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.

Flooded farmland
Flooded farmland

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.

“When estimating the total amount of N that will come from the soil – that’s the Soil Nitrogen Supply (SNS) – you also need to include an estimate of the N already in the crop and an estimate of the mineralisable soil N. A test is also available from NRM to determine this mineralisable value.

“Once you have your SNS index you can use The Fertiliser Manual (RB209) to determine the correct fertiliser nitrogen recommendation.”

The heavy rain of last year has already resulted in a huge reduction in the amount of crops harvested, with levels of fruit and vegetables successfully grown also significantly down on previous years.

The overall cost to the rural economy is thought to have run into the billions, with diminished tourist and visitor levels a major driving factor.

Bed and breakfasts and holiday cottages all saw a fall-off in trade.

Last year also saw a great number of the region’s agricultural shows having to be cancelled due to waterlogged showgrounds.

The country’s premier agricultural event the Great Yorkshire Show had to close after the first day due to the rain, with organisers having to refund trade-stand holders at a hefty cost.

Bosses are keen to make sure the show is weather-proofed this year by investing heavily in extra drainage and roadways, with the society also aiming to acquire more car parking.