Crescimento, estado nutricional, produção e qualidade de infrutescências do abacaxizeiro ‘Pérola’ sob adubação nitrogenada e potássica

Abstract

The pineapple presents high nutritional demand, presenting the greater demand for nitrogen and potassium, nutrients that are related to the development of the culture and consequently the quality of the infructescence. Thus, in order to obtain high yields it is necessary to implement a program of careful fertilization, in which the contents of these elements must be adequately made available. For this purpose, the present essay was presented, which will be presented in two chapters. In the first chapter, the objective was to evaluate the mineral nutrition of the 'Pérola' pineapple under nitrogen and potassium fertilization. In the second, the objective was to evaluate the effect of vegetative growth, productivity and quality of infructescences of 'Pérola' pineapple under nitrogen and potassium fertilization. The experiment was conducted in the municipality of Alhandra, State of Paraíba, from January 2014 to March 2015. The experimental design was a randomized complete block, containing ten treatments and three replications, totaling 30 experimental units. The treatments were arranged according to the modified Plan Puebla III matrix, which consisted of the combination of N (30, 180, 300, 420, 570 kg ha-1) and K2O (30, 180, 300, 420, 570 kg ha -1). Puppy-like seedlings of the 'Pérola' cultivar were planted in a single rows system, at a spacing of 0.80 m x 0.30 m. The vegetative growth variables were determined at 150, 210, 270 and 300 days after planting (DAP), as well as the productivity and quality of the infructescences. Data were submitted to analysis of variance. In order to evaluate the effect of N and K2O doses and days after planting, the response surface and polynomial regression analysis technique was used, as well as analyzes of the main components of the aforementioned variables. In chapter I, 150, 210, 300, 420 and 300 days after planting were evaluated: the SPAD index, the chlorophyll content, and the N, P and K contents in leaf 'D' and in the soil. Between N and K2O, interaction was observed, with N and P content in the leaves linearly increased with time (days after planting), as well as soil P and K contents. For the SPAD index, there was a significant correlation with the levels of chlorophyll, potassium and nitrogen. Thus, it is evident that the SPAD index can be used to verify the nitrogen status in the 'Pérola' pineapple crop. In Chapter II, at 150, 210, 270 and 300 days after planting the following viii vegetative growth characteristics were evaluated: length, basal and median width, fresh and dry mass of 'D' leaf. The following variables were evaluated in the harvest at 15 months after planting: productivity, percentage of fruits of classes I (900 g to 1,200 kg); II (1,200 to 1,500 kg); III (1,500 to 1,800 kg) and IV (1,800 to 2,100 kg). In relation to post-harvest quality characteristics of infructescences, physical evaluations were performed: infructescence weight with and without crown, length of infructescence and crown, yield of crown, bark, stem and pulp of infructescences, and physical- chemical properties: titratable acidity (AT), soluble solids (SS), SS / AT ratio and ascorbic acid. Between the N and K2O rates, as well as the interaction of N doses with days after planting, there was an interaction, in which the increase of days after planting linearly increased the length, basal width and dry mass of leaf 'D'. For the leaf length 'D' there was a positive Pearson correlation with the fresh mass (r = 0.7465), basal width (r = 0.7906) and the median width (r = 0.6474). Productivity correlated positively with the fresh mass of crown infructescence (r = 1.00) and without crown (r = 0.7465), infructescence length (r = 0.6073) and mean fruit diameter r = 0.5725). The combination of the doses of 570 kg ha-1 of N and 570 kg ha-1 of K2O provided maximum increase in the basal width of 'D' leaf, while the highest dose of 570 kg ha-1 of N at 300 days after planting favored the fresh 'D' leaf mass. The application of the highest dose of N (570 kg ha-1) with the lowest dose of K2O (30 kg ha-1) produced infrutescences with the mass of 1,507.87 g and yield of 62.85 t ha-1.