1. Problems and solutions
Dr Mark Shepherd
ADAS

2. Background Quality of life? UK plc?
Rising nitrate concentrations in water
Ground waters at risk
Surface waters at risk

3. Water quality: monitoring sites

4. Soil mineral N measurements
Sort this – by crop (cereals, other, grass); and check permeable v clay sites. Check it’s up to date
High values after potatoes, peas, intensive grassland
Low after sugar beet – but often higher the next winter.

5. Nitrate concentrations
Groundwater catchments
Comment: Patterns similar to SMN, (fewer sites though)
All averages are > 50 mg/l. This reflects partly the dry winters, but even in average winters most arable values on these soils would exceed 50.
Even grassland is > 50 – including the few clover-grass fields monitored.

6. Nitrate loss after crops
After Potatoes
After potatoes, concs can be very high. Pattern of elution is same as for cereals.
Beet is late harvested, so pattern is reversed – low start, increasing especially after harvest.
Blue bars are 50 mg/l nitrate.
After Sugar Beet

7. Clay soils: (Surface water catchments)
May require different mitigation:
Cracks/drains provide rapid transfer to streams
Greater risk of transfer of all pollutants from surface applications (P, NH4, FIOs..)

8. Nitrate concentrations
Surface water catchment: Devon
Pugsley =Intensive dairy farm. High SMN in autumn. Monitoring is of the stream which drains the farm as there are few farm drains.
Concs exceed 50 for much of the winter. Large rainfall causes dilution especially in later winter.
Edgworthy is more extensive; and here the concentrations tend to be lower, but increase during high flows, presumably due to manure/excreta on the surface. The increased concs at Edgworthy are due to manure and fertiliser applications in spring.
These elevated concs may therefore carry P with them, at a time of year when the impact on eutrophication could be important.

9. Nitrate concentrations
Surface water catchment: Norfolk
Extensive grass farm. Concs generally well below 50 mg/l nitrate (11 mg/l N) but heavy rain tends to cause an increase in concentration. This is attributed to the high N concs at the surface (due to grazing returns) – in heavy rain, N is dissolved here then finds a rapid route to the drain/ditch.
Here, the ‘drain’ site receives limited fertiliser. But there is a spike in February when fertiliser N was applied. This is smoothed out in the ditch data which contains the whole group of several fields.
Conversely, one of the other fields was ploughed out and reseeded in autumn, with large applications of manure just before ploughing. This is the main cause of the large spike in concs in autumn, which gradually diminishes as the crop establishes.
Comment also on the value of field/farm scale, because the individual events get harder to see, the larger the contributory area.

10. Best management practices - we know a lot!
NH3
N2O
Management approaches:
Fertiliser
Soil
Crop
Animal
Manure
Farm structure

11. Developing the knowledge
Systems experiments: arable
Delay cultivation
Average NO3 concentration (mg/l)
Cover crop
154
226
148 51
258
106
139
186 44
179 45
132
105 69
128
Min. till
Half N rate
64 mg/l
167
131 96
Shallow soil (30 cm) over limestone
5 year rotation
Johnson et al. (2002)

12. Developing the knowledge
Systems experiments: animal production
De Marke Exp. Farm
Rotz et al. (2005)
Outputs
Inputs
Surplus
Management:
Animal - diet, stocking rate
Fertiliser - rate, timing
Efficiency
16%
35%
Rotation - clover, maize
Grazing - day, season
Manure - method, time
Cultivation & cover crops

13. Applying the knowledge
Measure Type:
- Source Control
Measure Cost:
- Specific to Farm
Measure Effect

14. Cost-curve calculation
Cost-effectiveness assessment
Establish Buffer Strips
Manure Incorporation

15. Example results

16. Cost vs on-farm benefit
Storage costs amortised over 20 years and spreader costs 10 years.
Fertiliser N value = 40p/kg
10000
9000
8000
Ammonia-N saved
Spreader
7000
Nitrate-N saved
6000
£/year
5000
4000
Storage
3000
2000
1000
Cost
N Yorks
Shrops
Devon

17. Conclusions
We have much of the basic scientific understanding - but we need to be able to apply to the catchment-scale
This is only half of the battle:
Resources for farm/field level investigation?
Bringing about change?
Assessing costs and benefits?

18. Co-financing for this work by The European Commission is gratefully acknowledged.