Your farm doesn’t need a river or stream running through it, or even a drain, for nitrate to be leaching from the farm into local rivers or streams.
This is according to Fiona Doolan from Teagasc, who was speaking on the clover walk on the farm of Thomas and David Fennelly near Emo in Co. Laois this week.
Nitrate
Speaking on nitrate loss to water courses at the event, Doolan said: “To lose nitrate from your farm you don’t need the river, you don’t need the stream and you don’t even need the drain on the farm.
“That’s a big thing to say,” she said.
Doolan explained that nitrate is being lost through the soil and it is going down through the soil and into the groundwater below.
Explaining to the large crowd in attendance, she said: “Once nitrate gets down that far it is gone, it is gone past the roots, we will never get it back again.
“Nitrate as a nutrient is very mobile. Once it starts moving it keeps moving, it doesn’t bind tightly to the soil itself.
“So that nitrate will then surface wherever the closest river or stream is. That will stay moving through the river and end up where that river meets the sea.”
Speaking to the crowd, Doolan said: “You could say ‘what effect will that have on me, it is not affecting my local river or stream’.
“Firstly, that is money that has flown down the river and second, it has a detrimental effect when it meets the sea.
“We have a 16% decline in water quality in our harbours and estuaries, and the problem we have with that is that 85% of that nitrogen has come from agriculture – we are the main source of it.
“It is a land-based issue, [but] when it comes to nitrogen it is an agricultural industry issue.
“We really have to take ownership to prevent this from happening,” she said.
Controlling loss
Doolan explained to the farmers present that for that nitrate to be lost, three things are required.
The first of these is predominately free-draining soil. The second is nitrate that is in the soil that isn’t being taken up by the crop; if we have nitrate in the soil where there isn’t sufficient demand from the crop that is surplus and is really at risk of being lost.
“Really what I am asking you to think about is times of the year, when there isn’t sufficient growth to take up the nitrate that is there – which is the start and end of the year when growth rates are tailing off or haven’t taken off yet,” Doolan said.
“They are the really risky periods, because generally when you hit late-spring or summer you are looking at good growth rates.
“When we talk to farmers, when we talk about nitrate loss we begin to think that it is just related to chemical nitrogen, and it is not.
“The pool of nitrate in the soil is all the same regardless of where it came from, so when we talk about getting the most out of the nitrate in your slurry or farmyard manure it is the same as the chemical fertiliser.”
The third thing needed, Doolan said, is a vehicle to move it down through the soil – and this is rainfall.
“When these three things happen, that is when we are really at risk of losing nitrates,” she said.
To reduce nitrate loss from farms Doolan recommended that farmers look at reducing their reliance on chemical nitrogen and get the most out of organic fertilisers.
Farmers should also be looking to improve nutrient use efficiency by timing and management of chemical and organic fertiliser applications.
She also suggested that farmers be aware of the risky time and places when spreading chemical and organic fertilisers.