Abstract

Boron (B) is important for the nutrition and development of sunflower crops because of the damage that its deficiency can cause in plants, compromising the final crop productivity. This work aimed to evaluate the application of B doses at different phenological stages of the sunflower crop. The project was conducted in the experimental area of the Goiás State University, Campus of Ipameri, located in Ipameri-GO, in a randomized block design, arranged in a 2 x 5 x 6 factorial scheme, with four replications. The factors consisted of crop seasons (2017 and 2018), application at different phenological stages (V0, V6, V18, R1, and R3), and B doses (0, 1, 2, 3, 4, and 5 kg ha^-1), respectively. In each crop season, leaf boron content, relative chlorophyll index, plant height, stem diameter, capitulum diameter, capitulum mass, number of achenes per capitulum, 1000-achene weight, and achene yield were assessed. The use of doses between 3.38 and 3.74 Kg ha^-1 of B influenced the characteristics of leaf boron content, plant height, and 1000-achene weight. Most of the parameters assessed, including crop yield, were influenced by crop seasons due to rainfall distribution during the crop cycle. The 2017 off-season had the best results.

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