NITROGEN ACCUMULATION IN BIOMASS AND ITS PARTITIONING IN SUGARCANE GROWN IN THE BURDEKIN

THE COMMERCIAL SUGARCANE varieties Q253A, Q208A and KQ228A, which are grown in the Lower Burdekin, were sampled several times throughout the growing season to study the seasonal changes in nitrogen (N) content in the above- and below-ground biomass. In sugarcane approximately 130 days after planting (DAP), above-ground biomass contained up to 36% of the final above-ground biomass N content. By 200 DAP up to 84% of the total N content of the above-ground biomass had accumulated. From 200 to 270 DAP the rate of N accumulation slowed, and by 365 DAP the above-ground N content had plateaued in Q208A and KQ228A and decreased slightly in Q253A. Of the three varieties, Q253A appeared to accumulate N more rapidly than the other two varieties during the peak period of N accumulation. Nitrogen utilisation efficiency (kg of dry matter/kg crop N) of each of the three varieties was compared. KQ228A appeared to be more efficient than Q253A and Q208A. Below-ground biomass, which included roots and stool, of the variety Q208A was sampled at 200 and 365 DAP. At 200 DAP below-ground biomass N was 11% of the above-ground biomass N and by 365 DAP it was 15% of above-ground biomass N. The data presented in this paper provide an insight into the key periods of N uptake and its partitioning during sugarcane development under irrigation in the Lower Burdekin.