Using a urine sensor to estimate nitrogen excretion by lactating dairy cows in Australian grazing systems

A.Ahmed1, S.R Aarons2

1 School of life sciences, Latrobe University, Bundoora, VIC, 3083,

2 Agriculture, Research and Development, Department of Economic Development, Jobs, Transport and Resources, Ellinbank, Vic, 3821,


Ruminants excrete most of their N intake, with most of the N excreted in urine. As a result, urine is the greatest contributor of N losses to the environment in dairy systems worldwide, due to the high use of N. While quantifying N excretion will assist in the development of improved N management practices, measurement of urinary N is difficult in grazing dairy systems. A urine sensor developed by AgResearch, New Zealand which allows the determination of N concentration (%) and volume of each individual excretion event performed by grazing cows was tested in Australian conditions. Twenty Friesian-cross lactating dairy cows were fitted with urine sensors and data were recorded over a 48 hour period in spring 2014 and late winter 2015. A total of 420 urination events were recorded in this study. Urine volume excreted by these grazing lactating cows ranged from 8.2 to 43 L/day while urinary N concentration varied between 1.2 and 15.7 g N/L, similar to previously reported results. The average urination frequency was 18 times per day and average volume per event was 8.2 L/event. These data also showed that N concentration varies between time of the day and showed higher concentration in the early morning and afternoon.

Using metabolomic methods in the Victorian Dairy industry to understand the importance of organic nitrogen: from factory to farm

Michael W. Heaven1, Sharon R. Aarons1, Lori Phillips2, Brunda Nijagal3, Komal Kanojia3, T. Vincent Verheyen4, Alicia J. Reynolds4, Murray Hannah1, David Nash1, Pauline Mele2, Dedreia Tull3, Amsha Nahid2

1Department of Economic Development, Jobs, Transport and Resources (DEDJTR), Ellinbank, Victoria, Australia.
2DEDJTR, AgriBio, La Trobe University, Bundoora, Victoria, Australia.
3Metabolomics Australia, Bio21 Institute, The University of Melbourne, Parkville, Victoria, Australia.
4School of Applied and Biomedical Sciences, Federation University Gippsland Campus, Churchill, Victoria, Australia.


Metabolomic techniques were used to identify metabolites that are produced and used in the dairy industry. Organic nitrogen (OrgN) compounds were identified in dairy factory wastewater streams. OrgN metabolites were predominantly found in the effluent stream and successfully segregated within the factory from recycled water streams used for irrigation and replenishment of a nearby waterway. Tolytriazoles were identified in the effluent waste water. Due to their recalcitrant nature, they have the potential to act as a marker of downstream pollution. A time based study of the dairy factory bioreactor waste waters identified another potential marker of factory productivity. The OrgN metabolite, 4-nitrophenol was found to be correlated with increasing anaerobicity of the bioreactor. The methodologies optimised from this research were used to identify OrgN metabolites in soil samples from farms in the main dairy regions of Victoria. Amino acids were the largest component of all metabolites identified. Several metabolites (e.g. cytidine) were found to be significantly changes in concentration in response to increasing potassium fertiliser application rates. These metabolites may be related to microbial or plant biochemical metabolic pathways. Microbial community analyses showed similar trends in regards to microbes (archaea, bacteria) associated with N metabolite production.

Building a Bayesian network to identify key intervention points for improving nitrogen efficiency in New Zealand dairy farm systems

Gina Lucci1, Cecile DeKlein2, Vicki Burggraaf1, Diana Selbie1 and David Pacheco3

1 AgResearch, Private Bag 3123, Hamilton 3240, New Zealand
2 AgResearch, Puddle Alley, Private Bag 50034, Mosgiel 9053, New Zealand
3 AgResearch, Private Bag 11008, Palmerston North, 4442, New Zealand


Nitrogen (N) losses from New Zealand dairy farms are, in part, due to inefficiencies in N use within the system. Nitrogen cycling in pastoral dairy farming systems is complex, and understanding the interactions and interdependencies of N sources, N use and processes that control N losses will enable a more targeted approach to improving the overall N efficiency of the system. Bayesian Network (BN) modelling is an alternative to conventional modelling as it can evaluate complex multifactor problems using both forward and backward reasoning (cause-to-effect, and effect-to-cause), as well as assign probabilities to different outcomes. We developed a BN to identify the relative contribution of different components within a NZ dairy system to N leaching losses. An initial analysis revealed that the BN model can be a valuable tool for understanding how elements of the dairy N system fit together and their relative importance to overall N loss. Preliminary results also show that N leaching was most affected by feed N content and DM intake as opposed to the breed and weight of the cow. After further validation of the model it will be used to assess how current systems can be changed to meet N leaching targets, and to identify future strategies for improving N efficiency that target the key intervention points.

Predicting N excretion in commercial grazing system dairy farms

Sharon R Aarons1, Cameron JP Gourley1, Mark Powell2,

1 Agriculture Research and Development, Department of Economic Development, Jobs, Transport and Resources, Ellinbank Dairy Centre, 1301 Hazeldean Road, Ellinbank, Victoria 3821, Australia website,

2 US Dairy Forage Research Center, USDA Agricultural Research Service, 1925 Linden Drive West, University of Wisconsin, Madison, WI 53706, USA


Improving nitrogen (N) management on dairy farms is best facilitated through management of dairy cow dietary N intakes, due to strong associations between intakes, nutrient use efficiencies and N excretion.  Milk urea N (MUN) has also been used as an indicator of excess N in dairy systems.  While a number of predictive relationships between these parameters have been developed for confinement based systems, less information is available for grazing dairy systems.  Feed intake, N excretion and MUN data were determined from samples collected at five quarterly visits over a year on 43 commercial grazing-based dairy farms representing a range of production systems (n=227).  Relationships were developed between feed N intake, excreted N, feed N use efficiency (NUE) and MUN using these data.  The regression relationships were generally similar to the prediction equations reported in the literature for confinement-based dairy systems.  The coefficient of determination for the relationship between excreted N and N intake (ExcrN = 0.84NIn – 23.6; R2=0.97) was greater than the literature, probably due to the method of estimating excreted N.  Lactating cow N use efficiency declined with N intake (NUE = -0.009NIn + 25.9; R2=0.08), but the relationship to crude protein concentration was stronger (NUE = -0.79CP + 35.9; R2=0.50).  Mean MUN for these grazing system dairy cows (12.7 mg/dL) was similar to levels reported for commercial herd and significant relationships were observed between MUN and crude protein (R2=0.19), N use efficiency (R2=0.10) and excreted N (R2=0.17).  The weaker relationships observed were most likely due to the range of breeds, milk production and feeding systems used by these farmers, in contrast to the experimental herds and confinement systems reported elsewhere.  Despite the lower R2, these relationships suggest that prediction of N intake and excretion could improve nutrient management in grazing systems.

Improving nitrogen and phosphorus response of corn (Zea mays L.) to dairy slurry by precision injection: benefits and risks

Derek Hunt1, Shabtai Bittman1, Coby Hoogendoorn2 and Hongjie Zhang1

Agriculture and Agri-Food Canada, Box 1000, Agassiz, BC, Canada, V0M 1A0,

2 Independent Researcher, 15 Beattie St, Feilding, New Zealand, 4772


We evaluated the benefits and risks of precision planting corn near dairy slurry injection furrows (DS-I) in terms of crop performance and environmental impact relative to mineral fertilizer (MF) and broadcast/ incorporated (DS-B) slurry. The study was conducted in 2010-2014 on silty loam in a cool maritime climate in south coastal BC, Canada. Injected manure improved N and P uptake and yield relative to broadcast manure at all application rates. Phosphorous (P) uptake was comparable or better than fertilizer but nitrogen (N) uptake was lower. Apparent N uptake (% of applied N adjusted for control), depending on application rates, was 53-79% for MF, 41-53% for DS-I, 36-42% for DS-B.  Crop response to DS-I plus starter (i.e. DS-I+S) approached MF for most variables and for P uptake it was higher. DS-I had about two times higher emissions of nitrous oxide (N2O) than DS-B due to greater emission peaks within a month of nutrient application; N2O emissions were slightly higher than IPCC factors for DS-I but substantially lower for DS-B. Movement of nitrate below the root zone had modest peaks after application and after summer drought but unlike N2O continued through the cool rainy season. The study showed that precision injection improves corn performance compared to conventional methods but to reach maximum yield either starter fertilizer or relatively high N manure rates are required.

Aged biochar affects gross nitrogen mineralisation and nitrogen recovery: a 15N study in two contrasting soils

Shamim Mia1, Feike A. Dijkstra1 and Balwant Singh1

1Center for Carbon, Water and Food, Faculty of Agriculture and Environment, School of Life and Environmental Sciences, The University of Sydney, Camden, NSW, 2570, Australia.

Corresponding author: Shamim Mia, email:


Biochar is pyrolysed biomass and comparatively more resistant to biodegradation than to its original biomass. When applied to soils, it could increase agricultural productivity through increased nutrient retention. Here, we examined the effects of a biochar after 21 months of application (20 t/ha) in two soil types, i.e., Tenosol and Dermosol, on gross nitrogen (N) mineralisation (GNM) and 15N recovery in a grassland field experiment using a 15N-labelled ammonium sulphate. The experiment also included a phosphorus (P) addition treatment (1 kg ha-1). The Demosol is clayey (52% sand and 29% clay) while the Tenosol is sandy (82% sand and 8% clay). We only found an increased GNM in the Tenosol, when it received both biochar and P. Biochar along with P addition possibly enhanced microbial activity in the nutrient limited Tenosol. Biochar significantly increased total 15N recovery in the Tenosol (on average by 12%) and reduced leaching to sub-surface soil layers (on average by 52%). Overall 15N recovery was greater in the Dermosol, but was not affected by biochar or P treatment. The increased N retention with biochar addition in the sandy Tenosol may be due to NH4+-N retention at cation exchange sites on aged biochar in the soil. Our results suggest that aged biochar may increase N use efficiency through reduced leaching or gaseous losses in sandy soils.

Harvest index for biomass and nitrogen in maize crops limited by nitrogen and water

  1. Chakwizira*, E.I. Teixeira, J.M. de Ruiter, S. Maley and M.J. George

The New Zealand Institute for Plant & Food Research Limited, Private Bag 4704, Christchurch, 8140, New Zealand. Phone: +64 3 3256400, Fax: +64 3 3252074

* Corresponding author: Email:


Nitrogen (N) is one of the major yield-limiting nutrients for crop production. At high application rates the efficiency of N use is reduced and the risk of N loss in soil-plant systems is increased. The N taken up by maize crops is partitioned between vegetative (e.g. leaves and stems) and reproductive organs (e.g. grains) that have economic value. The ratio of grain N to total crop N, defined as the nitrogen harvest index (NHI), provides an indication of how efficiently the plant converts absorbed N into grain. Two field experiments with the maize hybrid ‘Pioneer 39G12’ were undertaken to investigate how N rate and irrigation affected NHI and grain quality of maize grown. Harvest index (HI) and NHI increased with increasing water supply, from 0.47 to 0.53 (HI) and 0.43 to 0.60 (NHI), for the dryland and irrigated crops, respectively. However, neither HI nor NHI was significantly affected by N rate. The grain N concentration (Ng%) increased from 0.97% to 1.1% with water supply, and from 0.92% for the N control to 1.25% for the 200–250 kg N/ha crops in both experiments. However, Ng% did not significantly increase at the higher rates of fertiliser N. The NHI was closely related to HI, which suggests that management options to improve the HI of maize crops would also improve the crops’ ability to utilise N. The response of both HI and NHI to moisture stress, but not fertiliser N, highlights the importance of soil moisture in crop production in this environment, due to its influence on N uptake. Treatments with high water availability caused higher NHI values in crops and therefore we conclude that water management was of more value than N fertiliser rates for increasing NHI up to reported critical thresholds up to ±0.65.

Recovery of soil and fertiliser nitrogen in irrigated cotton in Australia

John Smith1, Mike Bell2

1 NSW Department of Primary Industries, 2198 Irrigation Way East, Yanco, NSW, 2703,,

2 The University of Queensland, School of Agriculture and Food Sciences, Gatton, QLD, 4343


Lint yield of irrigated cotton is typically responsive to the application of fertiliser nitrogen (N).  However, the applications of high rates of fertiliser N that exceed crop requirements result in unnecessarily low nitrogen recovery efficiency (NRE).  Three field experiments with eight N application rates were established across overhead and flood-furrow irrigation systems to determine N response curves for lint yield in irrigated cotton.  Lint yield was considered to be at its maximum where there was no further statistical increase from additional N application, this occurred between 145-245 kg/ha of total N supply (mineral N at planting + applied fertiliser N) with plant N uptake levels of 134-170 kg/ha.  NRE was determined by dividing crop N uptake at defoliation by the total N supply.  Where starting soil N levels were similar, overhead irrigation offered 34% higher NRE compared to flood.  The NRE at maximum lint yield was 6-28% higher than that achieved using farm practice at each site.

Dissimilatory nitrate reduction to ammonium, denitrification and anaerobic ammonium oxidation in paddy soil

Arjun Pandey1, Helen Suter1, Jizheng He1, Deli Chen1

1 Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Burnley Campus, 500 Yarra Boulevard, Richmond, Victoria 3121, Email:


Nitrogen (N) is the most important yield-limiting nutrient for rice production. Flooding of rice paddies for an extended period of time creates anoxic conditions in soil which can favour a simultaneous occurrence of several microbial N transformation processes, such as dissimilatory nitrate (NO3) reduction to ammonium (NH4+) (DNRA), denitrification and anaerobic NH4+ oxidation (anammox). Little is known about the role of DNRA and anammox in N cycling in paddy soils, and of the simultaneous occurrence of these N transformations. This study utilized a 15N isotopic approach to determine the rates of DNRA, denitrification and anammox processes simultaneously in a paddy soil. The paddy soil was collected from the Riverina region in New South Wales, Australia and studied under laboratory conditions. The rates of the processes were investigated after a week of flooding of paddy soil after a basal dose of N application at the rate of 1.6 g N m-2 (farmers practice in the region). Results showed that DNRA contributed to the formation of 0.34 µmole NH4+-N hr-1 kg-1 soil. Denitrification and anammox produced 3.35 µmole N2 and 0.65 µmole N2 hr-1 kg-1 soil, respectively. Denitrification was the major pathway contributing to N2 production which accounted for 83% of total N2 produced. Anammox contributed to 17% of total N2 production. Considering the bulk density of soil (1.3 g cm-3), it can be estimated that DNRA can retain 0.03 g N m-2 day-1, whereas denitrification and anammox can contribute to a loss of 0.58 and 0.11 g N m-2 day-1, respectively,  after the first week of flooding of paddy soil.

Regional assessment of dry and wet deposition of reactive nitrogen in East Asia

Satomi Ban1,2, Kazuhide Matsuda1

1 Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan,

2 Japan Environmental Sanitation Center, 11 10-6 Yotsuyakami-cho, Kawasaki 210-0828, Japan


In order to investigate the state of reactive nitrogen deposition in East Asia, we carried out a measurement-based assessment of nitrogen deposition on regional scale in cooperation with the Acid Deposition Monitoring Network in East Asia (EANET). We estimated the dry deposition amounts of HNO3 and NH3 in gas phase, and NO3 and NH4+ in aerosol phase by a modified inferential method using monthly mean inputs of meteorological data. Dry deposition amounts estimated by the modified inferential method well reproduce those estimated by using high time resolution inputs in the case of long-term total dry deposition (e.g. annual deposition). The total (dry and wet) nitrogen depositions at 20 sites in 7 countries in East Asia were in the range of 2.8 – 37 kg N ha-1 year-1, and high total nitrogen deposition amounts over 10 kg N ha-1 year-1 were found in wide areas of the region. The highest amount in each site classification (urban, rural, and remote) was found at Chinese sites. The ratios of dry deposition to total deposition were high in the inland areas due to the low precipitation. And the ratios of reduced nitrogen to total nitrogen deposition were relatively high in southern part of East Asia.