA ratio was affected in both stations. Higher K intake affected titratable acidity and fruit pH during the dry season. N and K dose combinations influenced soluble solids and total and reducing sugars. The combination of 30 kg ha-1 of N and 30 kg ha-1 of K2O promoted higher values of these characteristics, except total sugars, which in combination 630 and 30 kg ha-1 of N and K2O, respectively, in the rainy season, promoted higher values. In general, nitrogen and potassium fertilization affected the productive performance and fruit quality. As well as affected soil fertility and nutrition of dragon fruit plant.