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Grass silage being cut

Making silage of high quality will ensure good daily weight gain on weanlings, cut down on meal input for finishing cattle and also increase milk output in dairy cows. The decisions made in the next number of weeks on farm will determine the cost of production for up to 6 months next winter. Nearly all silage paddocks have been closed off at this stage. The harvesting date will depend on the closing date, the date and rate of fertiliser application, contractor availability and of course the weather.

It takes about 6 to 8 weeks for grass to mature to an optimal stage for cutting. As a general rule, allow for 2 units of nitrogen (N) to be used per day, but it is recommended that you test the N levels in the grass before you cut. If there is N that hasn’t been used, it can affect the fermentation ability of the crop. Aim for an N level of 0.1% or less and sugar levels over 3%.


Cut, Wilt and Pit

Cutting silage at the correct growth stage is the most important factor when it comes to silage quality. Once seed heads begin to appear the dry matter digestibility (DMD) is about 70%, and this will drop by 1 percent every 2-3 days after that. Lodged crops with dead material at the base will have 3-4% lower DMD. To maximise quality, cut from mid-late May rather than into mid-June.

Aim to wilt grass to about 27-30% dry matter (DM), this will help achieve good preservation. In suitable weather conditions, tedding out for 24 hours is the recommended approach, grass will not dry enough in large rows even if left for 36 hours.

Ensure careful pitting to minimise dry matter losses post ensiling. These losses can be a combination of effluent losses, failure to fully seal pits, and damage to bales. Seal pits quickly and completely and monitor regularly for damage by vermin.


Alternative Fertilisers for 2nd Cut

With the focus on reducing chemical fertiliser use on farms the Terra product range offers a great opportunity to achieve the same growth with lower N application. The Terra product range is a perfect option for 2nd cut fertiliser application. The physical characteristics of Terra fertilisers are the same as any other of our fertiliser products. It has the same density, spreading ability and high quality. Typically, these products will allow for up to 20% reduction in N use, while providing the same yield due to increased N uptake and efficiency.

After cutting silage is an ideal time to look at ways to improve your soil health. Apply lime one week after cutting silage and before closing for a second cut. It’s important to note, applying lime to heavy covers of grass intended for silage can reduce the silage quality if the lime is not washed off the grass by rain.

Cattle slurry is the most common manure applied to silage fields and can vary in nutrient content depending on its dry matter (DM) content. Pig slurry is also imported on a number of farms, and it has a much higher N content than cattle slurry, while cattle slurry would have a higher K content. To get the best value of your nitrogen, use LESS system.


Nutrient value of cattle and pig slurry

  Available P & K per 1,000 gallons applied
Manure Type N P K
Cattle Slurry 7% DM 9 5 32
Dilute Cattle Slurry 3.5% DM 8 3 15
Pig Slurry 4% 19 7 20

Source: Teagasc



Sulphur (S) is just as important for silage crops as it is for grazing. The standard nutrient requirements for a crop of first cut silage are 100-20-90-16 (N-P-K-S) units/ac. Our recommendation is to apply S little and often during the growing season. Annual applications are needed as there is a difficulty in building up a store in the soil once a deficiency has been identified.



Silage time is a very busy and pressurised time on farms. It can also be an exciting time for younger family members who like to see large machines in operation. This is a dangerous combination. Keep all non-essential people well away from yards and working fields. Have traffic plan in place and place warning signs at exits to public roads. All machinery operators must drive with care and have respect for other road users. Make sure silage pit walls are not defective, do not overfill the pit and insert safety rails to indicate the location of sidewalls.


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