Sugarcane is used
worldwide for sugar, ethanol and energy production. In Brazil, the shift from
burned to unburned harvest systems resulted in increases in nitrogen
fertilization rates, which can impact root architecture and biomass. The
expectation is also an increase in sugarcane biomass. The study hypothesized
that high N rates applied to sugarcane fields increases root growth and N
stored in roots, promoting higher biomass and N accumulated in shoots. Two
experiments were set up in Southeastern Brazil, on a Typic Kandiudox (TK) and
Rhodic Eutrudox (RE). Four treatments were studied
1) N application in the plant-cane (0 and 120 kg·ha
-1 N) and 2) N application in the ratoon (0 and 150 kg·ha
-1 N). The
shoot biomass and the root density (by the core method up to 0.6 m) were
evaluated over the first ratoon crop cycle, and the N content in those compartments
was also examined. There was no carry over effect on N applied at planting in
root and shoot biomass in the ratoon crop cycle. At the RE site, the ratoon N
fertilization increased root density in the superficial soil layer (0 - 0.2 m)
and close to the plants (<0.3 m). The effect of N addition on root biomass,
and biomass and N accumulated in shoot was limited in both sites. Increasing N
rates in unburned sugarcane fields do not consistently increases root and shoot
biomass under Brazilian field conditions.