Dynamics and mineralisation of nitrogen in soil fertilised with brown coal-urea blends

Biplob K. Saha1*, Michael T. Rose2, Vanessa Wong3, Timothy R. Cavagnaro4 and Antonio F. Patti1

1School of Chemistry, Monash University, Clayton, Victoria, 3800, Australia

2NSW Department of Primary Industries, Wollongbar Primary Industries Institute, Wollongbar, NSW 2477, Australia

3School of Earth, Atmosphere & Environment, Monash University, Clayton, Victoria, 3800, Australia

4School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, South Australia, 5064, Australia

*Corresponding author. Email: biplob.saha@monash.edu


Increasing the efficiency of nitrogenous fertilisers is becoming more important due to detrimental effects of N loss on the environment. The addition of humic rich brown coal (BC) as an organic amendment can alter N cycling by reducing its losses in different ways. However, the effect of brown coal-urea (BCU) blends on N cycling is poorly understood. Therefore, a glasshouse incubation study was conducted to assess the effects of BCU blends on the transformation and transport of N in soil. Blending of urea with BC slowed down the fertiliser N release resulting in higher N retention over a longer period of time compared to urea. Over the two-month study, compared to urea, BCU blends generally suppressed total N2O and NH3 emissions by 31% and 43%, respectively. Incorporation of BCU blends in soil maintained significantly higher amounts of mineral and mineralisable N in soil compared to urea application only. This is supported by the leachate analysis data, which showed that less mineral N was leached from soil in the BCU blends compared to urea. The blends with higher proportions of BC had lower NH3 emissions and maintained higher mineral N in soil compared to the blend with lower proportion of BC. Moreover, addition of BCU blends increased the organic carbon content of soil. The overall results suggest that blending of urea with BC can strongly reduce N losses via leaching and gaseous emissions. As a result, greater amounts of fertiliser N will be available to crops over a longer time period, increasing the fertiliser N use efficiency and soil health.

Effects of a nitrification inhibitor on the metabolic activity of ammonia oxidisers

Xiuzhen Shi1, Hang-Wei Hu1, Ji-Zheng He1, Deli Chen1, Helen Suter1

Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria 3010, Australia


The nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) is a powerful tool that can be used to reduce N losses from agricultural systems by slowing nitrification and promote nitrogen (N) use efficiency. Mounting evidence has confirmed the functional importance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in nitrification and N2O production, however, their responses to DMPP amendment and the possible reasons for the variable efficacy of DMPP across different soils are not well known. Here we compared the effects of DMPP on the abundance and metabolic activity of ammonia oxidizers using quantitative PCR and 13CO2-DNA-stable isotope probing (SIP) method in an acidic pasture soil and an alkaline vegetable soil. Results showed that DMPP significantly inhibited nitrification in the vegetable soil only, and this was coupled with a significant decrease in AOB abundance. The 13CO2-DNA-SIP results indicated the involvement of AOA and AOB in active nitrification in both soils, but DMPP only inhibited the assimilation of 13CO2 into AOB in the vegetable soil. Our findings provide evidence that DMPP could effectively inhibit nitrification through impeding the abundance and metabolic activity of AOB in the alkaline vegetable soil, but not in the acidic pasture soil possibly due to the low AOB abundance or the adsorption of DMPP by organic matter.

Nitrapyrin with nitrogen can improve yield or quality of wheat, grass pasture, canola or sugarcane in Australia

Greg.S. Wells1

1 Dow AgroSciences Australia Ltd, PO Box 838, Sunbury, Victoria, 3429, www.dowagro.com/en-au/australia, wells1@dow.com


Nitrapyrin has been used extensively in the USA to stabilise applied nitrogen particularly for maize production.  In 2012 nitrapyrin (product name eNtrenchTM Nitrogen Stabiliser) was approved by National Industrial Chemicals Notification and Asessment Scheme (NICNAS) for use in crops including wheat, sorghum, maize, sweet corn and cotton in Australia.  It is the only product that has undergone this type of review for approval for use in Australia.

This paper reports on field research trials to determine whether nitrapyrin use improved yield or quality in crops or ryegrass in Australia.  Research to date has shown the the potential value of nitrapyrin to improve nitrogen use efficiency and to mitigate nitrous oxide emissions.  This paper will focus on field research trials to demonstrate improved nitrogen use efficiency.

Residual effect of nitrification inhibitors enhances NUE in a cropping system

Quemada, M.1, Alonso-Ayuso,M.1, Gabriel, JL.1

1 Technical University of Madrid (UPM), Ciudad Universitaria, Madrid, 28040. miguel.quemada@upm.es


Nitrification inhibitors (NI) may increase the recovery of N fertilizer applied to a crop, but little is known about the effect on the soil N supply capacity over time and the recovery by the subsequent crops. During two seasons, a field experiment with maize was fertilized with ammonium sulfate nitrate (ASN) and DMPP blended ASN (ENTEC®) at two levels (130 and 170 kg N ha-1). A control non-fertilized treatment was included. Maize yield, grain quality, nutritional state and N use efficiency were evaluated. During a third experimental season, a non-fertilized sunflower was planted in the same plots to study the cumulative effect. Laboratory determinations were performed to elucidate possible sources of residual N. The second year, DMPP application allowed a 23% reduction of the fertilizer rate without decreasing crop yield or grain quality. In addition, the non-fertilized sunflower scavenged more N in treatments previously treated with ENTEC® than with ANS, increasing N use efficiency. After DMPP application, N was conserved in non-ready soil available forms during at least 1 year and subsequently released to meet crop demand. The potential N mineralization obtained from aerobic incubation was higher for soils from the ENTEC® treatments. A higher δ15N in the soil indicated larger non-exchangeable NH4+ fixation in soils from the plots treated with ENTEC® or ASN-170 than from the ASN-130 or the control. These results open the opportunity to increase N efficiency in crop rotations by taken advantage from the effect of NI on the soil residual N.

Dual effects of nitrification inhibitors on agricultural N2O emission

Shu Kee Lam1, Helen Suter1, Rohan Davies2, Mei Bai1, Jianlei Sun1, Arvin R. Mosier1 and Deli Chen1*

1 Crop and Soil Science Section, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, VIC 3010, Australia, Email: shukee.lam@unimelb.edu.au

2 BASF Australia Ltd., Level 12, 28 Freshwater Place, Southbank VIC 3006, Australia


Nitrification inhibitors are effective in decreasing nitrous oxide (N2O) emission from agricultural systems worldwide, but can increase ammonia (NH3) volatilization and subsequently, indirect N2O emission. This is often neglected when evaluating the inhibitors as a climate change mitigation tool.  In our recent literature review, we found that when the indirect N2O emission from deposited NH3 was considered, the overall impact of nitrification inhibitors ranged from –4.5 to +0.5 kg N2O-N ha–1. We noted that no such experiment was reported in the literature for vegetable production systems, which have high risk of NH3 and N2O loss from high N input (as manures and synthetic fertilizers) and high water input. We therefore conducted a case study field experiment to simultaneously quantify the effect a nitrification inhibitor, 3,4-dimethylpyrazole phosphate (DMPP) on NH3 and N2O emissions from surface applied chicken manure and synthetic fertilizers in a vegetable production system using a micrometeorological approach. The cumulative NH3 emissions over the measurement period were 19.7 and 27.0 kg N ha–1 for the control and DMPP treatment (an increase of 7.3 kg N ha–1, or 37% with DMPP). The corresponding values for the cumulative direct N2O emission over the measurement period were 6.0 and 3.8 kg N ha–1 (a decrease of 2.3 kg N ha–1, or 38% with DMPP). This suggests that the beneficial effect of nitrification inhibitors in decreasing direct N2O emission may be undermined by the concomitant increase in NH3 volatilization.

Effects of the novel nitrification inhibitor DMPSA on yield, mineral N dynamics and N2O emissions

Andreas Pacholski1, Nils Berger1, Ivan Bustamante2, Rainer Ruser2, Guillermo Guardia3 ,Thomas Mannheim1

1 EurochemAgro GmbH, Reichskanzler-Müller-Str. 3, Mannheim, Germany, 68165, www.eurochemagro.com, Andreas.pacholski@eurochemgroup.com

2 Hohenheim University, Institute of Crop Science, Fruwirthstrasse 20, Stuttgart, Germany, 70599

3 Universidad Politecnico de Madrid, E.T.S.I. Agronómica, Alimentaria y de Biosistemas Ciudad Universitaria, Madrid, Spain, 28040


Sustainable use of nitrogen (N) fertilizers is essential for agronomic efficiency and environmental stewardship. Nitrification inhibitors (NI) can play an important role in mitigating unwanted environmental impacts by N fertilization, i.e. nitrate leaching and greenhouse gas/N2O emissions, while sustaining and increasing yields. A new nitrification inhibitor 3,4 dimethylpyrazol succinic acid (DMPSA) has been developed characterized by a slower reagent release curve and different physicochemical properties as compared to established inhibitors. In recent years, the new inhibitor was evaluated and tested in laboratory and field trials regarding yields, N uptake and N2O emissions in different environments and combined with varying fertilizers (e.g. urea, CAN) and crops (arable crops, vegetables, fruits). DMPSA was proven applicable to reduce N2O emissions form urea and CAN by 60-90% as compared to the untreated fertilizer. On the tested fertilization levels yields and N-uptake were mainly unaffected or slightly increased by application of DMPSA, on average +4% and +2% for yield and N-uptake, respectively. The effect of DMPSA appeared to be independent of the N fertilizer type combined with the compound and crop type. The application of the new compound could still be further improved by reducing fertilization levels sustaining the same yield and N uptake level and varying fertilizer management by reducing the number of split N applications. Additional options for an optimized fertilizer N management by use of DMPSA require further investigation.

The effect of nitrification inhibitors on wheat crop performance on coarse-grained soils in Mediterranean environments

Elliott Duncan1,2*, Cathryn O’Sullivan1, Margaret Roper1 and Mark Peoples3

 1 CSIRO Agriculture, Centre for Environment and Life Sciences, Underwood Avenue, Floreat WA 6014, Australia.

2 Future Industries Institute, University of South Australia, Mawson Lakes Campus, Mawson Lakes, SA 5095, Australia.

3 CSIRO Agriculture, Black Mountain Laboratories, Acton, ACT 2601, Australia.

Email – Elliott.duncan@unisa.edu.au


This research investigates whether nitrification inhibitors (NIs), including DMPP, DCD & nitrapyrin, are effective in preserving ammonium (NH4+) in soil, reducing the abundance of ammonia oxidising microorganisms in soil and improving crop performance in Mediterranean wheat cropping systems. Data from laboratory soil incubation studies and glasshouse pot trials demonstrated that, under controlled conditions, DMPP was highly effective at inhibiting nitrification and limiting the growth of ammonia oxidising bacteria (AOB) for over 100 days on coarse-grained soils common in the Western Australian wheatbelt. This, however, did not result in improvements in grain yield or quality in wheat (Triticum aestivum) cv. Mace which suggests that preservation of mineral N as NH4+ does little for crop N uptake. Under field conditions yield increases of ≈300 kg ha-1 were observed in the presence of DMPP in a small number of trials. These increases, however, only occurred on soils with a shallow coarse-grained layer (<30cm) over a heavy clay pan. It is likely that the clay layer in these soils slowed the movement of water (and N) thus allowing the crop access to fertiliser N for a longer period of time.  Overall, this study demonstrates that NIs slow nitrification in a range of soils common in the study region and in some cases yield and NUE benefits can occur.

Agronomic evaluation of enhanced efficiency N fertilizers in lowland rice

Dinesh Kumar

Division of Agronomy, ICAR-Indian Agricultural Research Institute, New Delhi 110 012, INDIA, Email: dineshctt@yahoo.com


Nitrogen use efficiency (NUE), expressed as agronomic efficiency, of prilled urea is quite low under lowland rice in India. Among the different strategies used for enhancing agronomic efficiency of fertilizer N, use of enhanced efficiency fertilizers holds a great promise. Therefore a field experiment was conducted at the Research Farm of ICAR-Indian Agricultural Research Institute, New Delhi for two consecutive years. Main objective of the study was to find out the effect of essential and vegetable oils coated prilled urea on grain yield and agronomic efficiency of rice. The treatments (22) comprised of combinations of 3 N rates (50, 100 and 150 kg N/ha) and 7 N sources (citronella oil, meliacins, karanj oil, lemongrass oil, cottonseed oil, palmarosa oil and no oil coated prilled urea) at a thickness of 1000 mg oil/kg urea, and an absolute control. The experiment was laid out in a Randomized Block Design with three replications. Rice grain yield increased significantly up to highest N rate (150 kg/ha). All the oil coated ureas, except palmarosa oil, produced significantly higher rice grain yield over uncoated urea. Citronella oil coated urea produced highest grain yield of rice, being at par to karanj oil and cottonseed oil coated urea, but significantly higher than other coated ureas. The highest agronomic efficiency of nitrogen was recorded with citronella oil coated prilled urea.

The role of nitrification inhibitors and polymer coated urea in N management in the sub-tropics

Terry J Rose1, Lee J Kearney1, Stephen Kimber2, Stephen Morris2, Peter Quin1, Lukas van Zwieten1,2

1 Southern Cross University, Military Road, East Lismore, NSW, 2480, www.scu.edu.au

2 NSW Department of Primary Industries, 1243 Bruxner HWY, Wollongbar, NSW, 2480, www.dpi.nsw.gov.au


While there is a growing body of literature suggesting that the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) can reduce N2O emissions from soils in temperate environments, there is little evidence of its efficacy in subtropical and tropical environments where temperatures and rainfall intensities are typically higher. We investigated N2O emissions in aerobic rice crops in a subtropical environment in late summer/autumn in 2014 and in an adjacent field in late summer/autumn in 2015. Crops received 80 kg/ha N as either urea, DMPP-urea, or a blend of 50 % urea and 50 % urea-DMPP in 2014, and urea, urea-DMPP or polymer-coated urea (PCU) in 2015. DMPP-urea significantly (P < 0.05) lowered soil N2O emissions in the 2013-14 season during the peak flux period after N fertiliser was applied, but had no effect in the 2014-15 season. The mean cumulative N2O emissions over the entire growing period were 190 g N2O-N/ha in 2013-14 and 413 g N2O-N/ha in 2014-15, with no significant effect of DMPP or PCU. Our results demonstrate that DMPP can lower N2O emissions in subtropical, aerobic rice crops during peak flux events following N fertiliser application in some seasons, but inherent variability in soil N2O emissions limit the chances of detecting significant differences in cumulative N2O flux over longer time periods. A greater understanding of how seasonal and/or soil factors impact the efficacy of DMPP in lowering N2O emissions following N fertiliser application in the subtropics is needed to formulate appropriate guidelines for its use commercially.