Grass advice: Time to change the mindset; time to think silage

Actions and decisions made now will determine the quality and quantity of silage in next year’s pit and bales.

As some farmers start the second rotation, we switch from following the spring rotation planner to looking at the wedge and identifying which surplus paddocks can be closed for silage.

To maximise silage quality, paddocks need to be identified early and closed by the middle of April to be cut by the end of May – before the development of a seed head.

The chances of being able to harvest a third cut of silage will be determined by the weather and the first cut cutting date – in mid-to-late May.

Additionally, if you have silage ground still to be grazed by the end of the month, the best thing to do is leave it, close it up and fertilise it for silage.

It is not essential for silage ground to be grazed before being closed up for silage, particularly if it got a tight grazing in the last round in autumn or early winter.

Nitrogen (N)

The Fertilizer Association of Ireland advises to spread 80 units/ac (100kg/ha) of N for permanent pasture and 90 units/ac (110kg/ha) for reseeds; to allow 2 units/day from application date to cutting date.

It is important not to forget about sulphur (S) when applying fertiliser. S should be spread at a rate of 20 units/ac (25kg/ha) for each cut of silage.

Phosphorus (P) and potassium (K)

Silage swards have a higher P and K demand than grazed swards due to the herbage offtakes.

The trick for managing P and K applications for silage is to remember – what comes off must go back.

For slurry applications, 3,500 gallons/ac of thick slurry or 7,000 gallons/ac of watery slurry is needed for P and K maintenance. Slightly lower applications of chemical fertiliser and slurry is needed for the second-cut.

Taking paddocks out for bales

It is important to take note of where surplus bales are being taken off throughout the grazing season. Often times replacing the P and K taken off is forgotten about and these paddocks end up becoming low in P and K indexes.

According to Dr. Stan Lawlor (head of specialty business in Grassland Agro) for every 1,000kg of DM/ha cut for bales – rather than grazed – will add approximately 2.5kg/ha of P and 25kg/ha of K to the overall P and K requirements for maintenance to a paddock across the year.

The most efficient way to replace this P and K offtake is to target slurry to those fields cut for bales. For four bales, 700 gallons/ac of thick slurry is needed or 1,500 gallons/ac of watery slurry.