High prices and a scarcity of urea and other products has meant that many farmers have had to have a rethink of fertiliser strategy for next spring.
Some farmers are saying that as fertiliser is so expensive, they are not going to spread early nitrogen (N) and are instead going to feed extra silage and meal to cows in spring.
Let’s examine this strategy.
The typical responses to urea (mid-January application) from a Teagasc trial carried out between 2018 and 2020 is 10kg of grass for every 1kg of N when 30kg N/ha is applied.
This is very similar to previous studies on N response in springtime.
This means that by mid-March, the fields that got the early N had 300kg more grass cover on them.
If urea costs €900/t, each kg of N costs €1.95 or it costs €59 to spread the hectare and for that you get 300kg of extra grass, so the cost of the grass is 19.6c/kg DM.
I worked it out previously that the higher prices of fertiliser next year means the cost of making a 5t DM/ha crop of first-cut silage will work out at 22c/kg DM.
Therefore, the early N is cheaper and has much higher feed value than feeding silage, which needs to be replaced next summer.
As for meal, you need to convert the price of meal in fresh weight to DM. Meal is generally 15% moisture, so one tonne of meal would want to be costing around €170/t fresh weight to be comparable to grass at €196/t DM.
So for me, it’s quite obvious that despite the high prices of fertiliser, spreading N to grow grass will give an economic return.
Of course, this presumes that the grass grown will be utilised. If this is normally an issue, then I would definitely reconsider spreading early N.
Equally, if the response is less than 10kg grass for every 1kg of N applied, then the economics will change also.
This is particularly important where there are old grasses and poor soil fertility or very exposed land or heavy soils.
In such situations, the responses are unlikely to be as good.
Farms on good ground
For those on good ground, the following advice will help to ensure a good response.
For farmers who normally spread N by early February, the decision not to spread any N this year (either in slurry or chemical form) could be a costly one.
Across a 40ha farm, 30kg N/ha either through slurry or fertiliser will grow 300kg of grass per hectare by mid- to late-March.
That’s 12t DM of additional feed grown at a cost of €2,340 in fertiliser costs only.
To buy the equivalent DM in meal would mean the purchase of 14t of fresh weight meal, which at €320/t would cost €4,480.
I fully agree with the principles of being conservative with N, but the risks of losses from spreading small quantities of urea-based N in spring is small.