Soil health and nutrient management

Permanent URI for this collectionhttp://elibrary2.sugarresearch.com.au/handle/11079/13842

Research outcomes: Soil health is improved with a resulting positive impact on the environment and yield growth. Improved reputation and relationship between industry and environmental groups.

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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.
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”.
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.