Component report for Defra Project NT2605 (CSA 6579)
WP 7. Scenario testing
Peter Dampney and David Harris, ADAS Boxworth
Brian Chambers, Fiona Nicholson and Gillian Goodlass, ADAS Gleadthorpe
and
Steven Anthony, ADAS Wolverhampton
March 2006
Contents
1. Executive Summary 4
2. Introduction 6
2.1 The NT26 Research programme 6
2.2 The NT2605 project 7
2.3 WP7. Scenario testing 7
3. Scope and methodology 8
3.1 Scope of the scenario testing 8
3.2 Scenario definitions 8
3.3 Scenario testing process 9
3.4 Fertiliser-N use 13
4. Ammonia emissions 14
4.1 Modelling ammonia emissions from fertilisers 14
4.2 Scenario outputs 14
5. Profitability of UK agriculture 17
5.1 Sources of information and methodology 17
5.2 Scenario outputs 22
6. Quantity of fertiliser products 24
7. References 25
Appendix 1. Fertiliser-N use for each scenario
Abbreviations
AnA / Anhydrous ammonia
AN / Ammonium nitrate
AS / Ammonium sulphate
nBTPT / N-(n-butyl)-thiophosphoric triamide urease inhibitor
CAN / Calcium ammonium nitrate
CEC / Cation exchange capacity
DCD / Dicyandiamide nitrification inhibitor
DNDC / DeNitrification - DeComposition
EF / Emission factor
EU / Edinburgh University
FFD / Freshwater Fish Directive
GC / Gas chromatography
HRI / Warwick HRI
IGER / Institute of Grassland and Environmental Research
IPCC / Intergovernmental Panel on Climate Change
N / Nitrogen
NH3 / Ammonia
NH4 / Ammonium
N2O / Nitrous oxide
NO2 / Nitrite
NO3 / Nitrate
NVZ / Nitrate Vulnerable Zone
QuB / Queens University, Belfast
RR / Rothamsted Research
U / Urea
U+Ag500c / Urea granules with 500ppm of nBTPT urease inhibitor (coated onto granule)
U+Ag500m / Urea granules with 500ppm of nBTPT urease inhibitor (in the melt)
UAN / Urea ammonium nitrate solution
UAN+Ag500 / Urea ammonium nitrate solution with nBTPT urease inhibitor (500ppm of urea-N)
UAS / Urea ammonium sulphate
UKAEI / UK Ammonia Emissions Inventory
WFPS / (Soil) water-filled pore space
ppmv / gas concentration in parts per million by volume (equivalent to mmol mol-1)
1. Executive Summary
1. Alternative reactions of farmers to defined scenarios were determined by a group of experienced advisers and researchers, taking account of a wide range of factors and information. The impact of these changes on ammonia emissions and farm profitability compared to the current (Baseline) situation, were assessed.
Ammonia emissions
2. Ammonia emissions were modelled using the NT26-AE model that has been developed as part of the NT26 research programme. The Baseline ammonia emissions resulting from current fertiliser-N use (57kt NH3 /year) were higher than previous estimates (35kt NH3 /year), mainly due to the recent NT2605 research information showing that the ammonia emission factor (EF) for arable cropping (22%) was higher than the EF of 11.5% in the UK Ammonia Emissions Inventory.
3. If all current use of straight AN was switched to straight urea without use of the Agrotain (nBTPT) urease inhibitor, the modelled emissions from fertiliser use would increase from 57kt NH3 /year (Baseline) to 154kt NH3 /year. The total projected UK emissions (2010) would increase from 285kt NH3 /year (Baseline) to 382kt NH3 /year which is well above the current 297kt NH3/year UK emissions target.
4. If all current use of AN-based fertilisers (straights and compounds) was switched to urea-based fertilisers without use of Agrotain, the modelled ammonia emissions from fertiliser use would increase from 57kt NH3 /year (Baseline) to 242kt NH3 /year.
5. If the rate of N application as urea-based fertiliser also increased by 20% compared with the use of AN-based fertilisers (as indicated by the NT26 ammonia emission and crop response studies), then the modelled ammonia emissions from fertiliser would increase to 288kt NH3 /year. Under this worst case scenario, the total projected UK emissions would be 516kt NH3/year which is nearly double the current 297kt NH3/year UK emissions target.
6. Use of the Agrotain urease inhibitor would have a substantial mitigating effect on ammonia emissions from urea-based fertilisers. If all current use of AN-based fertilisers was switched to urea-based fertilisers, then the use of Agrotain with all urea-based fertilisers would reduce total ammonia emissions to roughly 65% of that if Agrotain was not available.
Farm profitability
7. The current overall profitability of UK farming is estimated as £159 million including subsidies. The range of estimated changes in this overall profitability for each scenario were:
S3A: - £26m to + £31m
S3B: - £25m to + £32m
S5A: - £128m to - £45m
8. In scenarios S3A and S3B (where AN-based compound fertilisers continue to be available), the main impacts on profitability were estimated to come from small crop yield losses and changes in the price of fertiliser-N.
9. The assumed differences in the purchase price of nitrogen fertiliser were based on current fertiliser prices and differentials. Since these prices are currently increasing and very volatile due to the increasing price of energy, any estimates of future actual N prices or differentials between different fertiliser-N materials must be treated with great caution.
10. A switch from AN to CAN was estimated to reduce farm profitability by £24m mainly due to the extra cost of N as CAN. A switch from AN to urea would increase profitability by £31m assuming that urea-N is cheaper than AN-N, but also assuming that there would no loss of crop yield or quality. If application rates of urea-N were increased by 20% to maintain crop yields and quality (as shown by the NT2605 research), then the estimate would be for a £28m reduction in profitability.
11. If urea was treated with Agrotain, it was estimated that there would a £19m increase in profitability. This is a smaller increase than from the switch of AN to urea (untreated) but is less likely to result in losses of crop yield or quality.
12. Large financial reductions were estimated if all AN-based straight and compound fertiliser materials would not be available, due to the assumption that urea-based NPKS compound fertilisers would not be available. This would result in more application passes being needed in order to apply the full range of major nutrients needed for crop production.
13. It was estimated that a switch from AN to CAN would increase the current total quantity of fertiliser-N products used and transported to farms by about 10% (4,020 to 4,400kt/year). A switch from AN to urea would reduce this quantity by about 10%, assuming there is no change in total N use. However, as a typical lorry payload for urea is 24t (15% less than the typical payload of 28t for AN), this reduction would mean only a small reduction in the total number of lorry movements required.
2. Introduction
2.1 The NT26 Research programme
The NT26 research programme was set up by Defra to investigate the nitrogen (N) loss pathways, the environmental and economic impacts, and the response of agricultural and horticultural crops to different forms of fertiliser-N. The NT2605 project was part of a suite of projects in this programme as shown below (Final report submission dates shown in brackets).
NT2601 / Desk study reports on:· Nitrogen fertilising materials (June 2003)
· Production and use of nitrogen fertilisers (August 2003)
NT2602 / Desk study report on:
· Evaluation of urea-based nitrogen fertilisers (October 2003)
NT2603 / Report of field studies (2002/03 cropping season):
· The behaviour of some different fertiliser-N materials (March 2004)
NT2604 and
NT2606 / Facilities construction:
· Ammonia emissions from nitrogen fertilisers – wind tunnel construction (March 2004)
NT2605 / This project
NT2610 / Report of field studies (led by Silsoe Research Institute):
· Spreading accuracy of solid urea fertilisers (August 2005)
The following leading UK agri-environment research organisations participated in all NT26 projects (except NT2610), including the NT2605 project reported here.
· ADAS UK Ltd
· Edinburgh University (EU)
· Warwick HRI (HRI)
· Institute of Grassland and Environmental Research (IGER), North Wyke
· Queens University, Belfast (QuB)
· Rothamsted Research (RR)
· SAC Commercial Ltd (SAC)
The project was led by Peter Dampney, Principal Research Scientist, ADAS Boxworth Research Centre, Cambridge who was the main point of contact with the Defra NT26 Steering Group.
2.2 The NT2605 project
The NT2601, NT2602 and NT2603 projects provided the basis for the field experimental and other work carried out in NT2605 in cropping seasons 2003/04 and 2004/05. The overall aim of the project was to develop working decision support systems (DSS) to evaluate the agronomic, environmental and economic impacts that would result from changes in the use of different fertiliser-N materials in UK agriculture. More specifically, project work packages (WP) covered the following topic areas:-
WP1a / To investigate crop responses to different fertiliser N forms.WP1b / To generate robust ammonia emission algorithms and emission factors for predicting the loss of ammonia following application of different fertiliser N forms under a range of crop, soil and environmental conditions. To evaluate the relationship between ammonia loss and crop N use efficiency as a potential basis for revising current national standard nitrogen fertiliser recommendations (Defra, 2000).
WP2 / To generate robust nitrous oxide emission factors for predicting losses following application of different fertiliser N forms under contrasting crop, soil and environmental conditions.
WP3 / To determine the optimum formulation method, addition rate and method of use of urea treated with the urease inhibitor nBTPT (Agrotain), to maximise its ammonia abatement potential and efficiency of N use by crops, whilst minimising any adverse phytotoxic effects.
WP4 / To assess the risk of ammonium-N, nitrite-N or urea-N losses to surface waters and groundwaters following the application of urea-based N fertilisers.
WP5 / To assess the potential for urea or urea+Agrotain to cause phytotoxic effects during establishment, in growing crops, or in marketable produce.
WP6 / To construct a decision support system that will assess the economic impacts of changes in the availability of different forms of N fertiliser on different farm types and UK agriculture.
WP7 / To estimate and evaluate the agronomic, environmental and economic impacts at both farm and national levels that would result following different hypothetical scenarios concerning the availability of N-containing fertilisers to UK farmers.
Reporting of the NT2605 has been structured into a suite of 8 component reports, one for each work package plus an over-arching Executive Summary for the whole project. Each report is self contained with its own Executive Summary, but interacts with data and conclusions from other WPs where appropriate.
2.3 WP7. Scenario testing
The aim of this work package was to provide relevant outputs on the impact of defined scenarios on nitrogen losses to the wider environment, and the economics of farm businesses and UK agriculture. This report describes the methodology and information sources used in the scenario testing, and the outputs.
3. Scope and methodology
3.1 Scope of the scenario testing
At an early stage, the NT26 Steering Group agreed that the NT2605 project should assess the impact of defined scenarios on the economics of farm businesses and UK agriculture, and on nitrogen losses to the wider environment. Other impacts (e.g. on the fertiliser industry) were agreed to be outside of the scope of this project.
Ammonia emissions to the atmosphere was the main environmental issue considered in a quantitative way, and full details of the scenario testing on ammonia emissions are given in section 4. Assessments on farm profitability are given in section 5.
Other nitrogen loss pathways (ammonium-N losses to waters, nitrous oxide emissions to the atmosphere) were not considered in detail, as research within the NT26 research programme has shown that the impacts of changes from AN to urea-based fertiliser-N materials on these loss pathways will be small (Macdonald et al. (2006); Smith et al., 2006).
3.2 Scenario definitions
The definition of each scenario to be evaluated was provided by Defra (Table 1) and resulted from inter-departmental discussions. The impacts of scenarios S1A, S3A, S3B and S5A were evaluated in this work package.
Table 1. Scenario definitions
S1A / Baseline situation. No further restrictions on AN use.S2A / Increased restrictions on storage, transport and sale of AN.
S3A / Removal from market of AN and NPK fertilisers containing more than 28% N from AN. CAN is available. Assume current price differentials continue. Agrotain urease inhibitor adds 5% to urea cost.
S3B / Removal from market of AN and NPK fertilisers containing more than 28% N from AN. CAN is not available. Assume current price differentials continue. Agrotain urease inhibitor adds 5% to urea cost.
S4A / Removal from market of AN and NPK fertilisers containing more than 21% N from AN. CAN is available. Assume current price differentials continue. Agrotain urease inhibitor adds 5% to urea cost.
S5A / Removal from market of all AN-based fertilisers. Assume current price differentials continue. Assume unrestricted imports. Agrotain urease inhibitor adds 5% to urea cost.
3.3 Scenario testing process
A group of experienced advisers and researchers agreed the most likely reaction of farmers to each of the scenarios defined in Table 1, taking account of a wide range of factors reflecting current practice, and the requirements and perceptions of different farm types. Members of this group were:
Peter Dampney (ADAS, NT2605 Project Leader, leader of WP7)
Andrew Wells (The Arable Group, TAG)
Nick Holt-Martyn (The Dairy Group)
Bill Basford (ADAS Associate)
Gillian Goodlass (ADAS Soil Scientist)
Likely changes in fertiliser practice on 8 main crop types were considered – winter cereals, spring cereals, oilseed rape, potatoes, sugar beet, brassicae, grass (grazed), grass (cut and grazed). Wherever possible, objective information was used. However, since farmers inevitably react in different ways to change, even farmers with the same farm system and in the same general location, significant expert judgement was also used.
The following assumptions were made when considering each scenario:
- The ‘%N from AN’ in the scenarios (sometime called the ‘AN equivalence’) is calculated as twice the lower of the ammonium-N (NH4-N) or nitrate-N (NO3-N) content of the fertiliser material. It is often, but not always, similar to the total N%. For instance, the product 27:0:0+30S has a total N content of 27%, but the ‘N from AN’ is only 16.4%. Table 2 shows all currently available commercial NPK compounds produced by Kemira and Yara, with their contents of NH4-N, NO3-N, total N and N from AN.
- There would be no supply problems for the currently available fertiliser-N materials.
- The total use of fertiliser-N would remain unchanged from the Baseline, except for the ‘Max’ assumption (see below) where urea-N application rates were increased by 20% to reflect the higher economic optimum N rates for this fertiliser-N material compared to AN.
- Farming systems would not change compared to the Baseline due to factors other than the availability of fertiliser-N materials – i.e. any impact of the new CAP regime has not been taken into account as these were considered to be too unpredictable. For instance, restructuring of both livestock and tillage crop enterprises may occur over the next few years due to economic and regulatory (e.g. Nitrate Vulnerable Zone (NVZ) Action Programme rules) pressures.
- Urea-based NPK blended fertilisers would not be widely available. Although some urea-based blends are currently commercially available in the UK, there are significant potential practical problems in their use due to the hygroscopic (water absorbing) nature of urea. Informed opinion was that such blends would have limited potential for mass production, though little scientific or objective information could be found.
- There would be no adverse effect on crop quality of high quantities of sulphur (S) use. Excess sulphur can induce copper deficiency in dairy cows or other cattle but very high levels are needed.
A crucial part of the scenario testing process was identification of the Baseline situation (scenario S1A). This was based on the most recent data available, and represented the most accurate assessment of the current impact of agriculture on the environment and farm economic situation. The impact of each scenario was related to this Baseline.