After the floods, fears grow over level of nitrogen losses

After the deluges of 2012 most of the region’s farmers could have been forgiven for thinking they would never see as challenging a growing period again.

However, following high levels of rainfall and the continued bad weather in the first months of 2013, many farmers are now concerned about the level of nitrogen losses that may have occurred.

Some advisers are recommending that more nitrogen be applied, as a matter of course, but with ammonium nitrate at around £300/t the cost of applying extra nitrogen cannot be ignored.

Nitrogen losses will mainly come from leaching but where soils have been waterlogged or even under water for long periods denitrification may also occur.

According to Sean Stevenson from analytical services specialists, NRM: “The exact extent of nitrogen losses through leaching and/or denitrification following heavy or sustained rainfall can be hard to quantify.

“It is the nitrate form of nitrogen that is susceptible to loss though leaching and denitrification so the extent of any loss is governed by the amount of the crop nitrogen supply that was in the nitrate form when the rainfall occurred.”

Other factors also influence the extent of nitrate losses, application timing, soil characteristics the type of nitrogen fertiliser and so on.

In general, leaching losses are more likely on sandy soils and denitrification more apparent on medium and fine textured soils that have poor drainage. However, the only way to be sure of how much nitrogen is in the soil is to conduct a soil mineral nitrogen test.

Mr Stevenson added: “Soil Mineral Nitrogen is the nitrate-N plus ammonium-N content of the soil within the potential rooting depth of the crop.