How does fertiliser use impact on water quality?
The water quality of lakes and within water bodies can be affected by increased nutrient inputs, particularly nitrogen and phosphorus. If other conditions, such as temperature and light are conducive to growth, high nutrient levels in water can lead to eutrophication (excessive weed and algal growth). In addition, accumulation of nitrate in water sources can result in the World Heath Organisation’s recommended limits being exceeded.
Sources of nutrient could be excessive fertiliser use resulting in run-off or leaching, or effluent or urine from stock with nutrients leaching into groundwater and then waterways, or livestock effluent directly entering streams and rivers.
Non-agricultural inputs include sewage treatment discharges and urban stormwater run-off.
Fertiliser nutrients might enter waterways if best management practices for fertiliser use are not followed. This includes spreading fertiliser too close to waterways, fertilising shortly before heavy rainfall, fertilising in windy conditions and using excess fertiliser.