Chopping straw last harvest looks smarter now that fertiliser prices are going through the roof — and so does sowing covers into overwintered stubble to capture nutrients.
But even if I need a bit less of it, I have to face the same rising costs as anyone else for fertiliser, as well as all my other inputs.
There is little I can do to affect the prices of my inputs or my outputs, but I can look at what influence inputs have on outputs.
Last harvest I produced around 10t/ha of wheat with 150kg/ha of nitrogen, which cost €1/kg. If that N now costs €2.50/kg, my N spend per tonne of wheat produced will rise from €15 to €38.
Right now forward feed grain prices for next harvest are about where this year’s prices finished, so the margin from my crop of wheat will reduce by €230/ha, or about €100/ac.
I can sell grain forward for next harvest at this year’s prices but it is much harder to buy fertiliser for the spring, and €2.50/kg may well be an optimistic price.
I have been looking at work done by the Agriculture and Horticulture Development Board in the UK, where they calculate optimum N rates for a crop of wheat based on a break-even ratio (BER), which is the number of kilos of wheat it takes to buy a kilo of N.
Their standard figure of 5 was not far out in 2021 but for 2022 the number looks more like 12.
As N is applied to a crop, each extra kilo produces a smaller yield increase, and the economic optimum is defined as the point at which the value of extra grain produced ceases to exceed the cost of the extra N applied.
The BER represents the relationship between grain and fertiliser prices, and as it rises the optimum amount of N falls.
AHDB’s work suggests that a BER rise from 5 to 12 justifies a reduction in N of 70kg/ha. That sounds like a lot and it will be interesting to hear what figures are being suggested in Ireland.
This reduction will not give me the same margin on my crops that I had this year, but using any more will only reduce the margin further.
However, using less N will do more than just reduce the cost of that input.
If I aim at lower yield for maximum margin, I am also going to save on P and K, as the smaller crop will need less of them.
There will a lot less N to grow weeds too, so I can make savings on herbicides.
I don’t want my crops to be too lean and hungry, but if they are less flabby I expect there will be less disease around so here’s some more savings.
A lot less synthetic inputs on my crops is also going to give the life in my soil a boost and move it a bit closer to being able to cycle nutrients efficiently, further reducing the long-term dependency on synthetics.
It’s not easy to see cost increases as a good thing but in this case, by reducing the risk of cutting inputs, they may be the start of a virtuous cycle.
Andrew Bergin is a tillage farmer based near Athy, Co Kildare