All tillage farmers will be aware of the recent hikes in fertiliser nitrogen (N) prices and the impact this will have on crop margins.
So, with the spring months looming, the question on every grower’s mind will be: what is the optimal amount of fertiliser nitrogen to sow on cereal crops during 2022?
According to Teagasc, cereals are very responsive to N. In essence, the amount of N applied to a crop is based on the fertiliser N curve.
Yield increases as more N is applied until a point is reached on the curve where there is no additional yield from extra N applied. This is the maximum N rate.
Teagsc advisors are also pointing out that N response curves are constructed over time and there are large variabilities between sites and seasons.
Along the N curve, and before the maximum N rate, a point will be reached where the value of the extra grain produced ceases to exceed the cost of the extra N applied. This is known as the economic optimum.
This is the fertiliser N rate, which gives the maximum profit from N use.
There is a clear distinction to be made between the economic optimum N rate and the N rate that gives maximum yield.
The economic optimum N rate is dependent on both grain price and N fertiliser cost. As the N price goes up and/or grain value goes down, the economic optimum N rate decreases.
The ratio between fertiliser price and grain price is known as the break even ratio (BER).
Again, according to Teagasc, the change in BER this season (>10) compared to last season (<4) means that the economic optimum for wheat and barley has changed.
Based on this change, the economic optimum for this season is 20-30kg/ha lower than last season. Because of lower N rates, growers can expect yields to reduce on average by 0.2-0.5t/ha.
However, despite the lower yield, the crop is more profitable by applying less N.
Tillage season planning
The January issue of Teagasc’s Tillage Newsletter discusses this and a number of other topical issues, all of which will have a direct bearing on the crop husbandry decisions taken by growers over the coming weeks and months.
Teagasc tillage specialist, Ciaran Collins, the editor of the newsletter, confirmed that planning for the season ahead has never been so important but never so difficult.
He explained:
“Input costs have increased significantly, particularly fertiliser, but machinery running and plant protection product costs have increased as well. Preparation of a crop budget is essential, as a poor-yielding crop may not cover its costs.”
“The first step in managing fertiliser this season is the preparation of a nutrient-management plan for the farm, and the first step in any nutrient-management plan is up-to-date soil tests.
“Phosphorous and potassium can be omitted at Index 4 on all cereal crops.
“Growers should also ensure that soil pH levels are correct to optimise nutrient uptake.”