An improved way to determine nitrogen fertiliser requirements of sugarcane crops to meet global environmental challenges

• Published in: Plant and soil 2011-02, Vol.339 (1/2), p.51-67
• Main Authors: Thorburn, P. J., Biggs, J. S., Webster, A. J., Biggs, I. M.
• Format: Article
• Language: English
• Subjects: Agricultural industry; Agricultural site preparation; Biomass energy; Biomedical and Life Sciences; Cane sugar; Crop management; Crop production; Crop science; Crops; Ecology; Energy crops; Environmental impact; Fertilizer application; Fertilizers; Food processing industry; Industrial productivity; Life Sciences; Methods; Nitrogen; Nitrogen fertilizers; Plant Physiology; Plant Sciences; Regular Article; Soil Science & Conservation; Soil sciences; Sugar; Sugar cane; Sugarcane; Sustainable agriculture; Toy industry; Tropical environments
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-010-0406-2

Nitrogen (N) fertiliser management is increasingly important in sugarcane production as imperatives to reduce environmental impacts of N escalate. In this paper we report testing of a new concept for N management in sugarcane, the N Replacement system. This system relies on soil N cycling to 'buffer' differences in crop N needs and N fertiliser supply to individual crops, and aligns N applications with actual cane production over the longer-term rather than potential production. In 11 experiments, conducted in a wide range of environments over two to five crops, cane and sugar yields in the N Replacement treatment were similar to those achieved with the farmers' conventional N management, with a trend over successive crops for yields to increase relative to conventional management. At sites where experiments ran for at least 4 years, this trend resulted in cumulative sugar yields being higher in the N Replacement treatment. Average N applications were 35% lower in the N Replacement treatment, and N lost to the environment was estimated to be ~50% lower. Soil N 'buffering' was adequate to maintain sufficient N supply to crops even when yields were up to 30% greater than expected. Thus, it is not necessary to align fertiliser applications to potential sugarcane yields, which are rarely achieved in practice. Our results show that the ecologically-based N Replacement system has promise to deliver superior environmental outcomes without significantly reducing production of sugarcane, and potentially other semi-perennial crops, in the tropics and subtropics. Further evaluation of the system will be beneficial, and there is scope for determining more site-specific values of parameters in the system. However, care must be taken to evaluate the system over sufficient time frames (e.g. >2 crops) so that productivity improvement trends in the N Replacement system can be expressed.