Browsing by Author "Schmidt, S"

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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.
SaveN Cane : developing selection tools for N-efficient sugarcane
(2015) Schmidt, S; Lakshmanan, P; Cox, M; Robinson, N
This project supports the sugar industry’s intensifying efforts to reduce its nitrogen (N) footprint that is caused by inefficient use of N fertiliser by the crop. The industry aims to minimise N pollution of coastal waters and emission of potent greenhouse gas nitrous oxide from soil without negatively impacting the economic sustainability of sugar production. International research addressing this pervasive problem in grain and other crops indicates that effective approaches combine agronomic innovation of N supply and nitrogen-use efficient (NUE) crop varieties. This UQ-SRA collaborative project, aimed to advance knowledge of N use efficiency of crop varieties through systematic testing of a considerable number of sugarcane clones with diverse genetic background (commercial varieties from Australia and overseas, identified water-use-efficient clones, crosses with ancestral canes). Additional value was derived from a collaboration with QLD DAFF (Andrew Robson) to advance remote sensing of crop N, and investigations of the effects of N fertiliser on soil biology (Graham Stirling-nematodes, UQ consortium-bacterial and fungal communities). Brazilian researchers (Sao Paulo State) have since established sister experiments based on this project. Clones were cultivated with low or recommended N rates (20-40 or 160-200 kg N-fertiliser per year) in two field trials (Mackay, Burdekin). The contrasting N rates were based on concepts that (i) NUE traits are only obvious in low-N environments, and (ii) ideal crop varieties will be strongly responsive to N supply and efficiently acquire N from fertiliser and indigenous soil reserves. NUE traits of 64 clones were characterised over three years (plant crop-1st ratoon crop-2ndratoon crop) by quantifying the effects of contrasting N supply on growth in early, mid and late season. Clone vigour and ratooning ability were evaluated, as was canopy development and photosynthetic performance, the ability to acquire and store nitrate, N allocation to stalks and leaves, and sugar and biomass yields. Project deliverables focused on generating knowledge on the genetic variation in N response and NUE traits and ranking of clones across environments with different soils to study the magnitude and the robustness of NUE traits. The overall deliverables and key findings include: (i) Establishment of field experimental conditions with limited N availability suitable for screeningsugarcane populations for NUE and N-related crop attributes. The field trial set-up was demonstrably effective in evaluating a considerable number of clones over a 3-year crop cycle; (ii) Knowledge of genetic variation for NUE in Australian sugarcane germplasm; (iii) NUE screening for photosynthetic performance, N uptake and accumulation attributes and yield parameters (CCS, sugar and biomass yields) identified benefits/drawback of experimental approaches; (iv) Generated data on trait variation across clones, crop stages and environments, demonstrating that environmental conditions markedly affected crop performance as evidenced by moderate (22%, Mackay) and strong (45%, Burdekin) reduction in yields with low N supply. Soil characteristics are a likely cause as clones at Mackay acquired on average 3- and 2-fold more N than at the Burdekin site over the plant-1st ratoon cycles at low and recommended N supplies; (v) Plant vigour appears to be a major determinant of NUE in sugarcane; (vii) Clones with contrasting NUE and N response have been identified for use in next-step NUE trait research; (viii) Remote sensing showed potential for screening sugarcane germplasm, but its application at early stages of crop growth requires further investigation. Taken together, the project has achieved the stated objective and fulfilled a role in SRA’s focus area of (1) optimally-adapted varieties, Plant breeding and release. The project outcomes have been communicated to the industry nationally and internationally, have been evaluated in the context of global efforts in advancing NUE in crop and cropping systems, and are in preparation for peer review and publication in highly ranked international scientific journals. The project is strongly aligned with industry interests as evidenced by interest of growers, national and international collaborators. Logical next steps towards developing N use-efficient sugarcane in the Australian breeding program include advancing understanding the basis of clone sensitivity to N and tools for rapid selection of N-responsive clones.
SRDC Research Project Harnessing soil biology to improve the productivity of the new sugarcane farming system
(2010) Schmidt, S; Schenk, P; Lakshmanan, P
This project addresses the knowledge gap of how management affects soil biological processes. This is important because management has to maximise soil health and nutrient relations. Knowledge of soil biology in context of management strategies will allow optimising economic and environmental outcomes for the sugar industry. The project assessed how management options of the ‘new sugarcane farming system’ (reduced tillage, legume break crop, trash blanketing, and reduced nitrogen (N) fertiliser application), impact soil biology. We examined the functional groups and activity of soil microbes in context of soil N availability and gaseous emissions. Sugarcane soils in North and Southern Queensland, including the Yield Decline Joint Venture site in Ingham and two commercial farms with contrasting management practices in Bundaberg, were used for this research. A suite of well established and new methods were applied to analyse soil biological processes. A focus on soil microbiological processes is justified because microbes are the main drivers of N turnover in soil. Microbes supply N to crops by breaking down complex organic matter and soil-bound N, but also compete with plants for more easily-accessible N. Microbes convert N into easily leachable nitrate and gaseous N forms and are drivers of carbon (C) turnover in the soil. These microbial processes have not been comprehensively studied in sugarcane soils with different management. A special focus of this study was the development and application of novel molecular techniques to monitor soil microbial gene expression. This approach allows microbial functional analysis by treating soil as a “super organism” rather than deducing function from the presence of particular microbial taxa which is biased towards known microbial taxa.