Polymer Coated Urea: Mitigating Nitrogen Loss to the Environment

Bryan G. Hopkins1

1 Brigham Young University, 5115 LSB, Provo, Utah, 84602, http://lifesciences.byu.edu/~BRYANGH, hopkins@byu.edu


Fertile soil is the foundation for food production and successful civilizations and is developed and maintained through the addition of nutrients lost through harvest. Nitrogen (N) accounts for approximately half of global fertilizer inputs. However, N recovery by plants is inherently inefficient with uptake of applied fertilizer N less than most other nutrients. Losses from the soil system can cause negative air and water resource impacts. Additionally, poor fertilizer efficiency is a waste of natural resources and potentially reduces yields, crop quality, and grower profits. Nitrogen-use efficiency (NUE) is increased through using optimal source, rate, timing, and placement. Polymer coated urea (PCU) is a source of N fertilizer that, when correctly managed, can result in virtually no N loss beyond background levels. A summary of our laboratory, glasshouse, and field research trials shows significantly less N loss from soil to the air and water due to dramatic increases in NUE from PCU compared to uncoated urea. Average ammonia volatilization and nitrous oxide emissions were lower for PUC by 300 and 120%, respectively. Residual nitrate was 38% lower for PCU compared to uncoated urea. The N losses for PCU fertilized plants were at or nearly the same as background levels for the controls.  In all cases, PCU resulted in crop yields and/or quality which were significantly improved or at least equivalent to uncoated urea when managed properly. The global use of PCU is warranted to greatly improve environmental quality and to meet the demands for providing food, fuel, and fiber for the seven billion plus people on earth.

Dynamics of nitrate accumulation in soil as a function of inorganic and organic fertilization

Attila Dunai, Zoltan Toth

University of Pannonia Georgikon Faculty, 16 Deak Ferenc Str, Keszthely, Hungary, H-8360, www.georgikon.hu, dunai@georgikon.hu


The study was carried out in a long-tem field experiment set up in 1983 at the experimental site of the University of Pannonia Georgikon Faculty, Keszthely, Hungary. The experimental factors were the increasing rates of mineral N fertilizer and the complementary applied organic fertilizers (NPK: inorganic fertiilizers only, NPK + FYM: inorganic fertilizers and farmyard manure, NPK + St + GM: inorganic fertilizers, straw and green manure ploughed-in). Soil was a Ramann-type brown forest soil (Eutric Cambisol), with low humus content. The annual precipitation of the year of study was relatively high (877,1 mm).The amount of precipitation in the studied period (May-September 2014) was also high (557,1 mm).

Sampling of nitrate was carried out in the 0-1 m soli layer in 5 sublayers (0-20, 20-40, 40-60, 60-80, 80-100 cm) and in ten different dates during the growing season of corn in 2014.

The results show limited nitrate leaching in the first half of the growing season until a depth of 60 cm. No leaching of NO3was measured in the deep soil layers below 60 cm. By the end of growing season soil became exhausted due to the nitrate absorption of the crop. Additional applied organic fertilizers resulted in higher nitrate values in the 0-60 cm soil layer at the first sampling date compared to the NPK plots, but these values reduced by the end of season without leaching.

Improving nitrogen use efficiency of irrigated rice (Oryza sativa L.): use of Stabilized Urea

Kumara H.G.J.T.1, Nissanka S.P1, Gunawardane M2, Abeysiriwardane D. S. De Z.3

1Department of Crop Science, Faculty of Agriculture, University of Peradeniya, Peradeniya, Sri Lanka. spnissanka@gmail.com

2SLINTEC, Nanotechnology and Science Park, Mahenwatte, Pitipana, Homagama, Sri Lanka

3CIC Agri Businesses (Pvt) Ltd, Pelwehera, Dambulla, Sri Lanka


Agronomic efficiency of N (AEN) in rice cultivation ranges from 20-40 % due to heavy losses of applied N. Dicyandiamide (DCD) and N-(n-butyl) thiophosphorictriamide (NBPT) are used for some crops to enhance the efficiency of urea fertilizer and reduce ammonia volatilization, respectively. The DCD and NBPT were evaluated in combination with different levels of the recommended rate of urea by the Department of Agriculture (DOA), Sri Lanka to examine the (AEN) in irrigated rice (Oryza sativa L.), conducting a pot experiment. As treatments, three levels of urea (100 % (225 kg Urea/ha), 75 % and 50 % of the DOA recommended rate) in the form of urea, and inhibitor compound with four levels (no compound, only NBPT, only DCD and combination of NBPT + DCD) and a control of no urea applied, were arranged in a Completely Randomized Design (CRD) with three replicates. The DCD and NBPT rates were 10 % and 1 % of the amount of urea used, respectively. Results showed that 50 % urea with inhibitors had no significant yield reduction (P>0.05) compared to 100 % urea alone, with a greater AEN. Thus, application of urea with DCD and NBPT lead to a significant reduction in amount of urea application.

Stability of urease inhibitor added to urea

Heitor Cantarella1, Johnny R. Soares1, Rafael M. Sousa1, Rafael Otto2, Cleiton Sequeira3

1 Agronomic Institute of Campinas, Av. Barão de Itapura 1487, Campinas, SP, 13020-902 Brazil, Email: cantarella@iac.sp.gov.br
2 ESALQ-University of São Paulo, Av. Padua Dias, 11, Piracicaba, SP, 13418-900 Brazil.
3 Koch Agronomic Services, 4111 E. 37th St. N, Wichita, KS 67220, USA.


The urease inhibitor N-(n-butyl thiophosphoric acid triamide) (NBPT) is being used to reduce ammonia (NH3) volatilization losses of surface-applied urea but its shelf life is an issue. Urea treated with NBPT was stored for up to one year at two locations in Brazil: Paranaguá, PR (25°30’S and 48°30’W) and Rondonópolis, MT (16°26’ S and 54°49’ W). Treated urea samples were collected for the determination of NBPT concentration and for NH3 volatilization from a Latosol under laboratory conditions. Ammonia losses from untreated urea varied from 32 to 48% of applied nitrogen (N); the corresponding values for freshly NBPT-treated urea varied from 8 to 26% of applied N. For fertilizer stored up to 6 months, NH3 losses from untreated urea were significantly higher than those of urea containing NBPT, with no difference found among NBPT treated urea samples regardless of storage site and bag size. After 6 months, volatilization losses of NBPT treated samples stored in Rondonópolis were higher than those from Paranaguá. When samples were stored for 9 months, NH3 losses for Paranaguá samples and freshly NBPT-treated urea were about 15% of applied N, while for Rondonópolis samples, losses were about 30% of applied N. Losses for untreated urea were about 45% of applied N. After 1 year, Paranaguá samples were still performing the same as freshly NBPT-treated urea. The degree of degradation of NBPT on urea stored under conditions similar to those of Paranaguá grants a shelf-life longer than those stored under hotter conditions similar to Rondonópolis.

Understanding the variability in performance of the nitrification inhibitor 3,4-Dimethylpyrazole phosphate in Australian agricultural soils

Helen Suter1, Charlie Walker2, Deli Chen1

1 Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Burnley Campus, 500 Yarra Boulevard, Richmond, Victoria 3121, http://fvas.unimelb.edu.au/ Email: helencs@unimelb.edu.au

2 Incitec Pivot Fertilisers, PO Box 54, North Geelong, Victoria 3215, Australia


The nitrification inhibitor 3,4-Dimethylpyrazole phosphate (DMPP) is being widely used across Australian agricultural systems to reduce nitrogen loss from soils, particularly targeting the greenhouse gas nitrous oxide, and to improve nitrogen use efficiency. However, the effectiveness of DMPP is variable and the reason for this has been unclear. A laboratory investigation was undertaken using 30 soils collected from a range of agricultural land uses to identify the key drivers influencing the performance of DMPP. Average nitrification over 14 days across all treatments ranged from -4.61 to 26.89, with a median of 2.57 mg NO3N produced/g soil/day. Cumulative N2O emissions ranged from 0.01 to 7.74 mg N2O-N/g soil. However only 3 soils contributed to high emissions and the remaining soils had < 0.63 mg N2O-N/g soil. DMPP effectively reduced average nitrification by 9-100% (average of 42%) and N2O emissions by 0-100% (average of 55%) Only manganese and the interaction between organic C and clay influenced DMPP’s efficacy at reducing nitrification, having a negative impact. The efficacy of DMPP at inhibiting N2O emissions was positively related to pH, Cu and Zn and negatively related to Fe. The results suggest that further investigation of the soil metal-inhibitor interaction, and the role of metals in soil microbial function (nitrifiers and denitrifiers) is required to understand when the DMPP will work best.

Effect of a new urease inhibitor on ammonia volatilization and nitrogen utilization in maize in North China Plain

Li Qianqian1, Liu Xuejun1, Chen Xinping1, Zhang Fusuo1

1 College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, website: http://www.cau.edu.cn/, Email: lilli@cau.edu.cn; liu310@cau.edu.cn


Maize field experiments were conducted over two years at Quzhou site (Hebei Province, North China Plain) to investigate ammonia (NH3) volatilization from urea and from urea amended with 0.12% (w/w) Limus® (a new urease inhibitor). Grain yields and nitrogen (N) budgets of all N treatments were evaluated to investigate the effects of urea-N application rates and Limus during two summer maize seasons. Cumulative NH3 losses after two weeks for conventional urea ranged from 42 to 108 kg N ha-1 (20-57% of applied N), while the new urease inhibitor Limus significantly reduced NH3 losses by 65 to 90%. However, maize grain yields (9.5-10.1 t ha-1) were not significantly (P<0.05) increased by Limus compared to conventional urea without Limus (9.0-10.1 t ha-1). A clear increase in apparent N recovery efficiency (REN) with Limus (ranging from 11 to 17 percentage points during two consecutive maize seasons) compared to equal amounts of optimized urea-N. A further 20% reduction in urea N rate amended with Limus led to the same maize yield but substantially decreased NH3 losses and increased REN compared with optimized urea treatment. Our study also demonstrates the role of Limus in reducing NH3 losses and improving N use efficiency in maize production in the North China Plain.

Improving nitrogen efficiency of maize (corn) using crop sensors

Peter Scharf 1

1 University of Missouri, 108 Waters Hall, Columbia, MO, 65211, U.S.A., http://plantsci.missouri.edu/nutrientmanagement/, http://nvisionag.com/, scharfp@missouri.edu


Nitrogen fertilizer has a tremendous impact on crop growth and is essential for feeding the 7.4 billion people on Earth.  It is also the most energy-intensive input to crop agriculture, has a proclivity to escape from ag systems, and has negative off-site impacts when it escapes.  For all of these reasons, efficient use of N fertilizer is essential.  Crop sensors are a promising approach to optimize N fertilizer application rate and timing.  Three separate experiments with maize (corn) helped to define the N efficiency gains to this approach.  One experiment group involved 55 field-scale experiments in which the farmer’s N rate was compared to variable-rate N based on crop sensors.  System efficiency (N removed in grain/[N applied as fertilizer + manure]) was 0.68 with the farmer’s chosen rate, and increased to 0.78 with sensor-chosen N rates.  A second experiment was initiated in 2007 to compare N fertilizer rate and timing decision systems.  For 2007-2014, the most profitable pre-plant N rate (200 kg N ha-1) gave system N efficiency of 0.43, while sensor-based N rate gave system N efficiency of 0.74. The third experiment was initiated in 2012 and compared a pre-plant N rate of 155 kg N ha-1 with sensor-based variable-rate N.  System efficiency for pre-plant N was 0.51, and for sensor-based N was 0.57.  In the latter two experiments, pre-plant N treatments had low efficiency in years with high spring rainfall.  Timing of N probably improved N efficiency more than improved N rate.

Assessing controlled release and deep placement N fertilizer technologies in subtropical sugarcane

Lukas Van Zwieten1,2, Josh Rust1, Terry J Rose2, Stephen Joseph3, Rick Beattie4, Scott Donne3, Greg Butler5, Robert Quirk6, Stephen Kimber1, Stephen Morris1

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

2 Southern Cross Plant Science, Southern Cross University, Military Road, East Lismore, NSW, 2480

3 Discipline of Chemistry, University of Newcastle, Callaghan NSW 2308

4 Sunshine Sugar, Suite 1, Level 1, Cnr River and Martin Streets Ballina, NSW, 2478

5 South Australia No-Till Farmers Association, PO Box 930 Berri, SA,5343

6 30 Duranbah Road, Duranbah, NSW 2487


Maintaining adequate nitrogen (N) nutrition in sugarcane requires matching supply with demand. The NSW sugarcane system predominantly grows sugarcane over 2 years, with fertiliser N supplied within a couple of months after planting cane or harvesting the previous crop and ratooning. We evaluated alternate N fertiliser technologies; a) that supply N deeper into the soil profile (ca. 50-200mm) via ultra-high pressure, and b) slow release products. Preliminary results indicate that polymer coated urea is able to lower nitrous oxide (N2O) emissions during peak events, presumable by limiting mineral N in soil at any given time. This lower soil NO3 was observed at site 1 in the 2015/16 season only. The N fertiliser based on a modified charcoal pellet gave lower cumulative N2O emissions than farmer practice urea (matching N rate) at only one of six field sites. The emissions of N2O did not appear to depend upon the dose of fertiliser N applied, but were site specific, and highly dependent upon rainfall events.

Controlled release nitrogen fertilizer use in potato production systems of eastern Canada

Noura Ziadi1, Mervin St.Luce1, Athyna N. Cambouris1, and Bernie J. Zebarth2

1Agriculture and Agri-Food Canada, 2560 Hochelaga Blvd, Quebec, QC, Canada, G1V 2J3, Noura.Ziadi@agr.gc.ca

2Agriculture and Agri-Food Canada, PO Box 20280, 850 Lincoln Rd., Fredericton, NB, Canada E3B 4Z7


Nitrogen (N) is the most limiting essential nutrient for potato (Solanum tuberosum L.) and its management is important from both economic and environmental standpoints. Controlled-release N fertilizers, such as polymer-coated urea (PCU), could reduce N losses and increase N use efficiency (NUE) by matching the release of N with potato N uptake. During the last 10 years, different studies were conducted in eastern Canada (Quebec and New-Brunswick) to evaluate the effectiveness of PCU in potato production. A total of nine site-years were conducted between 2006 and 2012 to compare the PCU to the most used conventional N sources. Their effects were assessed on various parameters including yield, specific gravity, NUE, chlorophyll meter readings nitrate (NO3) leaching, and nitrous oxide (N2O) emissions along with soil nitrate availability during growing seasons and at harvest. Our results showed that PCU can maintain or increase marketable tuber yield and quality, increase NUE, and reduce NO3 leaching, particularly in excessively wet years. However, higher N availability from PCU may have implications for N2O emissions and non-growing season N losses. Evidence of the overall economic advantages of using the PCU in potato production, if any, will be needed to influence a more widespread adoption of PCU by producers.

Effects of polymer- and nitrification inhibitor-coated urea on N2O emission, productivity and profitability in a wet tropical sugarcane crop in Australia

Weijin Wang1,2, Lawrence Di Bella3, Steven Reeves1, Melissa Royle3, Marijke Heenan1, Minka Ibanez3

1 Department of Science, Information Technology and Innovation, 41 Boggo Road, Dutton Park QLD 4102, Australia; Email: weijin.wang@qld.gov.au

2 Environmental Futures Research Institute, Griffith University, Nathan, QLD 4111, Australia

3 Herbert Cane Productivity Services Limited, 181 Fairford Rd, Ingham, QLD 4850, Australia


Sugarcane crops are predominantly grown in warm and high rainfall or irrigated areas where substantial fertiliser nitrogen (N) losses can occur. This study was conducted in a wet tropical sugarcane cropping system to assess polymer-coated urea (PCU), polymer- and sulphur-coated urea (PSCU) and the denitrification inhibitor DMPP-coated urea (NICU) on sugar productivity, N use efficiency and profitability at the normal application rate (150 kg N/ha) and a reduced rate (110 kg N/ha). Nitrous oxide (N2O) emissions were also measured for selected treatments using automatic and manual gas sampling chambers in combination. The results demonstrated that annual cumulative N2O emissions in the treatment receiving conventional urea at 150 kg N/ha amounted to 4.74 and 9.51 kg N2O-N/ha, with the fertiliser N emission factor of 1.90 and 3.01%, based on the manual and automatic chamber measurements, respectively. Application of NICU decreased the annual fertiliser-induced N2O emission by approximately 83%. However, N2O emissions in the PSCU treatment were about two times that in the conventional urea treatment, probably due to less N leaching from PSCU. Use of PCU, PSCU and NICU at 150 kg N/ha increased the sugar yield by 2.5, 3.3 and 2.8 t/ha, respectively, compared to the conventional urea treatment (8.4 t/ha). The crop N uptake in the aboveground biomass were significantly higher for the coated urea fertilisers than uncoated urea, and higher for PSCU and NICU than PCU at 150 kg N/ha. The farming profits also tended to be higher for the coated urea fertilisers than the conventional urea.