Fertiliser application on winter cereals will be the priority on tillage farms this month.

It is now recognised that the dramatic increase in fertiliser costs will result in an adjustment to application rates this season.

Teagasc advises that recent soil test results and a nutrient management plan are essential to target fertiliser use. The economic optimum nitrogen (N) rates are reduced by 20-35kg/ha depending on crop type, grain value and N cost.

Efficient use of N fertiliser

Making the most efficient use of applied N is crucial, so target application to match crop requirements and ensure soil conditions are good to avoid leaching losses.

Phosphorus (P) and potassium (K) need to be applied to match offtakes, but it may be uneconomic to apply P and K for build-up in 2022.

A 10t/ha crop where the straw is removed will require 38kg of P and 100kg of K or equivalent of 4.25 bags of 10-7-20/ac.

Winter barley crops should receive the first dressing of N (50kg/ha) in early March. The main split should be applied by GS31.

On thin or backward crops, the first N can be earlier (start of growth) but application rate should be low as crop demand is small.

Sulphur (S) (15kg/ha) and deficient trace elements (based on soil analysis and field history) should be applied before GS31.

According to Teagasc, most barley crops received a herbicide last autumn. But where a tidy-up application is required, growers should use a sulfonylurea, depending on weeds present. It is too late to control annual meadow grass.

Winter wheat crops should receive 40-50kg/ha of N as the first split in mid March or by GS30. Application rates should be increased 75kg/ha for thin crops, second wheat or where take-all is a risk.

Splits

Growers should divide N applications over three splits as follows: One quarter; half; one-quarter.

 The main dressing should be applied by GS31 and the last split by GS39.

Where grass weeds are present, Pacifica Plus/Monolith plus Biopower are options. Broadway Star plus Torpedo is a strong brome option where annual meadow grass has already been controlled.

The first application of approximately 50% of the total N requirement should be applied to winter oat crops by GS30 (early to mid March).

Many winter oilseed rape crops have large canopies this season and as a result there will be large savings on N. A green area index (GAI) of less than 1.0 will require a dressing of 225kg/ha of N as soon as growth starts.

In contrast, crops with a GAI of 2.0 will only need a 130kg/ha application, which can be delayed until mid-March.