Problems and solutions Dr Mark Shepherd ADAS

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

Water quality: monitoring sites

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.

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.

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

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..)

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.

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.

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

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)

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

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

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

Example results

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

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?

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