Browsing by Author "Thorburn, P"

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A review of nitrogen use efficiency in sugarcane
(2015) Bell, MJ; Biggs, J; McKellar, LB; Connellan, J; Di Bella, L; Dwyer, R; Empson, M; Garside, AJ; Harvey, T; Kraak, J; Lakshmanan, P; Lamb, DW; Meier, E; Moody, P; Muster, T; Palmer, J; Robinson, N; Robson, A; Salter, B; Schroeder, B; Silburn, M; Schmidt, S; Skocaj, DM; Stacey, S; Stanley, J; Thorburn, P; Verburg, K; Walker, C; Wang, W; Wood, A
The Great Barrier Reef (GBR) is the world's largest coral reef ecosystem, providing both substantial economic benefit to Australia and significant international ecological value. The health of the GBR is under pressure from sediments, pesticides and nutrients (especially nitrogen) discharged from nearby catchments. Discharge of nitrogen is of particular concern as it stimulates outbreaks of the Crown of Thorns Starfish, a major predator of GBR corals. Recent research has shown that the amount of nitrogen fertiliser applied in excess of crop uptake is an important determinant of nitrogen discharge from catchments, so increasing the efficiency of nitrogen use in cropping systems is an important step in protecting the economic and ecological benefits provided by the GBR. Importantly, an increase in nitrogen use efficiency (NUE) also offers opportunities to improve productivity and profitability of agricultural industries, with such benefits a major incentive for industry adoption and practice change. The Australian sugarcane industry is a significant contributor to the anthropogenic loads of nitrogen entering the Great Barrier Reef lagoon, with recent estimates in the Reef Water Quality Protection Plan (2013) suggesting it contributes 18% and 56% of particulate and inorganic nitrogen loads, respectively. A focus on improving NUE in the Australian sugar industry to reduce these loads wherever possible is a logical outcome from these statistics. While the relative impact of dissolved inorganic nitrogen (DIN) and particulate nitrogen (PN) is still uncertain, recent NUE forums in the sugar industry in 2014 identified clear target reductions in DIN that would be needed in order to significantly improve water quality in line with Reef Plan (2013-18) targets. The forum also identified a clear need for a joint industry-government funded research program to improve NUE in sugarcane cropping systems. The review conducted for this report was commissioned and funded by the Australian Government Reef Programme to provide a foundation for this joint NUE research program. The review was tasked with providing an improved understanding of past and current research effort and available field trial information (both published and unpublished) relating to nitrogen management in the sugar industry. From this perspective the review was then tasked with identifying research gaps and opportunities for future research projects and field trials that would collectively contribute to improving NUE from both agronomic and production perspectives as well as delivering significant reductions in nitrogen lost to waterways and the Great Barrier Reef lagoon. It is widely recognized that in any crop, the demand for N is determined by the size of the crop and the fundamental efficiency with which that crop produces a unit of biomass or harvested product from a kg of acquired N (N use efficiency - NUE). Therefore a good understanding of yield potential at the spatial scale of the productivity unit (i.e., farm, several blocks of similar productivity, individual blocks or within-block) about which N fertilizer management decisions (rate, form, placement, timing) are made is required, along with an understanding of how that yield potential varies with seasonal conditions. Collectively, this could be called seasonal 'block' (or productivity zone) yield potential, and it will produce a crop N demand that may vary from year to year. The sugar industry is currently operating at the district level (generally comprising several thousand cropped hectares across variable soil types and landscapes), and basing N demand for all growers in the district on the best farm yield ever achieved over a 20 year time frame. It is apparent that overall NUE could be improved by basing N fertiliser inputs on the seasonal yield potential of the productivity unit.
Adopting systems approaches to water and nutrient management for future cane production in the Burdekin SRDC Research Project CSE020 final report
(2008) Thorburn, P
There is concern about environmental impacts of cropping in catchments of Australia’s Great Barrier Reef, especially losses of nitrogen (N) and herbicides from cropping systems. Sugarcane production in the Burdekin region in the dry tropics stands out from other crops/regions because, (1) it is fully irrigated, which may enhance the losses of any chemicals from farms, and (2) it has the highest N fertiliser application rates of any sugarcane producing region in Australia. There are few measurements of N and/or herbicide losses from sugarcane production, especially fully irrigated production. More complete information is needed to evaluate, develop and underpin the adoption of management practices to reduce environmental impacts of sugarcane production. Four streams of work were undertaken to provide this information: Monitoring water quality leaving sugarcane farms. Demonstrating water quality and productivity benefits of farm management practices. Harnessing the information from these two components to describe and classify management practice systems typical of past, current and future ‘best practice’, and estimate the water quality, productivity and economic benefits of these systems. Communicating results of these activities widely within and beyond the region. Water, N and herbicide losses were measured at three sites in different parts of the Burdekin region, covering a range of soil types and irrigation managements. The experimental data were then used to parameterise the APSIM-Sugarcane cropping systems model, and then used to infill missing data and develop complete water and N balances for each of the three crops measured at the sites. N losses in runoff were relatively small, being less than 10 kg N ha-1 crop-1. Herbicide losses were similar to those measured previously. More N was lost via deep drainage than runoff at all sites, even those with slowly permeable soils. The results were consistent with the known ground water nitrate contamination issues in the region.
How much nitrogen will that crop need? Incorporating climate forecasting to improve nitrogen management in the Wet Tropics : Final project 2015/075
(Sugar Research Australia Limited, 2018) Everingham, Y; Biggs, J; Schroeder, B; Skocaj, D; Thorburn, P; Sexton, J
Determining the optimum amount of nitrogen that is required by the crop to maximise production, profitability and environmental outcomes is a challenging problem. The modelling approach taken in this project has balanced each of these complex elements to produce, and demonstrate, a novel and grower-friendly solution for the Tully canegrowing region. Optim-N Gets a Thumbs Up “How much nitrogen does my crop need?” depends on many interacting factors such as soil type, harvest management, position in the landscape and climate variability! This project took a unique and innovative approach to solving this problem and neatly embedded this process in a prototype tool called “Optim-N”. Instead of applying the same rate of nitrogen every year, Optim-N formulates nitrogen guidelines based on climate forecasts, for eight important soils in two climate zones in the Tully region, and three harvest dates. The processes behind Optim-N were tested against all available data, both from experiments and, where these were not available, expert opinion. When fully developed and operational, this tool will save farmers money by tailoring season- and site-specific recommendations for individual cane paddocks; improve water quality leaving farms and entering waterways to the Great Barrier Reef, and skill-up extension officers, allowing them to provide more targeted advice for farmers that factors in seasonal climate forecasts from the world’s best climate models. Two major activities are needed to take Optim-N from a prototype, to a widely used tool: Optim-N would need to be trialled with farmers in an action learning context so they could understand how it helps their decision making. This experience would also drive refinements of the Optim-N tool. It would also provide more empirical data for testing the science behind the tool, reducing the reliance on expert opinion and simultaneously increase trust and end-user confidence in the tool, which would accelerate adoption. The Optim-N prototype also needs input from professional software experts to take it to commercial levels of robustness and usability. When presented at a variety of forums, the Optim-N prototype receives a big “thumbs-up”.
Implementing methods for wider industry adoption : SRDC final report CSE009
(2007) Jakku, E; Everingham, Y; Inman-Bamber, G; Thorburn, P
Many of the challenges that the sugarcane industry faces are complex systems issues and R&D addressing these issues requires the active participation of industry stakeholders. A deeper understanding of processes that contribute to effective engagement between researchers and end-users is therefore essential to deal with the ongoing and evolving complexities of sugarcane systems. Without this knowledge, millions of dollars of R&D investment will be wasted and immeasurable environmental, social and economic benefits will be lost. The framework developed in this project has the potential to improve the way in which participatory research and technology development are conducted. However, in order to realise these impacts, the framework needs to be further developed to more clearly guide interactions between scientists, extension officers and farmers. Building capacity within the industry to implement learnings from this framework could help maximise the impact of complex technologies in the Australian sugarcane industry. This will assist the industry to profit rather than suffer from the complex challenges that it faces.
Improved environmental outcomes and profitability through innovative management of nitrogen SRDC research project CSE011 final report
(2008) Thorburn, P; Webster, T; Biggs, J; Biggs. I; Park, S
Nitrogen (N) fertiliser additions are an important contributor to productivity and profitability in intensive farming systems, including sugarcane production. However, applying N increases losses of N to the environment, and so all intensive agricultural industries face the challenge of maintaining productivity while minimising environmental impacts of N fertiliser use. This challenge has become particularly important for sugarcane production in Australia because community concern grows over the impact of N on the health of the Great Barrier Reef and sugarcane production has the largest use of N fertiliser in the region. It has been suggested that replacing the N lost from a crop through harvested cane and environmental losses will better align N fertiliser applications to the actual needs of sugarcane crops and the other potential sources of N available to the crop, and so improve the financial and environmental sustainability of the Australian sugarcane industry. In this project we tested and further developed an innovative N fertiliser management system, the N Replacement (NR) system.
Increasing in-mill NIR effectiveness and communicating data to all sectors for improved decision making in the sugarcane value chain : SRDC Final report CSR038
(2009) Markely, J; Griffin, D; Staunton, S; Thorburn, P; Crowley, T
In 2005 Mackay Sugar introduced changes to their cane payment formula that primarily used Near Infra Red (NIR) data as the basis for grower payments. The cane payment system was based on the principle of sharing risks and rewards, and removing obstacles to cooperation between industry sectors. The confidence gained from Mackay Sugar’s introduction of NIR technology and it’s subsequent acceptance by industry stakeholders in the Mackay Sugar region was initially the basis on which CSR developed a project proposal that sought as one of it’s objectives to further advance NIR technology in association with Global Positioning Systems (GPS) into precision agriculture (PA). Advancement in PA offered an opportunity to improve the productivity, profitability and environmental performance of the growing and harvesting sector through the use of NIR generated data. To gain the necessary benefits, further development of NIR calibrations, particularly in plant nutrients needed to be undertaken. At the commencement of the project CSR had an undertaking to introduce NIR technologies into their factories starting with an installation at Invicta Mill. Unfortunately after a series of events that eventually lead to CSR abandoning the introduction of NIR technology, the project was redefined at the start of the 2008 season under the management of Mackay Sugar staff. The failure of CSR to provide data as detailed in the original project proposal did have an effect on some outcomes and is reported in the details of the final report.
Integrating and optimising farm-to-mill decisions to maximise industry profitability : SRDC Final report CSE005
(2006) Higgins, A; Prestwidge, D; Sandell, G; Antony, G; Laredo, L; Thorburn, P
Late in the 1990’s, the Australian sugar industry recognised the need to achieve increased integration across its value chain, so as to reduce costs and increase international competitiveness. Past projects and independent assessments highlighted the harvesting and transport interface as being a high priority due to its current logistical inefficiencies and large potential economic benefits from removing these. The logistical inefficiencies were partly manifested by the social and ownership differences between these sectors. CSE005 aimed to explore and implement multiple opportunities to achieve economic benefits at the harvesting and transport interface of the value chain, using a combined participatory action research and technical modelling approach. The project used case studies, initially being the Mourilyan, Mossman and Plane Creek regions. Each case study had a local industry working group, to drive the process of building models, validation, and developing pathways to adoption. Mourilyan was the basis for the model development due to the broad range of opportunities that the region was to explore and due to its technical capacity to work closely with the research team. This research team was multi-disciplinary across CSIRO, BSES and Harvesting Solutions due to the broad range of modelling expertise required in harvesting and transport. One of the first steps with the Mourilyan case study was to conceptualise the value chain in harvesting and transport, which defined the key linkages and drivers across these sectors. This was the basis for formulating a modelling framework which defined the interactions between the industry component models, some of which already existed within the industry. A modelling framework approach was better than building a super-model since it was more transparent to the local industry working groups, more robust and had greater industry ownership. Throughout the life of the Mourilyan case study, the modelling work underwent many revisions (over a one-year timeframe) through the participatory action research process. During this process, the case study regions developed and refined options (or scenarios) for the models. This provided the case study working group with a growing understanding of best-bet options for the local region and the benefits across the participants of the chain. Opportunities identified across the case study regions collectively fell into the themes of: increased time window of harvest through staggering the start times of harvesters; harvest best practice; improved seasonal logistics; transition to larger harvesting groups; and rationalisation/upgrading of transport infrastructure. Their collective potential benefits from these options was in excess of $2.00/tc for some case studies. The increased time window of harvest option was adopted immediately in the Mourilyan and Mossman regions due to minimal change management and no capital investment requirements, and continued to be implemented throughout the life and beyond CSE005. Harvest best practice started to be piloted in Mourilyan as a result of CSE005, though its adoption was often hampered by pressure to fill bins and disruptions. Whilst the Mourilyan and Mossman regions agreed the time window of harvest options were beneficial, an evaluation based on factual data was impossible due major changes in the base line evaluation (e.g. changed number of harvesting groups, tonnes crushed at each mill) from 2002 to 2005. About mid-way through CSE005, the Mourilyan and Plane Creek case studies ended pre-maturely due to reasons beyond the control of the project team. Whilst this was a disappointment for the project team and for many of the participants in the local industry working groups, the Herbert quickly became a replacement case study.
Overcoming on-farm constraints to productivity and profitability in a wet tropical area
(2003) Goodson, M; Thorburn, P
The CCS in the wet tropics has been declining steadily for over three decades, a period in which green cane harvesting-trash blanketing (GCTB) has become standard practice among growers throughout the wet tropics. In the Babinda Mill region, where this situation is most acute, it has been hypothesised that a part of the low CCS problem is due to the effect of GCTB in increasing soil moisture and soil fertility, which aggravates lodging and suckering in the crop and restricts the opportunity for drying crops out. During the 1990’s Babinda growers were assessing alternative management systems to overcome some of these perceived problems associated with trash blanketing. This project aimed to implement best-bet initiatives to overcome problems associated with trash blanketing, and so improve productivity and profitability in a wet tropics environment. The project was directed by stakeholders and conducted using a participative approach. There were four interrelated ‘strands’ of activity undertaken in this project: 1. Liaison and interaction with Babinda growers and the wider industry, achieved through establishment of a Grower Management Group, conducting all trials on farms (as opposed to research stations), distributing regular newsletters and holding regular bus tours and shed meetings to view demonstration sites and discuss trial results. 2. Demonstration of ‘best-bet’ trash management practices (for improved profitability). Trials were established on four farms comparing the impact of raking trash from the stool and/or incorporating it into the soil. 3. Exploration of improved nitrogen fertiliser placement (for improved profitability). Trials were established on two farms comparing different placement of N fertiliser (in the ground or on the trash blanket) and different N carriers (urea and Nitram). 4. Determination of soil and plant nitrogen status in response to different soils and/or management practices. Soil and crop N status were determined in all trials and a survey of amino-N in juice from sugarcane (a good indicator deficiency and over-supply of N to the crop) from all blocks on eight farms in the region. The trash management trial sites consistently failed to demonstrate any advantage of either raking trash from the stool, incorporating trash into the soil, or doing both. Thus the extra cost of purchasing and operating a trash rake is not justified. At one site, in a flood prone area where trash blanketing is impractical, trash burning consistently gave higher yields than trash raking and incorporation. This result suggests that raking and incorporation of trash is economically disadvantageous, in the short term, in these areas. However, damage to the stool during raking caused the lower yields in the raked incorporated treatments at this site and improved methods of raking trash may overcome this problem.
Precision agriculture; an avenue for profitable innovation in the Australian sugar industry, or expensive technology we can do without? : SRDC Final report CSE018
(2007) Bramley, R; Webster, T; Thorburn, P
Precision Agriculture (PA) is an all-encompassing term given to a suite of technologies which promote improved management of agricultural production through recognition that the potential productivity of agricultural land can vary considerably, even over very short distances (a few m). The key technologies involved are yield monitors, remote and proximal sensing, the global positioning system (GPS) and geographical information systems. This project was conducted in response to the recognition by the Sugar Research and Development Corporation (SRDC) that the Australian sugar industry needs an informed basis from which to make decisions as to appropriate investment in PA. The project took the form of a review of published literature on PA and two industry workshops: the first conducted mid-project to provide the Industry Reference Group with an opportunity to review project progress and to make input to the recommendations emerging from it; the second conducted at the completion of the project to inform industry of the conclusions drawn and to promote industry input into SRDC’s priority setting with respect to future PA research. The review briefly discusses the philosophy underpinning PA, looks at PA research and application in a range of cropping systems, including sugarcane production, from around the world and considers the key drivers of short range spatial variability in these production systems. Constraints to the adoption of PA and its likely economic benefits are also considered in light of experiences from around the world. The opportunities that PA offers to the Australian sugar industry are identified, along with recommendations of further research, development and extension to facilitate its productive and profitable adoption. It is concluded that sugarcane production is ideally suited to the adoption of PA. However, a number of key tasks in Research, Development and Extension (RDE) are identified which will be required to enable its implementation in the Australian sugar industry.
Review of nitrogen fertiliser research in the Australian sugar industry
(2004) Thorburn, P
The management of nitrogen (N) fertiliser is important to the Australian sugar industry, as it is an important nutrient for sugarcane production. However, over application results in reduced profitability and sugar quality, and results in high concentrations of N in soils and water of sugarcane growing areas. An extensive review of current and past research on N fertiliser management in the Australian sugar industry was undertaken to identify possible improvements in N fertiliser management and establish priorities for future research into sustainable management of N fertiliser. The Australian sugar industry has a history of high N fertiliser usage, with applications increasing from the 1960s to the late 1990s. However, industry average sugarcane production has not kept pace with N fertiliser applications, resulting in a steady increase in N fertiliser applied per ton of sugarcane harvested. Historical and recently developed N management strategies rely on matching N applications to the predicted/expected yield of the forthcoming crop. Over-application of N fertiliser is a rational reaction by growers to uncertainty about the size of the coming crop and the long-term impact of N fertiliser on profitability – significant over-fertilisation reduces profits much less than significant under fertilisation. We suggest that past and current N fertiliser management strategies have not adequately accounted for these attitudes, and the resultant longer-term implications for soil and water quality and environmental impacts in sugarcane catchments. While long-term under application of N fertiliser undoubtedly reduces profitability, there is considerable evidence to show that greatly reducing N fertiliser applications for a single crop will not significantly reduce sugarcane production. Thus, the short-term risk of crop yields limited by N deficits is possibly much lower than generally appreciated. If this is so, a new philosophy of N fertiliser management can be developed that remove the uncertainties that drive growers to over-apply N, and so allow closer matching of N inputs to N outputs from a sugarcane system. Rather than aiming to fertilise the coming crop, it may only necessary to replace the N lost from the previous crop, the majority of which is in harvested cane and therefore be easily estimated. Over the past decade, there have been significant advances in our ability to simulate N (and carbon) dynamics in sugarcane production systems. We drew upon these advances to undertake a ‘desktop’ examination of this new ‘replacement’ N management strategy. Three N management scenarios were simulated: (1) the ‘replacement’ strategy, (2) the current recommended strategy and (3) the average amounts of N applied in the industry (i.e., 30 % greater than those recommended). The replacement strategy had similar productivity, greater profitability and lower environmental N losses, whether we simulated potential crop production or a more realistic level of production (resulting from the impact of pests, diseases, lodging, stool damage, etc.). Moreover, these advantages were greater in the simulations of realistic yields. The ‘replacement’ strategy is an evidence based, transparent and defensible N management strategy, all attributes that are important for the sugar industry to maintain self-regulation of N fertiliser management. We suggest that this strategy warrants further testing, through both simulation and field experiments.
Short and long term impacts of green cane trash blanketing on soil fertility
(2005) Thorburn, P; Kingston, G
In the last three decades, there has been a widespread adoption of green cane harvesting-trash blanketing (GCTB) in the Australian sugarcane industry, generally motivated by the practical advantages (e.g. weed control, easier harvesting in wet times, etc.) associated with the GCTB farming system. While many studies have been conducted on the impact of trash blanketing on issues such as yield, soil erosion and soil physical properties, surprisingly little is known about the fate of nutrients in trash (whether burnt or retained), the decomposition of trash blankets, or impacts of GCTB on soil fertility and hence fertiliser management. This project aimed to provide information on these issues and so determine if canegrowers need to change their nutrient management strategies when they switch from burnt cane harvesting to a GCTB system. Principal findings from this project are: • Burning trash reduces trash dry matter by 70 % (pre-harvest burn) to 95 % (pre- and postharvest burn), and the loss of nutrients when trash is burnt is strongly related to the loss of dry matter. Thus GCTB can substantially increase organic matter and nutrient retention. • Rainfall will quickly leach some nutrients, especially potassium (K), from freshly harvested trash into the soil. • Trash decomposes slower than expected from its biochemical composition, with up to 10% of trash deposited on the soil after harvest still present one year later. However, the decomposition of trash can be accurately predicted across soils types and climates from sugarcane-specific residue decomposition models. • Trash blanketing, for up to 17 years, increases soil organic carbon (C) and nitrogen (N) concentrations in the top 50-100 mm of soil, but has negligible impact on concentrations of other nutrients in the soil. • The presence of trash blankets increases denitrification by 20 % on waterlogged, heavy soils in the period immediately following applications of N fertiliser. Denitrification in this situation could be accurately modelled, and this modelling provided the first test of the denitrification sub-model in The Agricultural Productions Systems Simulator (APSIM). • K from trash is plant-available, so fertiliser and trash K should have similar value as nutrients. However, there was not a significant yield response to K from trash in either pot or field experiments, possibly due to variability in the results. Thus it is not clear that recommendations of K management in trash-blanketed crops should differ from those for burnt crops. • Simulation studies of N dynamics in GCTB systems suggest that: o There may be a negative, short-term impact of trash blanketing on sugarcane yields for at least 5 years after initiating GCTB. This is due to the immobilisation of N by the decomposing trash. During this time it is important that N applications not be reduced below those used when trash was burnt. Following that time; o N fertiliser applications to ratoon crops in GCTB systems should be maintained at rates appropriate for burnt systems, despite N in trash being recycled in the GCTB 2 SUGAR RESEARCH & DEVELOPMENT CORPORATION FINALREPORT - PROJECT NO. CTA022 system. The additional N from trash is immobilised by decomposing trash blankets or lost to the environment. o In plant crops, N fertiliser applications in GCTB systems could be reduced to half that recommended for burnt systems. o Average environmental losses of N, from both denitrification and leaching, are likely to be greater from GCTB systems at all rates of N fertiliser (i.e. less than, equal to or greater than optimal rates) so particular caution should be taken to avoid overapplication of N in GCTB systems. During the project, information was disseminated through the industry in numerous presentations given at field days, shed meetings, Mill Supplier Committee meetings, CRCSugar meetings (at which BSES extension officers were present), ASSCT, etc. In addition, a series of workshops was run in collaboration with CRC-Sugar on the impact of trash blanketing on soil fertility and fertiliser management. The workshops were aimed at BSES, productivity board and fertiliser company advisers, and conducted using a participatory approach to information exchange, based on adult learning principles. 3