Improving sugarcane nitrogen management in the Wet Tropics using seasonal climate forecasting

Skocaj, Danielle Maree (2015) Improving sugarcane nitrogen management in the Wet Tropics using seasonal climate forecasting. PhD thesis, James Cook University.

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Abstract

The Wet Tropics sugar industry experiences one of the highest levels of inter-annual climate variability in the world. This has a significant impact on cane yields and nitrogen losses and makes the task of applying the right amount of nitrogen fertiliser to optimise profitability and minimise environmental losses extremely challenging. Improvements in fertiliser nitrogen use efficiency will be required to ensure the economic and environmental sustainability of the Wet Tropics sugar industry.

The size of the crop (cane yield) largely determines how much nitrogen fertiliser should be applied. Spring-summer rainfall was found to have a strong influence on Tully cane yields. Nitrogen fertiliser requirements in dry (i.e. low spring-summer rainfall) and wet (i.e. high spring-summer rainfall) years for ratoon sugarcane crops grown on the Bulgun series soil were investigated in a simulation study. As the majority of nitrogen fertiliser is typically applied to ratoon sugarcane crops during spring, seasonal climate forecasting indices based on sea surface temperature anomalies in the central equatorial Pacific Ocean were also investigated for their utility to predict nitrogen fertiliser requirements with sufficient lead-time.

The simulation study identified nitrogen fertiliser requirements are on average, 25% lower in wet years, defined as the June to August Oceanic Niño Index being in the La Niña phase, for ratoon sugarcane crops grown on the Bulgun series soil. The June to August Oceanic Niño Index can be used to predict nitrogen fertiliser requirements for ratoon sugarcane crops grown on the Bulgun series soil. Sugarcane growers should consider reducing nitrogen fertiliser application rates to ratoon sugarcane crops grown on the Bulgun series soil when the June to August Oceanic Niño Index is in the La Niña phase. This is because the chance of experiencing high spring-summer rainfall at Tully increases when the June to August Oceanic Niño Index is in the La Niña phase.

Given that high spring-summer rainfall is associated with lower cane yields, reducing nitrogen fertiliser rates in wet years will improve fertiliser nitrogen use efficiency. Reducing nitrogen fertiliser rates below the SIX EASY STEPS nitrogen guidelines to sugarcane ratoon crops grown on the Bulgun series soil, every year, will also improve fertiliser nitrogen use efficiency. Despite delivering an environmental benefit, reducing nitrogen fertiliser rates every year will reduce productivity and profitability. Future research should focus on understanding the full economic, environmental and social benefits of these strategies.

Older ratoons were found to recover less nitrogen in total, than younger ratoons, but were more reliant on fertiliser nitrogen. This indicates nitrogen fertiliser guidelines should be reviewed for ratoon sugarcane crops grown on the Bulgun series soil. The current SIX EASY STEPS nitrogen management guidelines do not differentiate nitrogen fertiliser requirements between ratoon sugarcane crops. More research is required to quantify the nitrogen recovery of successive ratoon sugarcane crops grown on other major soil types occurring throughout the Wet Tropics region before revising the SIX EASY STEPS N management guidelines.

This thesis significantly advances the application of climate forecasting indices for nitrogen fertiliser management in agricultural crops and improves the understanding of nitrogen recovery by sugarcane crops. The knowledge generated will contribute towards the development of nitrogen fertiliser management practices that will ensure both the economic and environmental sustainability of the Wet Tropics sugar industry.

Item ID: 43789
Item Type: Thesis (PhD)
Keywords: climate forecasting; climate modeling; climate modelling; crop yields; crops; Far North Queensland; fertilisering; fertilisers; fertilizers; fertilizing; nitrogen; ratoons; sugar cane; sugar industry; sugarcane; Tully; weather prediction; Wet Tropics
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Publications arising from this thesis are available from the Related URLs field. The publications are:

Chapter 1: Skocaj, Danielle M., Everingham, Yvette L., and Schroeder, Bernard L. (2013) Nitrogen management guidelines for sugarcane production in Australia: can these be modified for wet tropical conditions using seasonal climate forecasting? Springer Science Reviews, 1 (1). pp. 51-71.

Chapter 2: Skocaj, D.M., and Everingham, Y.L. (2014) Identifying climate variables having the greatest influence on sugarcane yields in the tully mill area. In: Proceedings of the Australian Society of Sugar Cane Technologists (36), pp. 53-61. From: ASSCT 2014: 36th Annual Conference of the Australian Society of Sugar Cane Technologists, 28 April - 1 May 2014, Broadbeach, QLD, Australia.

Chapter 3: Skocaj, D.M., Hurney, Alan, Inman-Bamber, N.G., Schroeder, B.L., and Everingham, Y.L. (2013) Modelling sugarcane yield response to applied nitrogen fertiliser in a wet tropical environment. In: Proccedings of the 35th Conference of the Australian Society of Sugar Cane Technologists (7), pp. 1-9. From: 35th Conference of the Australian Society of Sugar Cane Technologists, 16-18 April 2013, Townsville, QLD, Australia.

Date Deposited: 18 May 2016 04:43
FoR Codes: 01 MATHEMATICAL SCIENCES > 0104 Statistics > 010401 Applied Statistics @ 100%
SEO Codes: 82 PLANT PRODUCTION AND PLANT PRIMARY PRODUCTS > 8203 Industrial Crops > 820304 Sugar @ 100%
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