Times of Application of Boron in Irrigated Rice Genotypes in Tropical Varzeas

Boron is an important micronutrient for all vegetables, being part of several metabolic functions within cells. Rice stands out as a staple food for more than half the world’s population and requires small amounts of boron. The objective of this study was to evaluate the effect of boron application at different times in the culture of irrigated rice in the conditions of the floodplains in the Southwest of the State of Tocantins. The experiment was installed at Fazenda Santa Rita, municipality of Lagoa da Confusao-TO in the 2015/2016 harvest, in bands, with a randomized block design, in a 4 x 4 factorial scheme, with 4 repetitions. The dose of 3.0 kg ha −1 of boron was applied, in the form of borax, via leaf, in four seasons. WereFour lowland rice cultivars (IRGA-424, IRGA-424 RI, IRGA-425, and IRGA-426) were used. The characteristics evaluated were: plant height, number of panicles, spikelet sterility, the mass of one hundred grains, grain yield, whole grains, and grain yield. Boron resulted in higher productivity. The highest yields were achieved with borate fertilization at 60 and 75 days after emergence. The genotypes IRGA-424 RI and IRGA-425 proved to be more efficient in the use of boron, is recommended at any time of application of the micronutrient.