Register      Login
Soil Research Soil Research Society
Soil, land care and environmental research
REVIEW (Open Access)

Enhanced nitrogen fertiliser technologies support the ‘4R’ concept to optimise crop production and minimise environmental losses

Clifford S. Snyder
+ Author Affiliations
- Author Affiliations

International Plant Nutrition Institute, PO Box 10509, Conway, AR 72034, USA. Email: csnyder@ipni.net

Soil Research 55(6) 463-472 https://doi.org/10.1071/SR16335
Submitted: 18 January 2017  Accepted: 2 May 2017   Published: 2 June 2017

Journal Compilation © CSIRO Publishing 2017 Open Access CC BY-NC-ND

Abstract

Fertiliser nitrogen (N) has been, and will continue to be, essential in nourishing, clothing and providing bioenergy for the human family. Yet, emissions of ammonia (NH3) and nitrous oxide (N2O), and losses of nitrate-N (NO3-N) to surface and groundwater resources are risks associated with fertiliser N use that must be better managed to help meet expanding societal expectations. Nitrogen fertilisers with polymer coatings, or with the addition of urease and/or nitrification inhibitors, or those possessing other characteristics that afford them either improved agronomic response and/or lessened loss of N to the environment (compared with a reference water-soluble fertiliser) may be considered enhanced-efficiency N fertilisers (EEFs). Agronomic and horticultural research with these technologies has been performed for many decades, but it has been primarily in the past decade that research has increasingly also measured their efficacy in reducing N losses via volatilisation, leaching, drainage, run-off and denitrification. Expanded use of EEFs, within the ‘4R’ concept (right source, right rate, right time, right place) of N management may help increase crop yields while minimising environmental N losses. Coupling these 4R N management tools with precision technologies, information systems, crop growth and N utilisation and transformation models, especially weather models, may improve opportunities for refined N management in the future.

Additional keywords: climate smart agriculture, crop yield, economics, nitrogen recovery, sustainability.


References

Abalos D, Jeffery S, Sanz-Cobena A, Guardia G, Vallejo A (2014) Meta-analysis of the effect of urease and nitrification inhibitors on crop productivity and nitrogen use efficiency. Agriculture, Ecosystems & Environment 189, 136–144.
Meta-analysis of the effect of urease and nitrification inhibitors on crop productivity and nitrogen use efficiency.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2cXnslGqs7Y%3D&md5=35de10a19b954afb81e1ae6701ede5d5CAS |

Bramley R, Trengrove S (2013) Precision agriculture in Australia: present status and recent developments. Engenharia Agrícola 33, 575–588.
Precision agriculture in Australia: present status and recent developments.Crossref | GoogleScholarGoogle Scholar |

Bruulsema T, Lemunyon J, Herz B (2009) Know your fertilizer rights. Crops and Soils 42, 13–18.

Burzaco JP, Smith DR, Vyn TJ (2013) Nitrous oxide emissions in Midwest US maize production vary widely with band-injected N fertilizer rates, timing and nitrapyrin presence. Environmental Research Letters 8, 035031

Burzaco JP, Ciampitti IA, Vyn TJ (2014) Nitrapyrin impacts on maize yield and nitrogen use efficiency with spring-applied nitrogen: field studies vs. meta-analysis comparison. Agronomy Journal 106, 753–760.
Nitrapyrin impacts on maize yield and nitrogen use efficiency with spring-applied nitrogen: field studies vs. meta-analysis comparison.Crossref | GoogleScholarGoogle Scholar |

Butchee KS, May J, Arnall B (2011) Sensor based nitrogen management reduced nitrogen and maintained yield. Crop Management 10,
Sensor based nitrogen management reduced nitrogen and maintained yield.Crossref | GoogleScholarGoogle Scholar |

Cameron KC, Di HJ, Moir JL (2013) Nitrogen losses from the soil/plant system: a review. Annals of Applied Biology 162, 145–173.
Nitrogen losses from the soil/plant system: a review.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3sXntVagsr4%3D&md5=e97e9422aa77986d7e708a2c9fce52f2CAS |

Cassman KG, Dobermann A, Walters DT, Yang H (2003) Meeting cereal demand while protecting natural resources and improving environmental quality. Annual Review of Environment and Resources 28, 315–358.
Meeting cereal demand while protecting natural resources and improving environmental quality.Crossref | GoogleScholarGoogle Scholar |

Chien SH, Edmeades D, McBride R, Sahrawat KL (2014) Review of maleic–itaconic acid copolymer purported as urease inhibitor and phosphorus enhancer in soils. Agronomy Journal 106, 423–430.
Review of maleic–itaconic acid copolymer purported as urease inhibitor and phosphorus enhancer in soils.Crossref | GoogleScholarGoogle Scholar |

Chikowo R, Corbeels M, Mapfumo P, Tittonell P, Vanlauwe B, Giller KE (2010) Nitrogen and phosphorus capture and recovery efficiencies, and crop responses to a range of soil fertility management strategies in sub-Saharan Africa. Nutrient Cycling in Agroecosystems 88, 59–77.
Nitrogen and phosphorus capture and recovery efficiencies, and crop responses to a range of soil fertility management strategies in sub-Saharan Africa.Crossref | GoogleScholarGoogle Scholar |

Dalal RC, Wang W, Robertson GP, Parton WJ (2003) Nitrous oxide emission from Australian agricultural lands and mitigation options; a review. Australian Journal of Soil Research 41, 165–195.
Nitrous oxide emission from Australian agricultural lands and mitigation options; a review.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD3sXktFKisr8%3D&md5=bff5ee383b9e355dc5e24bbaa36e4329CAS |

De Antoni Migliorati M, Scheer C, Grace PR, Rowlings DW, Bell M, McGree J (2014) Influence of different nitrogen rates and DMPP nitrification inhibitor on annual N2O emissions from a subtropical wheat–maize cropping system. Agriculture, Ecosystems & Environment 186, 33–43.
Influence of different nitrogen rates and DMPP nitrification inhibitor on annual N2O emissions from a subtropical wheat–maize cropping system.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2cXmsVCjtbo%3D&md5=298ba597815f209035f442e1f0cbc94aCAS |

Del Grosso SJ, White JW, Wilson G, Vandenberg B, Karlen DL, Follett RF, Johnson JMF, Franzluebbers AJ, Archer DW, Gollany HT, Liebig MA, Ascough J, Reyes-Fox M, Pellack L, Starr J, Barbour N, Polumsky RW, Gutwein M, James D (2013) Introducing the GRACEnet/REAP data contribution, discovery, and retrieval system. Journal of Environmental Quality 42, 1274–1280.
Introducing the GRACEnet/REAP data contribution, discovery, and retrieval system.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3sXhtFOjsLrJ&md5=5ed87d798f51daccbcabfb82f84f54c5CAS |

Dourado-Neto D, Powlson D, Abu Bakar R, Bacchi OOS, Basanta MV, thi Cong P, Keerthisinghe G, Ismaili M, Rahman SM, Reichardt K, Safwat MSA, Sangakkara R, Timm LC, Wang J, Zagal E, van Kessel C (2010) Multiseason recoveries of organic and inorganic nitrogen-15 in tropical cropping systems. Soil Science Society of America Journal 74, 139–152.

Fernández FG, Terry RE, Coronel EG (2015) Nitrous oxide emissions from anhydrous ammonia, urea, and polymer-coated urea in Illinois cornfields. Journal of Environmental Quality 44, 415–422.
Nitrous oxide emissions from anhydrous ammonia, urea, and polymer-coated urea in Illinois cornfields.Crossref | GoogleScholarGoogle Scholar |

Fixen P, Brentrup F, Bruulsema T, Garcia F, Norton R, Zingore S (2015) Nutrient/fertilizer use efficiency: measurement, current situation and trends. In ‘Managing water and fertilizer for sustainable agricultural intensification’. (Eds P Drechsel, P Heffer, H Magen, R Mikkelsen, D Wichelns) pp. 8–38. (International Fertilizer Industry Association, International Water Management Institute, International Plant Nutrition Institute, and International Potash Institute (IPI): Paris, France)

Flynn HC, Smith P (2010) ‘Greenhouse gas budgets of crop production – current and likely future trends.’ 1st edn. (International Fertilizer Industry Association: Paris, France). Available at https://www.researchgate.net/publication/49466090_Greenhouse_gas_budgets_of_crop_production_current_and_likely_future_trends [verified 10 May 2016].

Franzen DR, Goos J, Norman RJ, Walker TW, Roberts TL, Slaton NA, Endres G, Ashley R, Staricka J, Lukach J (2011) Field and laboratory studies comparing nutrisphere-nitrogen urea with urea in North Dakota, Arkansas, and Mississippi. Journal of Plant Nutrition 34, 1198–1222.
Field and laboratory studies comparing nutrisphere-nitrogen urea with urea in North Dakota, Arkansas, and Mississippi.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXlvFGgt7o%3D&md5=66838b2e373b16296dab945a88a6b8dfCAS |

Freney JR (1997) Emission of nitrous oxide from soils used for agriculture. Nutrient Cycling in Agroecosystems 49, 1–6.
Emission of nitrous oxide from soils used for agriculture.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DyaK2sXmslCqs7k%3D&md5=feaadb29d23446c8723b84ff4ace4470CAS |

Gagnon B, Ziadi N, Grant C (2012) Urea fertilizer forms affect grain corn yield and nitrogen use efficiency. Canadian Journal of Soil Science 92, 341–351.
Urea fertilizer forms affect grain corn yield and nitrogen use efficiency.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38Xms1Sqtrw%3D&md5=0eeec841bffeb07ce0de8ab60bb48d48CAS |

Gao X, Asgedom H, Tenuta M, Flaten DN (2015) Enhanced efficiency urea sources and placement effects on nitrous oxide emissions. Agronomy Journal 107, 265–277.
Enhanced efficiency urea sources and placement effects on nitrous oxide emissions.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2MXhtlaisr0%3D&md5=14770bd9664c71293713b1cd4f0e0b01CAS |

Golden B, Slaton N, Norman R, Gbur E, Wilson C (2011) Nitrogen release from environmentally smart nitrogen fertilizer as influenced by soil series, temperature, moisture, and incubation method. Communications in Soil Science and Plant Analysis 42, 1809–1824.
Nitrogen release from environmentally smart nitrogen fertilizer as influenced by soil series, temperature, moisture, and incubation method.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXptFCrtb0%3D&md5=3553e720eb3e91b32edb184dfa896263CAS |

Global Partnership on Nutrient Management (GPNM) (2014) The Global Partnership on Nutrient Management (GPNM) fact sheet. United Nations Environment Programme, Global Programme of Action for the Protection of the Marine Environment from Land-Based Activities. Available at https://wedocs.unep.org/bitstream/handle/20.500.11822/11996/GPNMRevisedDecember2014.pdf?sequence=1&isAllowed=y [verified 14 May 2017].

Grace PR (2016) Foreword to ‘Nitrous oxides in soils’. Australian Journal of Soil Research 54, i–ii.
Foreword to ‘Nitrous oxides in soils’.Crossref | GoogleScholarGoogle Scholar |

Grant C (2005) Policy aspects related to the use of enhanced-efficiency fertilizers: viewpoint of the scientific community. In ‘IFA International Workshop on Enhanced-Efficiency Fertilizers’, 28–30 June 2005, Frankfurt, Germany. (Ed. C Watson) pp. 1–11. (International Fertilizer Industry Association: Paris, France)

Halvorson AD, Snyder CS, Blaylock AD, Del Grosso SJ (2014) Enhanced-efficiency nitrogen fertilizers: potential role in nitrous oxide emission mitigation. Agronomy Journal 106, 715–722.
Enhanced-efficiency nitrogen fertilizers: potential role in nitrous oxide emission mitigation.Crossref | GoogleScholarGoogle Scholar |

Harris RH, Armstrong RD, Wallace AJ, Belyaeva ON (2016) Effect of nitrogen fertiliser management on soil mineral nitrogen, nitrous oxide losses, yield and nitrogen uptake of wheat growing in waterlogging-prone soils of south-eastern Australia. Australian Journal of Soil Research 54, 619–633.
Effect of nitrogen fertiliser management on soil mineral nitrogen, nitrous oxide losses, yield and nitrogen uptake of wheat growing in waterlogging-prone soils of south-eastern Australia.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC28XhtlejtL%2FF&md5=950a5de7a6d2768bda6e2bf974910497CAS |

Hatfield JL, Venterea RT (2014) Enhanced efficiency fertilizers: a multi-site comparison of the effects on nitrous oxide emissions and agronomic performance. Agronomy Journal 106, 1–2.
Enhanced efficiency fertilizers: a multi-site comparison of the effects on nitrous oxide emissions and agronomic performance.Crossref | GoogleScholarGoogle Scholar |

Hong N, Scharf PC, Davis JG, Kitchen NR, Sudduth KA (2007) Economically optimum nitrogen rate reduces residual soil nitrate. Journal of Environmental Quality 36, 354–362.
Economically optimum nitrogen rate reduces residual soil nitrate.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2sXjsV2jsrc%3D&md5=d5fc8e4a9e364d5a71bc8ebc90619514CAS |

Hyatt CR, Venterea RT, Rosen CJ, McNearney M, Wilson ML, Dolan MS (2010) Polymer-coated urea maintains potato yields and reduces nitrous oxide emissions in a Minnesota loamy sand. Soil Science Society of America Journal 74, 419–428.
Polymer-coated urea maintains potato yields and reduces nitrous oxide emissions in a Minnesota loamy sand.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXjtFWrtLY%3D&md5=67016e2c53dccf4c5671fb17aad1b671CAS |

International Fertilizer Industry Association (IFA) (2009a) The global ‘4R’ nutrient stewardship framework: developing fertilizer best management practices for delivering economic, social and environmental benefits. IFA: Paris, France. Available at http://www.fertilizer.org//en/ItemDetail?iProductCode=9677Pdf&Category=AGRI [verified 10 May 2016].

International Fertilizer Industry Association (IFA) (2009b) Fertilizers, climate change and enhancing agricultural productivity sustainably. IFA: Paris, France.

International Plant Nutrition Institute (IPNI) (2012) ‘4R plant nutrition manual: a manual for improving the management of plant nutrition, metric version.’ (Eds TW Bruulsema, PE Fixen, GD Sulewski). (IPNI: Norcross, GA)

Jamali H, Quayle W, Scheer C, Baldock J (2016) Mitigation of N2O emissions from surface-irrigated cropping systems using water management and the nitrification inhibitor DMPP. Australian Journal of Soil Research 54, 481–493.
Mitigation of N2O emissions from surface-irrigated cropping systems using water management and the nitrification inhibitor DMPP.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC28XhtlejtL%2FJ&md5=7a2d355db1d4353750d2d160d939baf2CAS |

Johnston AM, Bruulsema TW (2014) 4R nutrient stewardship for improved nutrient use efficiency. Procedia Engineering 83, 365–370.
4R nutrient stewardship for improved nutrient use efficiency.Crossref | GoogleScholarGoogle Scholar |

Lam SK, Chen D, Norton R, Armstrong R, Mosier AR (2012) Nitrogen dynamics in grain crop and legume pasture systems under elevated atmospheric carbon dioxide concentration: a meta-analysis. Global Change Biology 18, 2853–2859.
Nitrogen dynamics in grain crop and legume pasture systems under elevated atmospheric carbon dioxide concentration: a meta-analysis.Crossref | GoogleScholarGoogle Scholar |

Lam SK, Suter H, Davies R, Bai M, Sun J, Chen D (2015) Measurement and mitigation of nitrous oxide emissions from a high nitrogen input vegetable system. Scientific Reports 5, 1–4.
Measurement and mitigation of nitrous oxide emissions from a high nitrogen input vegetable system.Crossref | GoogleScholarGoogle Scholar |

Lam SK, Suter H, Mosier AR, Chen D (2016) Using nitrification inhibitors to mitigate agricultural N2O emission: a double-edged sword? Global Change Biology 18, 2853–2859.
Using nitrification inhibitors to mitigate agricultural N2O emission: a double-edged sword?Crossref | GoogleScholarGoogle Scholar |

Landels SP (2010) Enhanced-efficiency fertilizers: world market overview. In ‘International Conference on Enhanced-Efficiency Fertilizers – an IFA-New Ag international event’, 23–24 March 2010, Miami, FL. Available at http://www.fertilizer.org/ItemDetail?iProductCode=9029Pdf&Category=ECO&WebsiteKey=411e9724-4bda-422f-abfc-8152ed74f306 [verified 10 May 2016].

Lester DW, Bell MJ, Bell KL, De Antoni Migliorati M, Scheer C, Rowlings D, Grace PR (2016) Agronomic responses of grain sorghum to DMPP-treated urea on contrasting soil types in north-eastern Australia. Australian Journal of Soil Research 54, 565–571.
Agronomic responses of grain sorghum to DMPP-treated urea on contrasting soil types in north-eastern Australia.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC28XhtlejtL%2FN&md5=23857599358990b134710603f025d2c5CAS |

Li A, Duval BD, Anex R, Scharf P, Ashtekar JM, Owens PR, Ellis C (2016) A case study of environmental benefits of sensor-based nitrogen application in corn. Journal of Environmental Quality 45, 675–683.
A case study of environmental benefits of sensor-based nitrogen application in corn.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC28XpsV2hur4%3D&md5=8e31c6164cdf2bda252cc9ee44372f20CAS |

Linquist BA, Liu L, van Kessel C, van Groenigen KJ (2013) Enhanced efficiency nitrogen fertilizers for rice systems: meta-analysis of yield and nitrogen uptake. Field Crops Research 154, 246–254.
Enhanced efficiency nitrogen fertilizers for rice systems: meta-analysis of yield and nitrogen uptake.Crossref | GoogleScholarGoogle Scholar |

Maharjan B, Venterea RT, Rosen C (2014) Fertilizer and irrigation management effects on nitrous oxide emissions and nitrate leaching. Agronomy Journal 106, 703–714.
Fertilizer and irrigation management effects on nitrous oxide emissions and nitrate leaching.Crossref | GoogleScholarGoogle Scholar |

Maharjan B, Ferguson RB, Slater GP (2016) Polymer-coated urea improved corn response compared to urea–ammonium–nitrate when applied on a coarse-textured soil. Agronomy Journal 108, 509–518.
Polymer-coated urea improved corn response compared to urea–ammonium–nitrate when applied on a coarse-textured soil.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC28Xhtl2jsLrI&md5=dec031f3ec392e8491d4615c8e1c7c69CAS |

McIsaac GF, David MB, Gertner GZ (2016) Illinois River nitrate-nitrogen concentrations and loads: long-term variation and association with watershed nitrogen inputs. Journal of Environmental Quality 45, 1268–1275.
Illinois River nitrate-nitrogen concentrations and loads: long-term variation and association with watershed nitrogen inputs.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2sXhs1Oqu7k%3D&md5=5a0b690018109884a8f2930f3cf6128cCAS |

Mueller ND, Gerber JS, Johnston M, Ray DK, Ramankutty N, Foley JA (2012) Closing yield gaps through nutrient and water management. Nature 490, 254–257.
Closing yield gaps through nutrient and water management.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38Xht1Kku7vI&md5=9d06d4e94d4c34e3823fdac51e604781CAS |

Mulla D (2016) Comparison of real-time N stress sensors and remote sensing from unmanned aerial vehicles for precision management of N fertilizer and improvement of water quality. Available at http://www.mda.state.mn.us/protecting/ cleanwaterfund/research/remotesensing.aspx [verified 10 May 2016].

Nash PR, Motavalli PP, Nelson KA (2012) Nitrous oxide emissions from claypan soils due to nitrogen fertilizer source and tillage/fertilizer placement practices. Soil Science Society of America Journal 76, 983–993.
Nitrous oxide emissions from claypan soils due to nitrogen fertilizer source and tillage/fertilizer placement practices.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38XosFeju78%3D&md5=5a2edb4c530c4e22e6cd017a10edf690CAS |

Nash PR, Nelson KA, Motavalli PP (2014) Reducing nitrogen loss in subsurface tile drainage water with managed drainage and polymer-coated urea in a river bottom soil. Journal of Water Resource and Protection 6, 988–997.
Reducing nitrogen loss in subsurface tile drainage water with managed drainage and polymer-coated urea in a river bottom soil.Crossref | GoogleScholarGoogle Scholar |

Nelson KA, Motavalli PP (2013) Nitrogen source, drainage, and irrigation affects corn yield response in a claypan soil. Applied Engineering in Agriculture 29, 875–884.
Nitrogen source, drainage, and irrigation affects corn yield response in a claypan soil.Crossref | GoogleScholarGoogle Scholar |

Nelson KA, Motavalli PP, Dudenhoeffer CJ (2014) Cropping system affects polymer-coated urea release and corn yield response in claypan soils. Journal of Agronomy & Crop Science 200, 54–65.
Cropping system affects polymer-coated urea release and corn yield response in claypan soils.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2cXjtVCnsA%3D%3D&md5=4c43e0291f0d7ffec306dd4d0dc7e6d6CAS |

Norton R (2013) 4R Canola Nutrition Guide – Canola technology update for growers and advisers: nutrient management (V1: Mar 2013). International Plant Nutrition Institute: Norcross, GA. Available at https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwiw-sPCxPDTAhVNziYKHaZUAHgQFggpMAA&url=http%3A%2F%2Fanz.ipni.net%2Fbeagle%2FANZ-3176%26f%3DCanola%25204R%2520Guide.pdf&usg=AFQjCNEwGNhDfGvdsdzziOud8JfS0pHzIQ [verified 14 May 2017].

Norton R, Bruulsema T, Roberts T, Snyder C (2015) Crop nutrient performance indicators. Agricultural Science 27, 33–38.

Pan B, Lam SK, Mosier AR, Luo Y, Chen D (2016) Ammonia volatilization from synthetic fertilizers and its mitigation strategies: a global synthesis. Agriculture, Ecosystems & Environment 232, 283–289.
Ammonia volatilization from synthetic fertilizers and its mitigation strategies: a global synthesis.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC28XhtlKqs7%2FI&md5=9f3d712170c741aa827b7c225ab0b161CAS |

Payne J, Nafziger E (2015) Nitrogen management in Illinois intensifies as state implements nutrient loss reduction strategy. Better Crops with Plant Food 99, 4–6.

Pereira EI, da Cruz CCT, Solomon A, Le A, Cavigelli MA, Ribeiro C (2015) Novel slow-release nanocomposite nitrogen fertilizers: the impact of polymers on nanocomposite properties and function. Industrial & Engineering Chemistry Research 54, 3717–3725.
Novel slow-release nanocomposite nitrogen fertilizers: the impact of polymers on nanocomposite properties and function.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2MXkvVOksLk%3D&md5=60d481a1269412bf98a81e8c9a3d0bedCAS |

Perry EM, Fitzgerald GJ, Nuttall JG, O’Leary GJ, Schulthess U, Whitlock A (2012) Rapid estimation of canopy nitrogen of cereal crops at paddock scale using a canopy chlorophyll content index. Field Crops Research 134, 158–164.
Rapid estimation of canopy nitrogen of cereal crops at paddock scale using a canopy chlorophyll content index.Crossref | GoogleScholarGoogle Scholar |

Powlson DS, Jenkinson DS, Johnston AE, Poulton PR, Glendining MJ, Goulding KWT (2010) Comments on ‘Synthetic nitrogen fertilizers deplete soil nitrogen: a global dilemma for sustainable cereal production,’ by R.L. Mulvaney, S.A. Khan, and T.R. Ellsworth in the Journal of Environmental Quality 2009 38:2295–2314. Journal of Environmental Quality 39, 749–752.
Comments on ‘Synthetic nitrogen fertilizers deplete soil nitrogen: a global dilemma for sustainable cereal production,’ by R.L. Mulvaney, S.A. Khan, and T.R. Ellsworth in the Journal of Environmental Quality 2009 38:2295–2314.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXjsFGjsrk%3D&md5=0aedafce27466362233e9f5dd51c7c38CAS |

Powlson DS, Whitmore AP, Goulding WT (2011) Soil carbon sequestration to mitigate climate change: a critical re-examination to identify the true and the false. European Journal of Soil Science 62, 42–55.
Soil carbon sequestration to mitigate climate change: a critical re-examination to identify the true and the false.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXisVGgtrk%3D&md5=b6c426cb83d9f4bded67a138cc082532CAS |

Qiao C, Liu L, Hu S, Compton JE, Greaver TL, Li Q (2015) How inhibiting nitrification affects nitrogen cycle and reduces environmental impacts of anthropogenic nitrogen input. Global Change Biology 21, 1249–1257.
How inhibiting nitrification affects nitrogen cycle and reduces environmental impacts of anthropogenic nitrogen input.Crossref | GoogleScholarGoogle Scholar |

Quemada M, Baranski M, Nobel-de Lange MNJ, Vallejoa A, Cooper JM (2013) Meta-analysis of strategies to control nitrate leaching in irrigated agricultural systems and their effects on crop yield. Agriculture, Ecosystems & Environment 174, 1–10.
Meta-analysis of strategies to control nitrate leaching in irrigated agricultural systems and their effects on crop yield.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3sXpvVygtro%3D&md5=0f64e32595370c602be0f2ce332cd90bCAS |

Roberts DF, Kitchen NR, Scharf PC, Sudduth KA (2010) Will variable-rate nitrogen fertilization using corn canopy reflectance sensing deliver environmental benefits? Agronomy Journal 102, 85–95.
Will variable-rate nitrogen fertilization using corn canopy reflectance sensing deliver environmental benefits?Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3cXhvFSktbs%3D&md5=10a0b4b67c0111f2240458377b283b3fCAS |

Robertson GP, Vitousek PM (2009) Nitrogen in agriculture: balancing the cost of an essential resource. Annual Review of Environment and Resources 34, 97–125.
Nitrogen in agriculture: balancing the cost of an essential resource.Crossref | GoogleScholarGoogle Scholar |

Robertson MJ, Llewellyn RS, Mandel R, Lawes R, Bramley RGV, Swift L, Metz N, O’Callaghan CO (2012) Adoption of variable rate fertiliser application in the Australian grains industry: status, issues and prospects. Precision Agriculture 13, 181–199.
Adoption of variable rate fertiliser application in the Australian grains industry: status, issues and prospects.Crossref | GoogleScholarGoogle Scholar |

Saggar S, Singh J, Giltrap DL, Zaman D, Luo J, Rollo M, Kim D-G, Rys G, van der Weerden TJ (2013) Quantification of reductions in ammonia emissions from fertiliser urea and animal urine in grazed pastures with urease inhibitors for agriculture inventory: New Zealand as a case study. The Science of the Total Environment 465, 136–146.
Quantification of reductions in ammonia emissions from fertiliser urea and animal urine in grazed pastures with urease inhibitors for agriculture inventory: New Zealand as a case study.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3sXhsVOksLzI&md5=efa8b7fa2d9109b08cf0bf6b7fa1de1fCAS |

Sanchez PA (2002) Soil fertility and hunger in Africa. Science 295, 2019–2020.
Soil fertility and hunger in Africa.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD38Xit1Oju74%3D&md5=966141a6671c387adbd062beae985585CAS |

Sattari SZ, Bouwman AF, Martinez Rodriguez R, Beusen AHW, Ittersum MK (2016) Negative global phosphorus budgets challenge sustainable intensification of grasslands. Nature Communications 7, 10696
Negative global phosphorus budgets challenge sustainable intensification of grasslands.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC28Xisl2iurc%3D&md5=53ddbac41f0f376cfbffc01c1379f47aCAS |

Scheer C, Rowlings DW, De Antoni Migliorati M, Lester DW, Bell MJ, Grace P (2016) Effect of enhanced efficiency fertilisers on nitrous oxide emissions in a sub-tropical cereal cropping system. Australian Journal of Soil Research 54, 544–551.
Effect of enhanced efficiency fertilisers on nitrous oxide emissions in a sub-tropical cereal cropping system.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC28XhtlejtL%2FP&md5=dc9d33d3524f86c00722ea0a129793fbCAS |

International Plant Nutrition Institute (IPNI) Scientists (2014) Nutrient performance indicators: the importance of farm scale assessments, linked to soil fertility, productivity, environmental impact and the adoption of grower best management practices. Ref #14061. Available at http://www.ipni.net/issuereview [verified 14 May 2016].

Singh J, Saggar S, Bolan NS, Zaman M (2008) The role of inhibitors in controlling the bioavailability and mitigation of nitrogen losses in grassland ecosystems. Developments in Soil Science 32, 329–362.
The role of inhibitors in controlling the bioavailability and mitigation of nitrogen losses in grassland ecosystems.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1cXhtVKgtL3E&md5=ba3214610be8c56edc13e3b081d6245eCAS |

Snyder CS, Fixen PE (2012) Plant nutrient management and risks of nitrous oxide emission. Journal of Soil and Water Conservation 67, 137A–144A.
Plant nutrient management and risks of nitrous oxide emission.Crossref | GoogleScholarGoogle Scholar |

Snyder CS, Bruulsema TW, Jensen TL, Fixen PE (2009) Review of greenhouse gas emissions from crop production systems and fertilizer management effects. Agriculture, Ecosystems & Environment 133, 247–266.
Review of greenhouse gas emissions from crop production systems and fertilizer management effects.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD1MXptl2ht7w%3D&md5=3ec38cc26b052b68b79e8ba499a425e5CAS |

Snyder CS, Davidson EA, Smith P, Venterea RT (2014) Agriculture: sustainable crop and animal production to help mitigate nitrous oxide emissions. Current Opinion in Environmental Sustainability 9–10, 46–54.
Agriculture: sustainable crop and animal production to help mitigate nitrous oxide emissions.Crossref | GoogleScholarGoogle Scholar |

Suter HC, Sultana H, Turner DA, Davies R, Walker C, Chen D (2013) Influence of urea fertiliser formulation, urease inhibitor and season on ammonia loss from ryegrass. Nutrient Cycling in Agroecosystems 95, 175–185.
Influence of urea fertiliser formulation, urease inhibitor and season on ammonia loss from ryegrass.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3sXotV2qsrs%3D&md5=4b380dcd7d746dc8059e29e232241ac6CAS |

Suter H, Lam SK, Walker C, Chen D (2015) Nitrogen use efficiency for pasture production – impact of enhanced efficiency fertilisers and N rate. In ‘Proceedings of the 17th Australian Society of Agronomy Conference’, 20–24 September 2015, Hobart, Australia. (Eds TB Acuna, M Harrison, C Moeller, D Parsons). (Australian Society of Agronomy: Warragul, Victoria, Australia)

Thapa R, Chaterjee A, Wale R, McGranahan DA, Daigh A (2016) Effect of enhanced efficiency fertilizers on nitrous oxide emissions and crop yields: a meta-analysis. Soil Science Society of America Journal 80, 1121–1134.
Effect of enhanced efficiency fertilizers on nitrous oxide emissions and crop yields: a meta-analysis.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2sXitV2ks7w%3D&md5=da8792905f723dd62dfa4f920194f7dfCAS |

Tilling AK, O’Leary GJ, Ferwerda JG, Jones SD, Fitzgerald GJ, Rodriguez D, Belford R (2007) Remote sensing of nitrogen and water stress in wheat. Field Crops Research 104, 77–85.
Remote sensing of nitrogen and water stress in wheat.Crossref | GoogleScholarGoogle Scholar |

Tomich TP, Brandt S, Ferris H, Galt R, Horwath WR, Kebreab E, Leveau JHJ, Liptzin D, Lubell M, Merel P, Michelmore R, Rosenstock T, Scow K, Six J, Williams N, Yang L (2011) Agroecology: a review from a global-change perspective. Annual Review of Environment and Resources 36, 193–222.
Agroecology: a review from a global-change perspective.Crossref | GoogleScholarGoogle Scholar |

Trenkel ME (2010) ‘Slow- and controlled-release and stabilized fertilizers; an option for enhancing nutrient use efficiency in agriculture.’ 2nd edn. (International Fertilizer Industry Association: Paris, France)

Tu S (2016) A summary report: responses of different crops to controlled release urea in China. In ‘The 4th International Conference on Slow- and Controlled-Release and Stabilized Fertilizers’, 4–6 April 2016, Beijing, China.

United Nations Environment Programme (UNEP) (2013) Drawing down N2O to protect climate and the ozone layer. A UNEP synthesis report. UNEP: Nairobi, Kenya.

van der Weerden TJ, Luo J, Di HJ, Podoloyan A, Phillips RL, Saggar S, de Klein CAM, Cox N, Ettema P, Rys G (2016) Nitrous oxide emissions from urea fertiliser and effluent with and without inhibitors applied to pasture. Agriculture, Ecosystems & Environment 219, 58–70.
Nitrous oxide emissions from urea fertiliser and effluent with and without inhibitors applied to pasture.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2MXitV2ms7zP&md5=42ec0e3447d73d2d7d810e42e87d7341CAS |

Vanlauwe B, Kihara J, Chivenge P, Pypers P, Coe R, Six J (2011) Agronomic use efficiency of N fertilizer in maize-based systems in sub-Saharan Africa within the context of integrated soil fertility management. Plant and Soil 339, 5–50.

Venterea RT, Hyatt CR, Rosen CJ (2011) Fertilizer management effects on nitrate leaching and indirect nitrous oxide emissions in irrigated potato production. Journal of Environmental Quality 40, 1103–1112.
Fertilizer management effects on nitrate leaching and indirect nitrous oxide emissions in irrigated potato production.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3MXptFKitb4%3D&md5=6678944bb6f2348f0982de2ad1457753CAS |

Venterea RT, Coulter JA, Dolan MS (2016) Evaluation of intensive ‘4R’ strategies for decreasing nitrous oxide emissions and nitrogen surplus in rainfed corn. Journal of Environmental Quality 45, 1186–1195.
Evaluation of intensive ‘4R’ strategies for decreasing nitrous oxide emissions and nitrogen surplus in rainfed corn.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2sXhs1Oqurg%3D&md5=e34b0418af1e2234263e7be6699f3481CAS |

Wang W, Park G, Reeves S, Zahmel M, Heenan M, Slater B (2016a) Nitrous oxide emission and fertiliser nitrogen efficiency in a tropical sugarcane cropping system applied with different formulations of urea. Australian Journal of Soil Research 54, 572–584.
Nitrous oxide emission and fertiliser nitrogen efficiency in a tropical sugarcane cropping system applied with different formulations of urea.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC28XhtlejtL%2FE&md5=2e15fc1fcb48cd705e0869bcd92e834fCAS |

Wang WJ, Reeves SH, Salter B, Moody PW, Dalal RC (2016b) Effects of urea formulations, application rates and crop residue retention on N2O emissions from sugarcane. Agriculture, Ecosystems & Environment 216, 137–146.
Effects of urea formulations, application rates and crop residue retention on N2O emissions from sugarcane.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2MXhs1GjsrvN&md5=d0bcad5ed9c1644e7a7573757a16eaeaCAS |

Weber C, McCann L (2015) Adoption of nitrogen-efficient technologies by U.S. corn farmers. Journal of Environmental Quality 44, 391–401.
Adoption of nitrogen-efficient technologies by U.S. corn farmers.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC2MXkvFSjsrk%3D&md5=fbc14b1defbe45bc8da404f94c22d75fCAS |

Wolt JD (2004) A meta-evaluation of nitrapyrin agronomic and environmental effectiveness with emphasis on corn production in the Midwestern USA. Nutrient Cycling in Agroecosystems 69, 23–41.
A meta-evaluation of nitrapyrin agronomic and environmental effectiveness with emphasis on corn production in the Midwestern USA.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BD2cXjtlyjt78%3D&md5=37d180f32c998c07655823c10d811994CAS |

Wu A (2016) Technical summary of global enhanced efficient nitrogen fertilizers. AgroNews. Available at http://news.agropages.com/News/NewsDetail---19821.htm [verified 14 May 2017].

Xu M, Li D, Li J, Qin D, Hosen Y, Shen H, Cong R, He X (2013) Polyolefin-coated urea decreases ammonia volatilization in a double rice system of southern China. Agronomy Journal 105, 277–284.
Polyolefin-coated urea decreases ammonia volatilization in a double rice system of southern China.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC3sXnsVOltrc%3D&md5=1c919efcaa5d88a2af0052fb1547cb68CAS |

Yang Y, Zhang M, Li YC, Fan X, Geng Y (2012) Controlled release urea improved nitrogen use efficiency, activities of leaf enzymes, and rice yield. Soil Science Society of America Journal 76, 2307–2317.
Controlled release urea improved nitrogen use efficiency, activities of leaf enzymes, and rice yield.Crossref | GoogleScholarGoogle Scholar | 1:CAS:528:DC%2BC38XhvVelsbzI&md5=6d8a0deafd75d83fb2d8fea415246404CAS |

Ye Y, Lianga X, Chena Y, Liua J, Gub J, Guob R, Li L (2013) Alternate wetting and drying irrigation and controlled-release nitrogen fertilizer in late-season rice. Effects on dry matter accumulation, yield, water and nitrogen use. Field Crops Research 144, 212–224.
Alternate wetting and drying irrigation and controlled-release nitrogen fertilizer in late-season rice. Effects on dry matter accumulation, yield, water and nitrogen use.Crossref | GoogleScholarGoogle Scholar |

Zingore S, Njoroge S, Chikowo R, Kihara J, Nziguheba G, Nyamangara J (2014) 4R plant nutrient management in African agriculture: an extension handbook for fertilizer management in smallholder farming systems. International Plant Nutrition Institute: Nairobi, Kenya. Available at http://ssa.ipni.net/ipniweb/region/africa.nsf/0/79A037DA41071A8043257D9A0054739B/$FILE/4R%20Extension%20Handbook.pdf [verified 14 May 2017].