Magnesium fertilization, broth quality and sugar production by cane varieties RB867515 and RB92579

The nutritional status, juice quality and sugar production of sugarcane varieties RB867515 and RB92579 were evaluated in the cane-plant cycle, as a function of magnesium doses applied at the bottom of the planting furrow. The study, installed in soil with a Mg content equal to 0.61 cmolc dm-3, was conducted in an experimental design in randomized blocks with four replications. The study was a 2 x 5 factorial: two sugarcane varieties: RB867515 and RB92579, and five doses of magnesium: zero, 60, 120, 180 and 240 kg per hectare, using magnesium oxide as a source of Mg. commercial magnesium. The plots consisted of seven furrows of five meters in length with 1.0 meter spacing. All plots received phosphorus and potassium fertilization at a dose of 100 kg of phosphorus and 150 kg of potassium per hectare, with no nitrogen fertilization. In the maximum growth phase of sugarcane, the nutritional status of sugarcane was evaluated. About a year after planting, when the cane was mature, the cane plant was harvested to assess the quality of the juice and the sugar production of the varieties. There was no effect of magnesium fertilization on any of the analyzed variables. Regarding the nutrient content in leaf +3, nutritional deficiency was found only for potassium, copper and manganese. The RB92579 had an average productivity of industrializable stalks and sugars, respectively of 96.0 and 13.7 tons per hectare, surpassing the RB867515 by about 10%. The results of this study confirm reports by other researchers who mention that Mg contents of the order of 0.50 cmolc dm-3 are sufficient for adequate nutrition of sugarcane.