Pollution of Water by Agriculture

Vicki Chapman Vanina Guevel Anne Newson Tony

Situation Before : organic waste as fertilizers environment not a priority Now : intensive agriculture improved techniques mineral fertilizers pesticides tests available

How serious is the problem?

What factors pollute water? Nutrients Slurry Pesticides Chemicals Milk effluents Silage effluents Animal carcasses Heavy metals Erosion Seeds

Causes of all farm pollution incidents

Nutrients Main nutrients - nitrogen, phosphorus, potassium Source - fertiliser, manure, rainfall, sewage, silage, etc. EC Limit - rivers must not exceed the 50 mg N /litre of water

Stimulate crop growth. A limit of 250 kg total N/year/ha is recommended from livestock manures The loss of the nutrients through soil percolation and land runoff, into the waterways causes disruption to the balance of the aquatic habitat.

Slurry Source – a mixture of animal dung and urine, Est. 200 million tonnes undiluted excreta produced annually in UK, 50% slurries. Most slurry stored in earth bank lagoons estimated total volume is 15.5 million m 3

Virtually all livestock waste is recycled to the land causing 17% of water pollution from agriculture to come from slurry. There is a restriction of 10m 'no spreading' zone adjacent to all water courses, direct spillage is highly prosecuted. Improvements in available grants have improved slurry stores, decreasing incidence from 99 incidents in 1991 to 28 in 1996.

Pesticides Herbicides Fungicides Insecticides Molluscicides Rodenticides Growth regulators Sheep dips … about 450 different products

Get into river by run-off into drains, leaching from soil, spray drift into watercourse, washings High persistence and toxicity Kill fish, amphibians, invertebrates and plants Accumulation in lipids and sediments Trace concentrations hard to measure Long-term effects often unknown

Milk and chemicals Milking parlour washing effluents Waste milk spread on the fields Udder wash 400x more polluting than untreated domestic sewage

Silage effluent Very harmful and concentrated pollutant BOD level = 30,000 – 80,000mg/l. Compare to 20-60mg/l for treated sewage. Very corrosive. Hard to break down. Kills fish.

Erosion = the wearing away of the soil by wind/water Soil clogs waterways Excludes light from water Aquatic plants die No oxygen for fish and other aquatic life

Summary SUMMARY

Conclusion: How to reduce pollution Agricultural animals should have no direct contact with running water courses. Silage and slurry containers should be 100% leak-proof. Organic wastes, fertilisers, etc. should not be applied closer than 10m from the river (buffer strip) or 50m from wells or bore holes.

No intensive agriculture in “High risk areas” e.g. frozen ground, floodplain, etc. Better use of pesticides Plant new crops in stubble to reduce ploughing (see right)

Laws controlling pollution Water Act 1989 – Farmers can be fined up to £20,000 for causing pollution! Environmental Protection Act 1990 – an integrated pollution control system for safe disposal of wastes. Classification of pesticides – –Class I : forbidden (HCH, DDT, etc.) –Class II : to be reduced (PCSDs, etc.)

Hope for the future