With the cost of bought-in feed soaring, homegrown silage is an obvious choice to reduce reliance on purchased feedstock to meet target milk yields. However, it’s essential that the silage quality is optimised through multiple factors including calculated fertiliser use and considered cut timings. Make sure you’re informed ahead of this silage season by reading our top tips below:
Use soil analysis to inform inputs
To optimise grass growth and quality, it’s recommended that soil nutrient tests are carried out and analysed before adding inputs to silage fields.
Soil pH and lime status affect how well nitrogen is utilised by the sward so the results can be used to make sure the right input is applied at the right time.
Nitrogen application needs to correlate with the timing of the first cut and with subsequent cuts during the season. Aim to apply nitrogen at least 50 days before the expected cutting time to ensure full crop utilisation. It should also be applied at a rate that is adequate for grass growth but not so high that it’s wasted. Bear in mind that grass silage will take up to an average of 2.5kg/ha/day.
Pre-cut grass testing is key
Due to variations in weather and growing conditions year on year and regionally, it’s important not to base cutting decisions solely on the previous year’s harvest date. Instead, take weekly grass samples, starting around three weeks before the grass is expected to be ready.
Grass sample reports will provide details of the nutrient composition of swards, specifically:
- Neutral detergent fibre (NDF)
- Dry matter (DM)
- Free nitrate levels
- Protein levels
- Sugar content
Taking samples at least every week will indicate how the levels change which will inform the optimum cutting time to maximise forage quality and fibre digestibility. Pre-cut testing should continue to be carried out until at least the third cut to determine the cutting time.
Farmers in Cumbria can keep an eye on the weekly grass monitor reports posted on our social media channels for an overview of how the grass is changing throughout the silage season, which will also help to inform decision making.
On-farm specialists can take samples and send them for laboratory analysis, or they can provide bags for samples to be taken. Check out our video below on how to take a grass sample:
Critical cut timings
Milder weather over winter or in early spring can bring the optimum first cutting date forward and conversely, colder weather conditions can delay it. Decisions on when to cut grass for silage should continue to be guided by pre-cut sampling results.
Silage should be cut when the NDF is between 38% and 42%. A rise in NDF of around 5% above target level can lead to a reduction in metabolisable energy (ME) of up to 1.6 MJ per Kg/DM in the silage.
If grass is cut at the optimal NDF level, energy levels in the silage will typically be higher, which will reduce the amount of bought-in feed required to meet energy requirements for milk production. The correct NDF level is also needed for good rumen function as levels exceeding the target can slow digestion and reduce intakes, impacting milk yields.
|Sugars (%)||Minimum 3% in fresh weight (10% in DM)|
|Free nitrates (DM)||>1,000mg/kg in fresh weight|
|NDF (% DM)||38-42%|
|DM (%)||18% at mowing
30% for clamping
35-45% for baling
Top tip: If the free nitrate level is too high then, even if the NDF has reached the right stage for cutting, hold off cutting for a short while to avoid a negative impact on the fermentation process.
Consider the number of cuts
The number of cuts is very specific to each farm and its aim for quality and yield, so a multi-cut system may not be suitable for all farms. Think about the farms’ overall objectives, milk contract, silage plan, field locations and length of ley when considering how many cuts to take.
It can be tricky to get the nutrient balance right throughout the season but keep in mind that silage making and fertiliser programmes should always match the grass varieties on-farm and the desired number of cuts.
If you require assistance before or during silaging this year, contact your local on-farm specialist.