20 May 2025

Silage cutting: Wilting, nitrogen and sugar levels

Silage quality has a major impact on the overall profit of the farm, but some farmers fear earlier cutting due to the presence of nitrogen in the crop.

Stephen O’Callaghan, a B&T Drystock Advisor in Teagasc Mullingar, shares some key tips to take advantage of the recent spell of good weather, allowing you to harvest your first-cut silage earlier.

Many farmers fear cutting silage early, as there may still be nitrogen in the crop. As a general rule of thumb, the crop will use up 2 units of nitrogen per day; if 80 units were applied, this should be used up after 6 weeks. If in doubt, bring a sample to be tested, Teagasc advisory offers a testing service for grass sugars and nitrogen.

The importance of sugars

High sugar content allows the crop to ferment quickly in the pit/bale, reducing pH and preserving the crop correctly. If sugars are over 3% then the crop will ensile readily; at 2-3% wilting will be beneficial. Even where there may be some level of nitrogen in the crop, high sugars and wilting will still ensure well preserved silage. If possible, mow in the evening when sugars are highest.

Wilting

Under good ensiling conditions, there is no clear benefit to using additives such as inoculants. Where wilting is likely to be of benefit, reaching the target dry matter (DM) of 28-32% is a function of swath type and duration of drying. Dry matter will not increase sufficiently in large rows (>3 metres), even if left for 48 hours. Grass tedded out and left for more than 36 hours in good conditions may become too dry (>40% DM) for pit silage. There is no advantage to wilting beyond 32% DM as preservation and dry matter digestibility (DMD) will decline.

Table 1: Impact of wilting time on crop dry matter

Keeping safe

As we enter this busy period of silage, slurry and more, it is extremely important that everyone keeps safe given the dangers present on farms. Machinery is the biggest cause of farm accidents, and farmers need to be aware that blind spots exist around vehicles where the driver’s view is obstructed.

Give consideration to where vehicles and persons may be, particularly children. Implement segregation measures between vehicles and persons, particularly in and around farmyards. Speak positively about injury dangers to children and young persons. They gain their safety values from adults. Speak to your machinery contractors about safety on your farm.

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