Interpretation of a simple nitrogen use efficiency index for informing nitrogen fertiliser management in the Burdekin

OPTIMISING NITROGEN USE efficiency in the Queensland sugar industry will provide profitability (grower focus), productivity (industry focus) and environmental (social license focus) benefits by ensuring that the crop recovers the maximum amount of applied nitrogen (N), thereby minimising off-site N movement. A simple indicator of N use efficiency is the tonnes cane produced per kg applied N (Partial Factor Productivity of N or Apparent Fertiliser N-use Efficiency- AppNUEFert). Data were used from N-responsive sites/seasons in the RP20 Burdekin nitrogen trials (replicated strip trials) to develop interpretation guidelines for AppNUEFert in the Burdekin Delta and Burdekin River Irrigation Area. Case studies of partial N budgets illustrated how AppNUEFert was affected by both applied N recovery by the crop (dependent on the magnitude of N losses) and also by the ability of the crop to convert in-crop N to yield (determined by soil constraints, management practices and seasonal conditions). Particular attention is paid to AppNUEFert interpretation for low yielding sites and inferences that can be drawn from AppNUEFert for the management of these sites.