Nitrogen Cycling: Risks and Opportunities - Keith Goulding (Rothamsted Research)


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Nitrogen cycling on farms

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Nitrogen Cycling: Risks and Opportunities - Keith Goulding (Rothamsted Research)

  1. 1. Nitrogen cycling: risks and opportunities Keith Goulding Head: Department for Sustainable Soils and Grassland Systems Rothamsted Research
  2. 2. Driving forces for better N utilisation  Projected population increase requires 50% more food by 2030; 70% more by 2050.  Royal Society says we need ‘Sustainable Intensification’. Cultivating more land risks destruction of forests and large carbon losses.  N is the key to yield in most countries, but making N fertiliser uses fossil fuels and produces greenhouse gases.  Must improve NUE to reduce costs, fossil fuel use and losses to air and water. NB some room for greater use of legumes but not wholesale switch.
  3. 3. Example: problem of poor NUE of meat production. Intensive pig production from field to fork ‘Reactive nitrogen in the environment.’ UNEP 2007
  4. 4. Example: N surpluses on some UK farms N surplus (= N inputs – N in product; kg N/ha) Fertiliser N input (kg N/ha) sheep arable dairy pig/arable organic dairy (clover)
  5. 5. At the core, the complicated nitrogen cycle
  6. 6. Organic Matter Microbial Biomass NH4 + NO3 - Immobilisation NitrificationAmmonification Death & decomposition Mineral N Organic Matter Mineral N Approximate N content (kg ha-1 ) : 2000-20000 10-500 Mineralisation Importance of N in soil organic matter But still no quick and easy way of predicting N release from soils
  7. 7. Worst case scenario for SMN? kg ha-1
  8. 8. 0 100 200 300 400 500 600 21/10/03 10/11/03 30/11/03 20/12/03 09/01/04 29/01/04 18/02/04 09/03/04 29/03/04 18/04/04 SoilWaterNitrate(ppm) 0 5 Temperature(°C) Low N Plot High N Plot N release very variable through the season: nitrate in soil on Broadbalk field, Rothamsted Tony Miller, Rothamsted
  9. 9. Improving NUE  No quick fixes
  10. 10. RB209: The Basis of Good Practice  Reliable information: soil type; regular soil analysis; cropping fertiliser and manure history; nutrient balances; winter rainfall.  Realistic estimate of crop yields and fertiliser needs; take account of fertiliser prices.  Estimate SNS: RB209; PLANET, ‘Tried and Tested’  Utilise available nutrients in organic manures.  Careful selection of fertilisers – price and quality.  Correct rate, method and timing of fertiliser and manure applications; accuracy.  Good record keeping.
  11. 11. Probably not like this! Better manure management
  12. 12. Better manure management  Estimate or measure N content (RB209; MANNER); make allowance when calculating fertiliser applications  Recycle effectively – band spreading; injection  Where possible, apply from late winter onwards  Measure application rate  Manure Management Plan
  13. 13. ‘Tried & Tested’ SNS calculator You can use our SNS calculator to help you determine the Soil Nitrogen Supply of your soil. You will need this index number when using the ‘Fertiliser Manual (RB209)’ for guidance on fertiliser application rates. Tried & Tested SNS Calculator
  14. 14. Improving NUE involves assessing risk and eliminating ‘leaky’ practices N leached (kg ha-1 )
  15. 15. Could also consider:  Min Till  Precision seeding and fertiliser application  Fertigation
  16. 16. Acknowledgements Rothamsted Research is an institute of the UK Biotechnology and Biological Sciences Research Council. The UK Department for Environment, Food and Rural Affairs funded some of the research described in this talk.