Farmyard point sources a hidden factor in waterways pollution says new study

Overlooked channels from farmyards play a bigger role in phosphorus and nitrogen pollution of rivers and streams than watercourses from land

Deceptive: This stream looks clean buts its waters are badly contaminated by farmyard effluent.
Deceptive: This stream looks clean buts its waters are badly contaminated by farmyard effluent.
Ciaran Moran

Ciaran Moran

DIRECT sources from farmyards are a more significant source of phosphorus and nitrogen pollution of rivers and streams than water-courses from fields, according to a new study.

A research team, led by Dr Simon Harrison of University College Cork, studied the environmental impact of specific discharges from farmyards.

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The study involved the analysis of water chemistry throughout multiple streams and man-made drains within a single drainage network in a predominantly dairy farming catchment area in the south of Ireland.

The team concluded that many of the issues observed are contrary to current regulations on good agricultural practice .

Enforcement is also an issue, says Dr Harrison.

"The problem here is policing these issues. We don't want to go around penalising farmers and taking out a big stick to them," he said.

"Farms are messy places, we all know that. What we need is some kind of measure that would soak this stuff up, and that would deal with it."

Dr Harrison said that modern intensive dairy farming is much more likely to produce excessive discharges from farmyards.

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"It's a function really of the number of cows that are out there. If you have more cows, you have more manure and you have more silage. Therefore, you have more stuff available to run off," he explained.

"Almost all farmyards have been there for many generations, with cattle coming in and out of the yard on a daily basis.

"So there is a whole lot of manure all over the place and, in Ireland, it obviously rains a lot.

"When the rain hits the yard, the concrete or the hard standing, it's going to wash off a whole load of polluted water somewhere.

"Over many generations, farmers have channelled it into a stream to get rid of it.

"The trouble is that those point sources from farmyards are polluting the streams quite badly," he maintained.

Dr Harrison stressed that it is these specific small point or particular sources that are causing the problem rather than diffuse sources from fields.

"These point sources need to be tackled," he said.


To carry out the research the survey team literally put boots on the ground.

"Most studies on effects of agriculture on catchment water quality collect data over a long period of time from a few sampling points," said Dr Harrison.

"But these studies can only weakly infer where the pollution is actually coming from.

"To tackle this, we instead collected data from lots of different locations dotted throughout the catchment and found that there were lots of small, discreet - but highly polluted - sources entering the stream network."


The research team found that in the headwaters where yards are discharging directly into the drains and streams, the water quality was very poor.

"Little streams and drains full of phosphorus and particularly ammonium," said Dr Harrison.

"The cows themselves are drinking from these streams, so upstream manure sources are also contaminating them.

"Many of these streams are nursery areas for fish such as trout. Allowing manure and other organic matter into these streams is not without consequence."

The more significant issue, Dr Harrison warned, is drinking water quality and the impact particularly of the input of faecal bacteria into the water on humans .

He also highlighted that leakage from silage and silage pits as a big factor in watercourse pollution at particular points during the year - for example when fresh silage clamps are established in yards, or when they are opened in late autumn.


Dr Harrison said there are measures that could be implemented such as developing wetlands. However, he noted that these are expensive to build, they take a lot of land, and their impact is still uncertain.

"The farmyard drains themselves. . . if they are engineered differently, it might help to mitigate the problem.

"However, the issue for many farmers is that slurry storage doesn't have sufficient capacity for farmyard run-off."

Covering the yard, he said, is the ideal solution. However, he conceded that this would cost a lot of money and wasn't a realistic solution.

"We can explore wetlands, better nutrient management, better water management, all of which cost money," said Dr Harrison.

"Perhaps more important, though, is the notion that farmers are rather lax about allowing pollutants into drains and streams.

"Perhaps a more effective approach is just greater awareness amongst farmers of the need to avoid contamination of streams."

Dr Harrison stressed that farmers need to get away from the idea that a stream is convenient way to get rid of wastewater.

"That may have been the case 50-100 years ago when you had a few cows but these days with the sheer numbers of cattle and the sheer volume of silage and manure and the obvious dangers to the environment and humans downstream means that kind of lackadaisical 'ah sure look' attitude is no longer on," he said.

"It's a question of awareness raising and attitude shifting as much as specific measures."

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