Two of the most potentially toxic pollution sources on farms this summer

Farmers are being advised to be conscious that some of the worst waterways pollution happens over the summer months.

Alan Morrow, Countryside Management Delivery Branch, from the Northern Ireland Department of Agriculture, Environment and Rural Affairs, says that over the years some of the most serious agricultural pollution incidents have occurred during the summer months, with many occurring when field and weather conditions were perfect for slurry spreading.

“While the nitrogen (N) value obtained from slurry is at its greatest when applied in spring, slurry applied to land after silage has been cut can also make a valuable contribution to the nutrient requirement of the next cut.”

Summer time, he said, is often when most serious agricultural pollution incidents have occurred during the summer months, with many occurring when field and weather conditions were perfect for slurry spreading.

“There are a number of reasons why this is the case. Dissolved oxygen is essential for a wide range of aquatic life including fish and one of the most common causes of a fish kill is a reduced oxygen supply in the water. The amount of oxygen dissolved in water decreases at higher summer temperatures.

“Reduced oxygen carrying capacity often coincides with low summer flows which effectively reduces the potential of a waterway to dilute any pollutants. In these conditions pollution control on the land and farmyards even remotely connected to a waterway must be of the very highest standard to minimise the risk of a pollution incident.”

Pollution potential

The breakdown of most farm pollutants requires oxygen and the Biochemical Oxygen Demand (BOD) is a measure of the amount of oxygen needed by micro-organisms to break down organic material. A material with a high BOD value means high pollution potential if it makes its way to a waterway.

pollutants
Source: DAERA

Carry out those seasonal checks

The table above illustrates that silage effluent is one of the most potent sources of pollution on the farm.

According to Alan, it is important to ensure that none of it escapes to a waterway, no matter how minor.

“Remember that it can continue to flow for a long time after grass has been ensiled and for this reason you should regularly check the level of effluent in your tanks. Also ensure that effluent channels can flow freely and are clear of obstruction.”

Look for signs of effluent escape as often grass will appear scorched if effluent leakage is occurring.

He also advises not to forget the drains and other farm waterways.

“No matter how thoroughly silos, channels and tanks have been examined it is essential to check beyond the farmyard. Check all waterways on the farm on a regular basis for signs of contamination.”

Indications, he said, of pollution include an unpleasant odour, discolouration or the presence of froth, foam or fungus.

“Pay particular attention to the appearance of the waterway above and below all discharge points as any change may indicate pollution.”