Where to now for fertiliser applications?

The summer’s drought not only resulted in grass growth rates plummeting, but it also curtailed fertiliser applications on many farms.

Serious soil moisture deficits (SMDs) forced many farmers to retire the spreader to the shed for a number of weeks.

However, now that the rain has finally made its much-needed return, farmers may be questioning what rates to apply to boost grass growth rates for both grazing and silage swards.

After the rain that fell over last weekend, Teagasc recommends applying 27un/ac of nitrogen (N) to kick start grass growth. Ideally, this should be applied immediately while moisture is still available.

It’s also advisable to spread phosphorous (P) and potassium (K) compounds – enriched with sulphur (S) – where the fertiliser plan allows.

When it comes to planning an additional cut of silage, the advisory body recommends the application of 50un/ac of N now. Depending on grass growth rates, an additional 20un/ac may be applied in 14-21 days. However, this depends on growth rates.

Table source: Teagasc

Where silage crops are ready for harvesting, Teagasc has noted that N readings are high and it advises farmers to wilt the grass for at least 24 hours before picking up. Wilting will increase dry matter and sugar content, thus overcoming high N levels.

As many farmers are facing a fodder deficit this winter, Teagasc also outlines that lowly-stocked farmers should harvest surpluses and consider growing a second/third-cut silage crop. Forage will be in demand for the winter of 2018/2019 and this will be beneficial for both lowly and highly-stocked farmers.

Applications following cutting/grazing of second-cut silage

Teagasc also offers advice on fertiliser programmes following the grazing or cutting of second-cut silage ground.

Key advice:
  • Apply slurry with a trailing shoe on land that was cut for second-cut silage;
  • Remember, many second-cut silage yields were low (or grazed) and, as a result, there will still be a large proportion of N, P and K in the soil following fertilisation after first-cut silage;
  • Once rain has been received, take the chance to spread fertiliser and aim to take a third cut of silage;
  • The level of fertiliser application will depend on:
    • Whether a paddock was cut for silage or grazed (paddocks cut will need compounds high in P and K);
    • The yield of grass cut/grazed for second-cut silage (higher yield, higher fertiliser requirement);
    • The amount of unused fertiliser in the soil (estimate from silage yield, the amount of fertiliser applied for second cut and the amount of rainfall since fertiliser was last applied);
    • Adjust fertiliser rate depending on soil N mineralisation.