Grass Growth Series: Fertiliser applications on second cuts

This article is part of a Grass Growth series in association with Yara.

It’s fair to say, that first cut silage yields have been disappointing – and that’s no wonder considering the growth we’ve had during April and early May.

Some have ended up grazing fields which were intended for first cut, so with this in mind and low silage stocks, a good second cut will be more important than ever to put tonnes in the pit for the winter ahead.

If adequately fertilised, and with favourable growing conditions these second cuts crops are capable of 6 – 7t/ac of fresh grass, which isn’t far behind a good first cut. Slurry and fertiliser application rates are important considerations to make the most of second cut yield potential.

Slurry

If slurry is available, the amount needs to be evenly applied over the entire second cut area.

What often happens is, too much is applied at the beginning before it’s realised there’s not enough in the tank, and then the application rates has to be reduced or even vice versa. We end up with parts of the field being undersupplied with nitrogen (N) and potassium (K).

Slurry needs to be applied as soon as the first cut has been harvested, and preferably by low emission spreading systems (LESS) like trailing shoe. On fields that are only now being closed-up for silage after being grazed, then the grass needs to be well grazed down.

Slurry is a great source of nutrients and reduces fertiliser costs, however we don’t want the residues of this slurry ending up in the pit and causing issues. It really depends on how ‘watery’ or ‘thick’ the slurry is.

Thick slurry would need to be applied in lower volumes for fear it mats the grass and doesn’t get washed off. Lower dry matter (DM) slurry or ‘watery’ slurry can be spread at higher rates.

The period of time between slurry application and a planned harvest will also dictate the slurry rate. If it’s less than six weeks then low volumes, and if it’s ‘thick’ slurry being spread by splash plate, then it might be better not to apply, and leave till later in the season.

Fertiliser

It’s best practice to apply fertiliser a week after the slurry has been applied. If no slurry is being applied, then spread the fertiliser within a couple of days of the first cut harvest or on closing-up from grazing.

It happens regularly that nutrient applications are delayed too long, which then results in lighter crops or crops needing a longer growing period, which in turn lowers silage quality.

Sulphur (S) is an important nutrient – and it certainly merits using a fertiliser that contains sulphur on these second cuts. The response does vary according to soil type, regularity of manure applications and over winter rainfall, but the majority of silage crops do respond to applications.

With over 90% of silage samples analysed having very low selenium levels, there is also an opportunity to increase the selenium content of silage for the winter ahead by using fertiliser’s fortified with selenium like YaraMila SILAGE BOOSTER. This is most beneficial to pregnant cows and ewes.

Why ask for YaraMila SILAGE BOOSTER?

• Guaranteed Complex Compound Fertiliser (CCF) for even nutrient application;
• Perfect ratio of N:K to meet high K offtakes;
• Contains selenium for healthier livestock;
• Contains sulphur.

Second cut NPK requirement (unit/ac)

These Teagasc book values for summer applied slurry can be used:

Yara second cut fertiliser recommendation on fields with good soil fertility:

Remember, the P fertiliser rates above may need to be adjusted based on the nitrates (NAP, 2017) limits for your farm.

With the weather Gods on our side, a good second cut has the scope to make up for lighter first cut crops, but it’s important to order whatever fertiliser is required and have it ready for spreading.  

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