Getting nutrients out on first-cut silage ground will become a priority on many farms over the coming days and weeks as many farmers will aim for a first-cut from around the middle of May onwards, depending on growth.
With this in mind, the best approach is to get nutrients out early so that you are not held delayed in cutting.
In terms of nitrogen (N), grass silage will take up on average 2.5kg/ha/day of N (2 units/day), which means N should be applied at least 50 days before cutting to ensure full crop N utilisation.
Ideally, you don’t want to be cutting this tight, as the middle of May might arrive and the grass could be fit to cut with an abundance of quality but you could be restricted due to N not being utilised.
Farmers need to harvest quality silage, so it can be fed to milking cows during the shoulders of the year or for winter milking cows.
The target should be to cut silage with a dry matter digestibility (DMD) of 72% and in order for this target to be achieved, silage should be cut closer to the middle of May.
With dry conditions of late, many farmers have been targeting silage ground with the thicker slurry in the yard and spreading more diluted stuff on the grazing block.
First-cut silage
Farmers should start by completing 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.
The budget should be based off what the normal housed period is on your farm, and farmers should add an additional supply of about 10% to allow for a bit of comfort.
By knowing the amount of silage you will need, it will allow you to calculate how many acres will be needed to achieve this, and in many cases three cuts are factored into this.
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.
What nutrients does a crop of first-cut silage require?
- 100kg N/ha or 80 units/ac;
- 20kg phosphorous (P)/ha or 16 units/ac;
- 125kg/ha or 100 units/ac of potassium (K), to total 90kg prior to cutting and 35kg after silage has been cut;
- 20kg of sulphur (S)/ha or 16 units/ac.
These rates are based on soil P and K indexes of three, as P requirements double to 40kg/ha or 32 units/ac if in index one and K requirements go up to 175kg/ha or 140 units/ac if index one.
3,000 gallons/ac of good quality cattle slurry of 6% dry matter (DM) will supply sufficient P and K levels and about 30kg of the N requirements to grow a crop of grass silage, but a hydrometer should be used to see if the slurry is of a good DM.
Any fertiliser applications should be held off for a week after slurry was applied which means if there is no slurry out yet and you intend to use it to make up your P and K levels, the tanker should be going out in the coming days.
If this is achieved, then urea and S can be used to make up the remainder of the N requirements.
If there is no slurry spread on the farm, then farmers could spread a product like 13-6-20 at about three bags/acre followed by about 1.6 bags/acre of urea or protected urea + S.
If your soil is index one or two for P and K, then 3.5 bags/acre should be spread of 13-6-20 followed by a bag/acre of protected urea + S to make the N requirements.
Ideally, your P and K levels should be made up through slurry which will leave you to make up the remaining 70kg of N/ha through spreading 1.5 bags/acres of protected urea + S.
