Towards a complete nitrogen budget from subtropical dairy farms: three years of pasture nitrogen losses in surface runoff

David Rowlings1, Martin Labadz1, Clemens Scheer1, Peter Grace1

1 Queensland University of Technology, 2 George Street Brisbane, Queensland, 4000,


Dairy represents one of the most intensive and nitrogen (N) loaded production systems in the high rainfall regions of Queensland, Australia. Fertiliser application rates during the winter rye grass season (April-October) frequently surpass 300 kg N ha-1 year-1 yet the fate of much of the applied N is uncertain. The high (>1200 mm year-1) and intensive rainfall and the proximity to environmentally sensitive areas such as the Great Barrier Reef make losses in surface water run-off of particular interest to the industry. Two run-off plots (416 m2) were installed on an intensively irrigated and fertilised rye-grass/kikuyu pasture rotation near Gympie, Queensland and monitored over three (1 June to 31 May) measurement years. Runoff was measured using a tipping bucket and nutrients collected via an automated sampler. Runoff and losses were largest during the 2012-13 season when five of the nine runoff events over the measurement period occurred and total runoff exceeded 480 mm, corresponding to 37% of the annual rainfall. Total N load was dominated by NO3, with largest losses during a four day, 448 mm rain event in January 2013 following an extended dry period resulting in 280 mm of runoff and 16.5 kg ha-1 of N losses.  Total N losses over the remaining periods were typically negligible (< 1 kg ha-1­ event-1), with annual losses of 5.0 and 0.7 kg N ha-1 for 2013-14 and 2014-15 respectively. These results indicate that under current management systems intensive pastures contribute only minor nutrient loads, though losses can be high following extended dry periods.

Is lichen δ15N an indicator of nitrogen pollution and a surrogate of nitrogen atmospheric composition? Evidence from manipulative experiments

Silvana Munzi1, Cristina Branquinho1, Cristina Cruz1, Cristina Máguas1, Ian Leith2, Lucy Sheppard2, Mark Sutton2

1 Centre for Ecology, Evolution and Environmental Changes (cE3c), Faculdade de Ciências, Universidade de Lisboa, Bloco C2, 5º Piso, sala 2.5.14, 1749-016 Lisbon, Portugal

2 Centre for Ecology & Hydrology (CEH) Edinburgh, Bush Estate, Penicuik, EH26 0QB, UK


Due to the relevance of nitrogen (N) as a pollutant, setting up an effective method to determine spatial distribution of N sources would help to develop management and mitigation strategies. Although promising, the use of isotopic signature of lichens to map atmospheric N deposition is still difficult due to the synergism between climatic and anthropogenic factors and the superimposition of multiple N sources. To understand how lichen’s isotopic signature is affected by N, thalli of the sensitive Evernia prunastri and of the tolerant Xanthoria parietina were exposed for ten weeks to different forms and doses of N in a manipulative experiment, and physiological parameters, total N, δ15N and chlorophyll a fluorescence were measured. In parallel, thalli of Cladonia portentosa exposed to the same treatments for 11 years or 6 months were analyzed to investigate the role of time of exposure. Our results showed that lichen N content and δ15N were correlated with the N dose of the N treatments and that lichen δ15N tended to become similar to the source’s signature. However, nitrophytic and acidophytic species showed different δ15N in response to the same treatments, probably due to their cation exchange capacity. Finally, the correlation between N content and δ15N was higher in case of long-term exposure. Nitrogen isotopic signature in lichens can potentially be used as indicator to determine spatial distribution of N sources in the field. However, further investigation is needed to confirm these results in the field, and species functional traits must be taken in particular consideration.

Assessing the feasibility and net costs of achieving water quality targets: A case study in the Burnett-Mary region, Queensland, Australia

Beverly1, A. Roberts2, F.R. Bennett3

1 Agriculture Research and Development Division, Department of Economic Development, Jobs, Transport and Resources, Victoria,

2 Natural Decisions Pty Ltd, Victoria.

3 Burnett Mary Regional Group for Natural Resource Management, Bundaberg, Queensland.


This paper describes the construction of a bio-economic optimisation framework to evaluate the feasibility and net profit (or net costs) of achieving water quality targets in the Burnett-Mary region within the southern portion of the Great Barrier Reef (GBR), southern Queensland, Australia.  Key outcomes from the study were that current sediment, nitrogen and phosphorus load reduction targets could be achieved whereas more ambitious ecologically relevant targets required significant additional investment and were not feasible based on the model if individual basins must meet the targets.

High N retention in Mediterranean catchments enhanced by water management practices

Estela Romero*1,2, Josette Garnier1,3, Gilles Billen1,3, Franz Peters2, Luis Lassaletta1,4

1 Université Pierre et Marie Curie (UPMC), UMR 7619 Metis, Paris, 75005, France. Email:

2 Institut de Ciències del Mar (CSIC), Barcelona, 08003, Spain

3 Centre National de la Recherche Scientifique (CNRS), UMR 7619 Metis, Paris, 75005, France

4 PBL, Netherlands Environmental Assessment Agency, 3721 MA, Bilthoven, The Netherlands


The share of nitrogen (N) that is exported to the sea or accumulated on land (N retention, sensu lato) involves different environmental processes; coastal eutrophication and anoxia in the first case; the acidification of soils, the emission of ammonia and greenhouse gases, and the pollution of aquifers in the latter. Nevertheless, the factors involved in N retention are still poorly constrained, particularly in arid and semi-arid systems. The present study evaluates the N fluxes of 38 catchments on the Iberian Peninsula with contrasting climatic characteristics (temperate and Mediterranean), land uses, and water management practices. The contribution of physical and socio-ecological factors in the retention of N was partitioned, and the link between N retention and water regulation was explored. We hypothesize that the extreme flow regulation performed in the Mediterranean enhances the high N retention values associated with arid and semi-arid regions. Our results show that reservoirs and irrigation channels account for >50% of the variability in N retention values, and above a certain regulation threshold, N retention peaks to values >85-90%. Future climate projections forecast a decrease in rainfall and an increase in agricultural intensification and irrigation practices in many world regions, and notably in arid and semi-arid areas. Increased water demands will likely lead to a higher flow regulation, and the situation may resemble that of Mediterranean Iberian Peninsula catchments. High N retention and the associated environmental risks must therefore be considered as an important consequence of water regulation practices, and must be adequately managed.

Addressing the nitrogen problem in sugarcane production to reduce pollution of the Great Barrier Reef

N Robinson 1, R Brackin1, C Paungfoo-Lonhienne1, T Lonhienne2, M Westermann1, M Salazar1, YK Yeoh3, P Hugenholtz3, MA Ragan4, M Redding5, C Pratt5, WJ Wang6, A Royle7, L DiBella7, P Lakshmanan8, S Schmidt1

1 School of Agriculture and Food Science, The University of Queensland, Brisbane QLD 4072, Australia

2 School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane QLD 4072, Australia

3Australian Centre for Ecogenomics, School of Chemistry and Molecular Biosciences, The University of Queensland

4 Institute for Molecular Bioscience, The University of Queensland, Australia

5 Department of Agriculture and Fisheries, 203 Tor Street, Toowoomba, Qld 4350, Australia.

6 Department of Science, Information Technology and Innovation, 41 Boggo Road, Dutton Park QLD 4102, Australia

7 Herbert Cane Productivity Services Limited, Ingham QLD 4850, Australia

8 Sugar Research Australia, Indooroopilly, QLD 4068, Australia


The N pollution footprint of sugarcane cropping is large due to inefficiencies caused by mismatched N supply and crop N demand over sugarcane’s long N accumulation phase. The Great Barrier Reef lagoon receives excessive N loads that contribute to the rapidly declining reef health. Exceeding international average nitrous oxide emission rates several fold, sugarcane soils contribute significantly to Australia’s agricultural emissions. Nitrogen pollution reduction schemes over recent decades have mostly targeted reducing N fertiliser rates in line with expected yields and improving soil quality. Overall, these measures have not resulted in the desired N pollution reduction and further innovation is needed to address this problem. We present research that aims to aid agronomic innovation with (i) next-generation fertilisers that are based on repurposed nutrient-rich wastes and sorbent materials to better match N supply and crop demand and to improve soil function and carbon levels, (ii) understanding of soil N cycling and microbial processes, (iii) legume companion cropping as a source of biologically fixed N, and (iv) genetic improvement of sugarcane that more effectively captures and uses N. We conclude that evidence-based innovation has to support crop growers across climate and soil gradients in the 400,000 hectares of catchments of the Great Barrier Reef. This should include investment into new technologies to support ecologically-sound agriculture and a circular economy without waste and pollution.

Tracking Sources of excess nitrate discharge in Lake Victoria, Kenya for improved Nitrogen use efficiency in the catchment

Benjamin K. Nyilitya1, Stephen Mureithi2, Pascal Boeckx3

1 Department of Water Resources Management, Ministry of Water and Irrigation, Kenya (

2 Department of Land and Water Management, University of Nairobi, Kenya

3 Department of Applied Analytical and Physical Chemistry, Ghent University, Belgium (


A study was conducted in three major rivers (Nzoia, Nyando, Sondu) draining the Kenyan side of L. Victoria catchment to establish sources of excess nitrate deposition into the Lake using isotopic techniques and hydrochemistry. Results show spatial variation in isotope signatures with enrichment in δ15N and δ18O values near towns and industries. For instance R. Nzoia after Eldoret town had δ15N and δ18O values of 13‰, 6‰ respectively while the river after Mumias sugar factory had 9‰, 10‰ isotope values respectively. A plot of δ15N versus δ18O indicates that most of nitrate from the three catchments originates from Soil Nitrogen and manure or sewage. This may be due to deforestation, charcoal burning, untreated effluent discharges amongst other environmental degradation and poor sanitary practices rampant in the area. However, sewage and industrial effluents has high contribution to river and ground water nitrate near towns and densely populated areas as observed by the enriched δ15N values for Kisumu City Rivers ranging 10‰ to 18‰. Low nitrate content with corresponding high δ15N and δ18O signatures was observed in ground water near Kisumu city indicating denitrification takes place in the area. In addition, surface water in Kisumu had similar and enriched nitrate isotope signatures to ground water indicating high ground water susceptibility to pollution by surface water. This observation is supported by stable water isotope data (δ 18O, δ 2H) which show that the source of groundwater in Kisumu area is evaporated surface water.

Increasing nitrogen use efficiency in agriculture reduces future coastal water pollution in China

Maryna Strokal1,2, Carolien Kroeze2, Mengru Wang2,3, Ang Li2,3, Lin Ma3

1 Environmental Systems Analysis Group, Wageningen University, Droevendaalsesteeg 3, 6708 PB Wageningen, The Netherlands,, 

2 Water Systems and Global Change Group, Wageningen University, Droevendaalsesteeg 3, 6708 PB Wageningen, The Netherlands

3 Key Laboratory of Agricultural Water Resource, Center for Agricultural Resources Research, Institute of Genetic and Developmental Biology, Chinese Academy of Sciences, Huaizhong Road 286, Shijiazhuang, Hebei 050021, China


Chinese agriculture has been industrializing since the 1990s to produce enough food. This increased nitrogen (N) in Chinese rivers and coastal waters, resulting in eutrophication-related problems. We analysed three options to reduce future N pollution of coastal waters in China by 2050. We did it using the MARINA Nutrient model (a Model to Assess River Inputs of Nutrients to seAs). Two optimistic scenarios (OPT-1 and OPT-2) were developed, taking the Global Orchestration scenario (GO) of the Millennium Ecosystem Assessment as a baseline. These scenarios assume efficient N management in agriculture (OPT-1 and OPT-2) and sewage (OPT-2). We also assessed effects of the “Zero growth in fertilizer use after 2020” policy (the CP scenario). Results show that N management in agriculture is more effective to reduce future N pollution of coastal waters than N management of sewage. In GO, Chinese rivers are projected to export 38-56% more N in 2050 than in 2000 because of poor manure management. The current policy in agriculture (CP) may not be successful to reduce coastal water pollution. In contrast, our more optimistic scenarios project much lower river export of N in 2050 (at around levels of 1970 for northern rivers and 2000 levels for central and southern rivers). This is mainly because OPT-1 assumes high rates of manure recycling, leading to decreased use of synthetic fertilizers. Improved sewage management in OPT-2 can further reduce N export by northern rivers. Our results can serve as a basis for decision makers on N management.

The effect of residence time and hypoxia on nitrogen loading in the Yarra River Estuary, Australia

Keryn Roberts1, Michael Grace2, Perran Cook2

1 Water Studies Centre, Monash University, Wellington, Clayton, Victoria, 3800, Australia,

2 Water Studies Centre, Monash University, Wellington, Clayton, Victoria, 3800, Australia


Estuaries provide the final stage of nitrogen processing before its release into coastal waters. However, residence time, oxygen conditions and hydraulic mixing determine the nitrogen removal capacity of an estuary. Long residence times can lead to low oxygen conditions significantly affecting nutrient transformation pathways including, but not limited to, inhibition of nitrification and the competition for nitrate between denitrification and dissimilatory nitrate reduction to ammonium (DNRA). The study site for this research, the Yarra River estuary, is a shallow (3 – 5m) salt wedge estuary prone to hypoxia resulting from the extended residence time of the bottom waters during low flow events. The estuary is one of the main freshwater nitrogen inputs into Port Phillip Bay (PPB), a nitrogen limited system. This research examined nitrogen processing over the period 2009 – 2011, extending over two summers of contrasting rainfall. Nitrogen loads were driven by rainfall in the catchment and ensuing freshwater inflow. NO3 was the main form of dissolved inorganic nitrogen (DIN) entering the system, being 87 ± 2 % of total DIN. Low oxygen conditions promoted nitrogen recycling within the system leading to an accumulation of NH4+ in the stratified bottom waters of the estuary. Estimates of nitrogen removal were low for the Yarra River estuary at < 5% of total DIN compared to 20 – 50 % for other estuarine systems. This study highlights the importance of understanding estuarine specific conditions (residence time and oxygen) on nitrogen dynamics in the management of nitrogen loads into receiving waters.

Does nitrogen-induced forest carbon sequestration offset agricultural N2O emissions? – A meta-analysis of nitrogen addition effects on carbon sequestration in tree woody biomass

Lena Schulte-Uebbing1, Wim de Vries1,2

1 Environmental Systems Analysis Group, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands,,
2 Alterra, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands


Agricultural nitrogen (N) use leads to nitrous oxide (N2O) emissions, which contribute to climate change. However, elevated N deposition may also increase net primary productivity in N-limited terrestrial ecosystems and thus enhance the terrestrial carbon dioxide (CO2) sink. This indirect effect can lead to a considerable reduction of the net climatic impact of agricultural N use.

We performed a meta-analysis on data from 63 forest fertilization experiments to estimate N-induced carbon (C) sequestration in above-ground tree woody biomass (AGWB), a relatively stable C pool with long turnover times. Results show that boreal and temperate forests respond strongly to N deposition and store on average an additional 23 and 12 kg C per kg N in AGWB, respectively. Sub-tropical and tropical forests show much weaker response to N addition (6 and 2 kg C per kg N, respectively).

We estimated global C storage in tree AGWB resulting from agricultural N use by multiplying the C–N responses obtained from the meta-analysis with ammonia (NH3) deposition estimates per forest biome. We thus derive a global C sink of about 84 (47–120) Tg C yr-1 in AGWB, which compensates on average 16 (9–23) % of N2O emissions from agriculture (6.4 Tg N2O yr-1 or 520 Tg CO2-Ceq yr-1). Adding estimates for N-induced C sequestration in soils and below-ground woody biomass obtained by stoichiometric scaling, we estimate total forest C sequestration resulting from agricultural N use at 236 (147–341) Tg C yr-1, or 40 (28–54) % of agricultural N2O emissions.

Ecosystem services impacts associated with environmental reactive nitrogen release in the United States

Jana E. Compton1, Daniel J. Sobota2, Jiajia Lin3, and Mario Sengco4

1U.S. EPA Office of Research and Development, Western Ecology Division, Corvallis OR 97333
2 Environmental Solutions Division, Oregon Department of Environmental Quality, 811 SW 6th Avenue, Portland OR
3 National Research Council, National Academies of Science, Washington DC 20001, based at US EPA Western Ecology Division
4 U.S. EPA Office of Water, Office of Science and Technology, Washington DC 20460

Nitrogen (N) release to the environment from human activities can have important and costly impacts on human health, recreation, transportation, fisheries, and ecosystem health. Recent efforts to quantify these damage costs have identified annual damages associated with reactive N release to the EU and US in the hundreds of billions of US dollars (USD). The general approach used to estimate these damages associated with reactive N are derived from a variety of methods to estimate economic damages, for example, impacts to human respiratory health in terms of hospital visits and mortality, willingness to pay to improve a water body and costs to replace or treat drinking water systems affected by nitrate or cyanotoxin contamination. These values are then extrapolated to other areas to develop the damage cost estimates that are probably best seen as potential damage costs, particularly for aquatic ecosystems. We seek to provide an additional verification of these potential damages using data assembled by the US EPA for case studies of measured costs of nutrient impacts across the US from 2000-2012. We compare the spatial distribution and the magnitude of these costs with the spatial distribution and magnitude of costs from HUC8 watershed units across the US by Sobota et al. (2015). We anticipate that this analysis will provide a ground truthing of existing damage cost estimates, and continue to support the incorporation of cost and benefit information into communication, outreach, and decision-making related to nutrient pollution.