Although there are still many cows in the shed, and grazing has not fully taken off yet, it’s now time for silage preparation to begin.

The harvesting of first cut silage will hopefully be taking place on most farms in early to mid-May if conditions and grass growth allow.

Most farms will be aiming for the first cut of silage to be as high in quality as possible, so that it can be used as milking cow feed during the shoulders of the year, or for cows who are milking during the winter months.

The target should be to harvest silage with a dry matter digestibility (DMD) of 72%. In order for this to be achieved, it needs to be harvested before May 26.


The first job that needs to be completed, is determining how much silage is going to be needed for the 2024/25 winter.

Current silage supplies should be considered to determine if much will be left over and can be carried into next winter.

You should complete a fodder budget to determine the needs of the farm based on the number of cows, replacement heifers and non-replacement animals, such as bulls.

Base the budget off what would be the normal housed period on your farm, and add an additional supply of about 10%.

Once you know how much silage is required, you should be able to calculate how many acres will be needed to achieve this – remember you could be harvesting as many as three cuts.

You ideally want around 50% of the total silage harvested to be high quality or milking cow feed, and the remaining 50% to be dry cow feed.


Once the total area that needs to be closed for silage is determined, you then have to start determining the amount of fertiliser you will need.

Fertiliser requirements for a first-cut silage crop:

  • 100kg N/ha or 80 units/ac;
  • 20kg P/ha or 16 units/ac;
  • 125kg/ha or 100 units/ac of K, to total 90kg prior to cutting and 35kg after silage has been cut;
  • 20kg of S/ha or 16 units/ac.

A good portion of the fertiliser requirement can come from your slurry.

Using a 6% dry matter (DM) slurry at a rate of 3,000 gal/ac will make up nearly all of the phosphorus (P) and potassium (K) requirements and a third, or 30kg of the N requirements.

This means urea, or protected urea and sulphur (S) can then be used for the remaining N requirements of 70kg/ha.

When fertilising silage crops, you should spread the slurry first and then the urea or protected urea with S about a week later.

Where slurry is not available, farmers can use a chemical fertiliser such as 10-5-25 at a rate of 3-3.5 bags/ac.

This will supply all the P and K for the crop at closing, but if this is being used the crop needs to be topped up with N. This can be the same form of urea or protected urea and S.