High fertiliser N prices are causing concern for cereal growers. The main question is whether fertiliser N rates should be reduced and if so, by how much.
The majority of growers should be reducing their N rates in 2022, but the amount is dependent on both fertiliser N cost and grain value.
The increased fertiliser N price is, to some extent, offset by the increase in grain price since early last season.
Normally, BER would be about 6. Higher BERs this season mean the N rates should be reduced
The breakeven ratio (BER), number of kilos of grain required to pay for one kilo of N, is commonly used to determine adjustments in N rates.
Taking CAN at €675/t (€2.5/kg N) and grain at €220 (€0.22/kg) gives a BER of 11.4.
Normally, BER would be about 6. Higher BERs this season mean the N rates should be reduced, the adjustment being about 6kg N/ha for each unit change in BER above 6.
In this example, the normal N rate should be reduced by 5.4 x 6 = 32kg N/ha.
The starting point should be the recommended rate given in the Teagasc Green book, not necessarily what a grower did in previous seasons
Recent Teagasc analysis suggests that the change in N rate per unit change in BER should be slightly higher than 6kg N/ha for winter wheat (6.5) and lower for barley (5).
In summary, N rates should be reduced by 25-35kg N/ha this year compared to normal and the calculated average yield loss as a result is 0.2t – 0.3t/ha.
The starting point should be the recommended rate given in the Teagasc Green book, not necessarily what a grower did in previous seasons.
This is a particularly important point for malting barley growers, who typically use less N than would be recommended for yield in order to meet protein specifications, particularly those growing distilling barley.
In many cases, malting barley growers should make much smaller reductions, if any, to their N inputs in 2022.
Urea, where it is available, has a lower cost per kg N. However, be mindful that some of the N in urea can be lost via volatilisation into the air under certain conditions.
In order to maximise the efficiency of use, avoid applying N where crop demand is low or where the risk of loss is high
This problem can be eliminated by using protected urea. Urea also has a lower bulk density than CAN-type products, making it more difficult to spread evenly on wide trams, particularly in marginal spreading conditions – great care should be taken to ensure that your machine is properly set up to spread urea.
In order to maximise the efficiency of use, avoid applying N where crop demand is low or where the risk of loss is high.
Instead, focus N applications to when N requirement is highest, which for cereals is during stem extension.
Applications early in the season should be avoided or kept to a minimum amount.
In terms of splits, where greater than 150kg N/ha is to be applied, three splits are suggested.
A lot of research at Oak Park would indicate that any effects of altering the amounts applied at different splits is limited, so applying the same percentage reduction to all splits is suggested.
