Multi-cut silage systems

Multi-cut systems involve cutting grass earlier and more frequently than in standard silage systems; this can increase forage yield and quality. Find out how to optimise grassland productivity by following a nutrient management plan.

Applying nitrogen (N) fertiliser at the right time will stimulate grass growth and help maintain silage quality. This is particularly effective for swards with a high proportion of perennial rye-grass, which use nitrogen more efficiently than other grasses.

However, it’s important to strike the right balance.

Too much nitrogen can produce grass with low sugar, leading to silage with high ammonia and butyric acid levels, which is less palatable for livestock.

Too little nitrogen will reduce yield and protein levels may be too low to meet the nutritional requirements of livestock.

Nitrogen recommendations for grass silage cuts are detailed in Table 1.

For more in-depth information on nitrogen management and recommendations, refer to Section 3: Grass and forage crops of the Nutrient Management Guide (RB209).

Table 1. Nitrogen (N) recommendations for grass silage cuts (kg/ha)

To determine accurate application rates for phosphate (P) and potash (K), you’ll need a recent soil analysis showing the soil index.

Fields cut regularly for silage tend to have higher requirements for P and K, as these nutrients are heavily removed by the crop.

For example, a 30% dry matter (DM) silage contains approximately 2.1 kg of P and 7.2 kg of K per tonne of fresh material.

For multi-cut systems, the application of K is critical for sustained productivity. If your soil analysis shows soil indices of 2+ or lower, you will need to provide additional K.

As part of a three-cut system, it is recommended to apply an additional 30 kg K/ha after each cut.

Table 2. P and K recommendations based on soil index results (kg/ha)

For more in-depth information on P and K recommendations, refer to Section 3: Grass and forage crops of the Nutrient Management Guide (RB209).

Sulphur (S) deficiency has become more common in grassland, especially in the later cuts of a multi-cut system and in fields receiving high nitrogen rates.

Symptoms of S deficiency include yellowing of the youngest leaves, which not only reduces grass yield but also impacts nitrogen uptake and protein formation in plants.

Soil testing is not sufficient to determine sulphur levels. Instead, you should test the sward just before cutting – this will help you determine S requirements for subsequent cuts.

Plants use S during the growing phase, which means it’s too late to address a deficiency close to harvest.

An S concentration of less than 0.25% total S or an N:S ratio greater than 13:1 in the grass dry matter (DM) indicates a deficiency.

• Sandy, shallow soils
• Loamy and coarse-silty soils in areas with >200 mm rainfall from November to February
• Clay, fine silty or peat soils in areas with >400 mm rainfall between November and February

For soils at risk of sulphur deficiency, apply 40 kg SO₃/ha before each cut to optimise grass growth.

Fertiliser availability: Ensure fertilisers are available for application within the first week post-harvest for maximum effectiveness.

Timing of nitrogen application: Grass responds best to nitrogen when soil temperatures, measured at a depth of 10 cm, are higher than 5.5°C for at least four consecutive days.

Organic manure management: Organic manures, such as slurry or farmyard manure, should be applied at least six weeks before silage to avoid contamination that can cause fermentation problems. Ensure grass has enough time to use nitrogen from manures before fertiliser applications.

Grassland nitrogen: Under optimal weather conditions, grassland can use 2.5 kg N/ha/day (around 2 units of N/acre/day).

Soil testing: To manage fertilisers and manures effectively, test soil every 3–4 years. This will help you make the most cost-effective decisions for your grassland.