Adubação com potássio e boro sobre a produtividade, qualidade do fruto e teor de prolina em laranjeira 'Pêra'

Abstract

The objective of this study was to evaluate the productivity and quality of citrus fruits due to the fertilization with K and B in an orchard in production. The experiment was conducted in Rio Preto da Eva-AM. The experimental design was a randomized block with four replications, the treatments were arranged in a factorial arrangement (4 x 3 + 1), involving four levels of K (60, 120, 240 and 360 g plant-1 of K2O) and four levels of B (4, 8, 16 and 24 g plant-1 B) plus control portion (not K and B) a total of 17 combinations. It was used as source of K potassium chloride, and borax as a source of B. The evaluated range was “Pera” seven years of cultivation, a spacing of 7 x 2,5 m. Soil samples were collected at 0-20 and 20-40 cm, leaves and fruit in the years 2014 and 2015. Through the F test (P ≤ 0,05) contrast the significance was obtained by comparing the average factorial arrangement with the control treatment. From equations adjusted for productivity as a function of doses were estimated corresponding doses for maximum physical efficiency (MEF) and maximum economic efficiency (MEE). The critical level of K and B in soil and plants were estimated by substituting the dose to MEE in the equations that relate the K and B concentrations with the contents available in the soil and with the contents in leaves, respectively. Considering the media of the two years of study it can be concluded that: Doses 300: 16 g plant-1 of K2O and B promoted greater K and B content in the layer 0-20 cm from the ground; The K, Mg and B were affected by the addition of K2O and B, whereas P and Mn nutrients were only affected by the addition of B, Cu for K2O; Doses 244: 20 g plant-1 K2O and B were those that showed higher contents of K and B, respectively, on the sheet; Doses 304: 21 g plant-1 of K2O and B were those that provided lower free proline content in the leaves; Doses 311: 21 and 316: 18 g plant-1 of K2O and B provided respectively, the best physical and chemical characteristics and higher technological content of the fruit; The maximum physical efficiency and maximum economic efficiency were 277: 23 and 222: 22 g plant-1 of K2O and B, the maximum economic efficiency recommended for fertilization of orchards in production and the critical levels in the soil were 40 and 0,20 mg dm-3 available K and B, respectively, and the sheet 17 g kg-1 K and 217 mg kg-1 B.