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Cornish farmers urged to take soil temperatures and clean up swards to maximise spring Nitrogen.


With spells of warmer and wetter weather becoming the norm, relying on T-sum 200 to assess the right time to apply nitrogen may no longer be the best approach, says independent grassland adviser to CF Fertilisers, Dr George Fisher.

“Although there’s no need to panic, as there’s a two-week window around the optimum where you’ll get at least 90 percent of the response to the first application of fertiliser Nitrogen, it makes sense to take the temperature of your soil yourself with a soil thermometer placed down 10cm into the soil.


George Fisher- independent grassland specialist“When the temperature steadies between 5-6 degrees centigrade over a few days, and the forecast indicates no hard frosts to come, that’s the green light for your first application,” 

Dr George Fisher Independent Grassland Specialist.



“When the temperature steadies between 5-6 degrees centigrade over a few days, and the forecast indicates no hard frosts to come, that’s the green light for your first application,” says George.

“At this level, your nitrogen window is open, and applying at this point means you are optimising the nitrogen’s efficiency.  In fact, applying within this period means utilisation is more likely to be 90 percent, as opposed to just 60 percent, when too early or too late outside this time span.

The T-sum 200, which is the culmination of air temperature since January 1, has long been a barometer used in assessing soil temperature, but George explains that if you’re not catching this two-week window right, you’re throwing money away.

He explains that the T-sum is more often out of kilter with what’s happening in the soil when compared to the outside air temperature – especially as milder and wetter winters are becoming increasingly common.

“The important point is to get the nitrogen into the soil at the time when grass roots are able to respond - activating the roots, and waking up the plant. When the application’s too early, there’s a risk of run off or leaching, and when it’s too late, the opportunity to get the most out of your operation is lost.  T-sum is an indicator of soil temperature, so why not be more accurate and measure soil temperature itself?”

Hefin Llwyd, farm adviser with CF Fertilisers, adds some advice for managing spring grassland coming out of an unusually wet and mild winter.  “There are very good grass covers around at the moment, so we are being asked a lot how to handle these.  If the grass doesn't get taken by late frosts, my advice would be to fertilise post grazing to make sure that swards get ‘cleaned up’. Soil temperature will be low for a while, and the first N application will be better utilised if the soil temperature is rising and the grass plant is actively going through its vegetative stages, and hunting out N and P through the roots.

“It’s been such a mild winter and we need to adjust management, so plan to apply fertiliser at the right time by soil temperature, but get an early grazing in first if you can to clean-up and have a fresh start.   Also, if covers don't get taken down sufficiently,  then it’ll lead to grazing issues later in the spring and through summer, so get swards cleaned up when conditions allow and fertilise at the optimum time with the right rate.

“This spring, above all others, farmers must look at using the best quality fertiliser to get the best response… and this is where our 50 years of results from the British-manufactured Nitram® and true granular compounds will give growers confidence that they’re starting at the right place in terms of building business profitability through grass yield and quality.”

George adds that with milk prices not improving through the coming season, farmers will be cautious with the level of inputs they use this spring.  “Using a quality fertiliser of the right analysis for your system requirements will be key, as well as making sure application timing and rates are right, in order to maximise both quality and yield.”