In the space of a short few weeks, we have gone from feeding silage to making it, with mowers, balers and harvesters becoming an ever-increasing sight on the roads as they travel between farms. While the focus on silage quality has improved in recent years, there is still some work to be done on farms.

Silage analysis results indicate an average DMD of 66%, with the assumption being that “better” farmers making higher-quality silage are more likely to test their silage. As a result, we can assume that the average block or bale of silage is even lower in DMD value.

At 66% DMD, even dry suckler cows or store cattle would just be able to source enough energy from this silage to maintain body condition. Listed below are some of the ways in which silage quality can be improved.

Fertiliser application

The application of fertiliser on silage crops was delayed for many farmers this year due to the wet weather conditions. While normal application rates of 100kg N/ha are recommended, many farmers decided to apply a reduced rate of 80kg N/ha, choosing to harvest a lighter crop at the same time as normal. When calculating nitrogen (N) application, any organic N in the form of slurry or farmyard manure also needs to be accounted for.

Spring or summer application of cattle slurry with a splash plate will provide 6 units per 1,000 gallons and 3 units per 1,000 gallons respectively, while using a trailing shoe or dribble bar will increase the N usage to 9 units N/1,000gal for spring and 6 units/1,000gal for summer. Insufficient N application will result in stunted growth or grasses going to head due to stress, lowering the silage quality. Overloading swards with N will result in lodging.

Phosphorus (P) and potassium (K) are also critical as depleting these on an ongoing basis from soils will lead to poor silage crop yields. Soil sample analysis should be undertaken every three years, with the results tailored to a nutrient management plan and fertiliser application. As a rule of thumb, removing a grass crop off a field will remove 4kg P and 25kg K per tonne DM of grass.

When to cut

As mentioned, farmers reduced their application of N this year so as not to push back their cutting date past late May, as many of the perennial grass varieties sown have a heading date of late May/early June.

As a general rule, swards will utilise 2 units N/day, although this is very variable. Reseeded swards (0-3 years old) will have a 25% higher N demand compared to older swards. The higher the grass growth rate, usually seen in the latter stages of growth when the grass has the highest amount of leaf matter, will also see increased N use.

While many farmers stringently use the “2 units per day” rule, leaving 50 days between application and cutting, the only accurate way to assess nitrogen levels in the sward is through testing the grass, usually completed by your co-op or agri-adviser. High nitrate levels in cut grass will increase the silage pH, leading to poorer preservation.

Silage testing will also reveal the sugar content of the grass, with lower nitrate levels generally leading to higher sugar levels. Sugar levels should be above 2.5% to improve ensilability, while cutting in the afternoon or early evening will lead to higher sugar levels.

Correct dry matter

The aim for every farmer should be to wilt grass as quickly as possible (no greater than 48 hours) and ensile it tightly in a bale or pit. Grass should be tedded out immediately after mowing, and with good weather conditions this should give a silage dry matter of close to the target 30%. Grass left in 3m rows for 48 hours will achieve close to 30% as well, with grass not tedded out and raked in 6m or 9m rows unlikely to wilt sufficiently. Wilting above 33% does not improve animal performance and is likely to lead to preservation issues. Grass should not be left greater than 48 hours after mowing as sugar levels will have dropped significantly.

Care should be taken when mowing and tedding to ensure that no soil is being taken into the cut grass, with soil bacteria affecting preservation.

Issues have been caused in recent years with dribble bars and trailing shoes leaving slurry residues present at the base of the sward. The advice would always to not spread slurry in extremely dry conditions to lessen this affect.