Fertiliser price is going to affect silage plans this year. With CAN over €700/t and a lack of merchant credit, many farmers are simply not in a position to buy nitrogen.

Where farmers have already secured fertiliser for silage, many are considering reducing application rates for the first cut with the aim of stretching nitrogen stocks into the summer. This is understandable, given that nitrogen prices are likely to keep rising if the availability of fertiliser becomes a problem.

Before closing off fields for first cut in early April, think carefully about how much nitrogen will be applied to silage swards.

Grass growth in May and early June will hit peak levels. So it is important to maximise the amount of grass grown during the six to eight week window before harvesting.


If farmers are planning to reduce stock numbers ahead of next winter, reducing silage fertiliser rates is fine as forage requirements will be lower.

But if stock numbers remain unchanged, and it is unlikely that existing silage stocks will carry over to next winter, then farmers face a potential fodder shortage.

This means either buying additional silage, or feeding more concentrate, to bridge the fodder deficit and it will come at a cost.

Example farm

Take an example suckler farm carrying 40 spring-calving cows over winter, plus 20 weanlings held over and sold each spring.

Cows are normally housed for six months from mid-October to mid-April.

From housing to mid-March, dry cows eat 1t/head of silage each month.

In the last month before turnout, cows have a calf at foot and eat 1.5t/head. Total silage requirement for cows is 260t.

Weanlings average 0.75t/month of silage from October to selling in mid-March, adding another 75t to feed demand.

Factoring in a 5% safety net for early housing or late turnout, and 5% for waste forage, the farm needs to conserve around 370t of silage.

The farm operates reasonably productive ground with index 2 soils for P and K. Outlined are some scenarios on the impact of silage yields depending on fertiliser applications.

  • Option 1: go with normal fertiliser rates.

    First-cut silage is harvested on 30ac with three bags of CAN/acre applied along with slurry. Taking CAN purchased at €725t, fertiliser costs come to €3,263 for 4.5t applied.

    First cut is harvested on 1 June at an average 9t/ac freshweight, leaving 270t of grass in the pit. Grass is harvested on time and silage quality is 70 DMD.

    The farmer now needs to save 100t of silage to cover forage demand for the six-month winter, including the safety net and waste allowance.

    If second cut is made in early August, at a typical yield of 7t/ac, only 15ac of the silage platform needs to be closed up. The other 15ac can be used for grazing from June on.

    The 15ac at 2.5 bags/ac is another 2t of CAN (€725/t), bringing total fertiliser costs for first and second cut to €4,713.

  • Option 2: reduce fertiliser and target same cutting date.

    In this option, silage is harvested on 1 June but only two bags/acre of CAN are applied across 30ac, costing €2,175.

    But with less nitrogen applied, yield is reduced to 7t/ac freshweight. This means 210t of silage is in the pit, leaving 160t required to maintain stock over winter.

    If second cut gets two bags/acre and yields 6t/ac freshweight, 27ac of grass needs to be closed up.

    At the outlined fertiliser rate, another 2.75t of fertiliser is needed, bringing total fertiliser costs to €4,169.

  • Cost difference

    There is an initial saving of €544 on fertiliser with this option.

    However, the contractor costs from harvesting an extra 12 acres in second cut at a hypothetical €120/ac costs €1,440, meaning the farmer is €896 better off in option one. In addition, as less silage ground is available for grazing after first cut, this is another downside to keep in mind.

  • Option 3: reduce fertiliser and cut two weeks later.

    In the third option, the farmer follows the fertiliser rates in option two, but delays harvesting first cut for a fortnight to increase yield. Again, fertiliser cost across 30ac of first cut is €2,175. With the delayed cutting, assume yield is back at 9t/ac freshwight, giving 270t of grass ensiled.

    This means 100t is needed in the second cut. But the later cutting date will slow regrowth, meaning second cut is unlikely to be cut before late August to early September.

    At 5t/ac yield for second cut, 20ac has to be closed up. This requires 2t of CAN, bringing total fertiliser costs to €3,635, giving a fertiliser cost saving of €1,088 over option one.

  • Hidden costs

    However, the extra five acres harvested would amount to a hypothetical €600 in extra contractor charges, bringing the cost saving down to €488.

    Delaying first cut by two weeks can increase yield, but the extra bulk has little feed value as it will be seed heads and stem.

    Therefore, the DMD of mid-June silage is likely to be around 64 DMD compared to 70 DMD for the first-cut silage in option one.

    Weight gain

    On 64 DMD silage, the 20 weanlings will require an additional 1.5kg/head/day of concentrate to match the weight gain of the weanlings on 70 DMD silage in option one.

    Over 150 days, this comes to 225kg/head or 4.5t of concentrate. For a ration costing €375/t, this comes to €1,687.

    Even if the ration was reduced to 1kg/day, this still comes to an extra 3t of concentrate fed.

    Either way, the €400 saving on fertiliser is wiped out.


    The scenarios set out are hypothetical and intended to get farmers thinking about the most cost-effective option to ensure there is enough forage on farm next winter.

    Aim to maximise the grass grown on farm during May and June for silage. Fertiliser rates should be tailored to suit this.

    Ultimately, decisions will be based on affordability, just ensure that short-term cost savings do not become a long-term expense.

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