Due to the increasing national and international demand, the cultivation of açaí palm trees (Euterpe oleracea Mart.) has expanded to upland areas in Brazil. Most of these areas present low natural soil fertility, in which boron (B) is one of the most limiting nutrients. This study aimed to evaluate the productivity of fresh fruits of fertigated açaí trees submitted to doses of B. The study was carried out in Tomé-Açu, northeastern Pará, Brazil. The experimental design consisted of randomized blocks with four treatments: control and addition of 20, 40 and 60 g of B clump-1. After 17 months, bunches of fresh fruits were collected and the production per hectare was estimated. An economic analysis was carried out considering the costs of fertilization and fruit production. The productivities obtained in the treatments were considered above the average of the municipality of Tomé-Açu. The estimated content of leaf B that provided the highest productivity was 14.9 mg kg-1, for a yield of 5479 kg ha-1 year-1¸ while the critical content corresponded to 13.2 mg kg-1. The highest productivity of fresh açaí fruits was achieved with the dose of 20 g of B clump-1, which provided a net gain of 42%.

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This study aimed to define management zones (MZs) for fertirrigated açaí cultivation, based on spatial variability of the foliar nutrients and productivity data. The work was carried out in an area of 5.75 ha of a 7-year crop, with 80 georeferenced sample points. Fresh fruit productivity and nutrient (N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, and Zn) contents were determined. The average contents of macronutrients were considered adequate for adult açaí plants, and their spatial dependence associated with fruit productivity allowed the representation of their distributions through maps of variability. Through multivariate analysis, three main components were highlighted. These components explained 51.5 % of the total variability of the data, where PC1 showed a higher correlation with Ca, Mg, K, and P. In addition, three MZs were obtained, out of which one with the highest productivity showed the best Ca, Mg, S, B, and Fe leaf contents. Principal component analysis and determination of MZs emphasized Ca and Mg nutrition as being more related to spatial variability and açaí fruit productivity.

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