Soil health and nutrient management

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Improving the efficiency of nitrogen fertilisation of sugarcane under minimum till and trash conservation cultural conditions (Final report SRDC Project BS37S)
(1992) Chapman, LS; Freney, R; Denmead, OT; Wood, AW; Saffigna, PG
Objectives of the experiments were (1) Determine the extent of NH3 volatilisation when urea and ammonium sulfate are applied to the surface of a trash blanket in four cane-growing regions. Evaluate the effect of various placements of urea in a trash blanket under wet and dry moisture regimes by quantifying the amount of N recovered in the soil-plant system.
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.
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.
Final report to the Sugar Research and Development Corporation CTA007 A modelling framework to integrate research on nitrogen management of sugarcane
(1996) Keating, BA
This project used a measurement and modelling approach to explore the processes controlling nitrogen supply and losses in the crop and soil elements of sugarcane production systems. Measurements took place both in the field and laboratory. These measurements, together with data coUected from other sugarcane research projects in Australia and overseas, lead to the development of the APSIM-Sugarcane simulation model. This model captures the main elements of our understanding of sugarcane growth, yield, N uptake and utilisation and water use. APSIM is a modular modelling system, and the Sugarcane module is compatible with other APSIM modules of soil processes and crop management. Within the life of this project, APSIM-Sugarcane was used to investigate N management strategies in sugarcane production systems. A major outcome of these modelling studies was the recognition of the potential for substantial N losses via leaching in situations where N fertiliser inputs exceeded crop demands. This project drew together different threads in nitrogen research on sugarcane for the first time. Prior to this, the focus was on either empirical "rates and dates" experiments, which while underpinning current N fertiliser recommendations, were not advancing our understanding of N in the crop-soil system, and on studies of particular N processes(eg volatilisation or mineralisation), which were not integrated with one another or with the broader system performance.

Soil health and nutrient management

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