Effect of temporal nitrogen-management strategies on sugarcane production in sub-tropical Queensland – a complete crop cycle

Although the nitrogen (N) guidelines within the SIX EASY STEPS program are robust and applicable for most soils and circumstances, opportunities exist for fine-tuning the N application rates using temporal management strategies. These include split applications and use of enhanced-efficiency fertilisers (EEFs). This paper reports on the overall outcomes of a temporal-N trial conducted over a crop-cycle in southern region of the Australian sugar industry. Reports have indicated that EEFs have the best chance of contributing to improved productivity, profitability and NUE in sugarcane, when soils are subject to extended wet periods. Although the trial described here was located on an usually well-drained site, different seasonal climatic conditions enabled assessments under different conditions. Sugarcane yield responses to the different temporal-N strategies compared to the use of standard urea applied as single applications each season were essentially absent across the crop cycle on this relatively high-fertility-status soil. However, no single temporal N strategy was superior to the others. Mean partial net return (PNR) values for the crop cycle showed that the best return on applied N was associated with a standard urea applied at a rate of 120 kg N/ha in a single application in each season (standard treatment). Losses in mean partial net returns ($/ha/year) of each treatment relative to the standard treatment showed that similar mean PNR values resulted from standard urea applied at 160 kg N/ha and DMPP-urea applied at both rates (120 and 160 kg N/ha). Split applications of urea generally resulted in lower PNRs compared to the standard treatment. Application of PC-urea (both rates) was the least profitable at the trial site. Further results from EEF evaluations being undertaken by others may shed light on the advantages of temporal management strategies on sugarcane production on soils that are normally found in imperfectly drained conditions in bottomland positions. Key words Sugarcane, temporal nitrogen management, split applications, enhanced-efficiency fertilisers