Water monitoring scheme at Salle Farms informs strategies for reducing pollution
- Credit: Archant Norfolk
It is a perennial conundrum for farmers – how to make effective use of agro-chemicals to grow our food, while stopping pollutants from reaching our rivers, eco-systems and drinking water.
But at one Norfolk estate, an extraordinary effort is under way to analyse the effect of weather events and agricultural operations on water quality, and to find ways to mitigate any damaging impacts.
Salle Farms, near Reepham is collaborating with researchers from the UEA's School of Environmental Sciences on the Wensum Demonstration Test Catchment (DTC) project to analyse the size and causes of nutrient run-off into the water course.
Since its launch in 2011, the project has gathered a million pieces of information a year to monitor sediment composition, including pollutants like phosphates, nitrates and pesticides.
That information has been compared with meteorological data and detailed farm records on chemical applications to work out the relationships between those variables.
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One of the key findings is the impact of extreme weather events, with storms accounting for huge surges in pollutants – meaning the timing of fertiliser applications can have a major impact on whether they are retained where they are needed.
But the main focus of the mitigation effort is to keep nutrients in the soil through the use of cover crops, minimum-till cultivation and organic manure, so they are available to be used by the commercial crops and don't run wastefully into water courses.
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Farm manager Poul Hovesen, holder of the national Farmer of the Year title, has employed a seven-year rotation at the 2,000ha estate, using meticulous analysis of inputs and outputs to achieve his yield successes.
He said: 'Now, for the first time we can measure the things we achieve in the water.
'It all links together, and the biology in the soil is underestimated. We have got an interest to get the soil in a condition where it can hold the moisture in it. If you get the right structure, and the right organic matter, you can cope with the extreme weather, and the crops can take up the nutrients.
'Most importantly we do believe we have become better farmers in the process.
'If you do something that creates run-off you've done something that is damaging to the soil structure. That is one of the biggest lessons we have learned. We believe now that we can only do damage by cultivation, but I do not think that any cultivation should be a swear word.
'It should be done in the right way, because sometimes you need to loosen the soil. I don't talk about it as no-till or minimum-till – I prefer to say optimum till.'
The Defra-funded project's £100,000 main monitoring kiosk has sampled the water for phosphorus and nitrogen levels every 30 minutes since 2011 – creating a huge database spanning a varied period of weather including 2012's drought and 2013's wet winter.
Prof Kevin Hiscock of the UEA said: 'We have got a lot of high quality data and we have learned a lot about how the catchment responds to weather and storm events.
'About a third of the run-off is associated with storms, and perhaps just a few storms. So we know the catchment is sensitive to these bigger weather events. The challenge is to minimise the flux of these materials in these high-risk periods. We have this very accurate data and we can compare that with the equally detailed farm records of the application of fertilisers so we can start to create a balance of the inputs and outputs.
'What we have come to learn is if there is a period of bad weather, particularly after fertiliser application, it adds to the risk. So the farm should look to the long term forecasts before planning fertiliser applications, because there is a chance you could lose that valuable application if there is a large storm event.'
'The Wensum catchment was chosen because, under the EU Water Framework Directive, it is considered to be in a poor condition through sediment and run-off into streams and water courses. Here in the headwaters, if we can improve the water quality here it will improve the main channel and protect the Wensum.'
The project was explained to visitors this week on a tour co-hosted by Agri-Tech East, Anglian Water and the Agritech Water Cluster at the UEA.
Keeping nutrients where they are needed
During the last two years, Salle Farms has experimented with mitigation measures to reduce sediment loss and prevent chemicals like nitrogen and phosphorus leaching into streams.
An autumn cover crop of oil radish was sown to capture excess nitrogen in the soil before a crop of spring beans, and cultivation was reduced by direct drilling the following spring wheat crop to keep the soil structure intact, minimising the loss of sediment and the attached phosphates.
Prof Kevin Hiscock of the UEA said the results were measured by 10 porous pots, with samples taken at 90cm depth, which showed the nitrate concentration under the cover crop was between 0.5 and 1mg per litre – compared to 15-18mg per litre in other fields subjected to more conventional ploughing and left over the winter.
James Beamish, Salle Farms' crop production manager, said there had also been problems. 'Everybody seems to think of cover crops as a silver bullet,' he said. 'We have had this fantastic work done by the UEA and we can see the benefits, but there has been some problems as well.
'In the first year the oil radish had a massive canopy by late November, sucking up a lot of nutrients, but last year the crop didn't really want to take off. By the end of October it was in flower so we had to come and top them to stop them seeding. The biggest problems was trying to destroy them. We sprayed them with glyphosate, but they didn't want to die.
'The really interesting thing has been the direct drilling. It's good to have a project like this to make us push our boundaries'