Maximise the value of your silage crop – Part 2

Friday 24.04.2020 , News

Continued from: Guidelines to maximise the value of your silage crop – Part 1

Utilising research from Dr. Padraig O’Kiely, formerly of Teagasc, who dedicated his work as a researcher at the Teagasc Animal and Grassland, Research and Innovation Centre in Grange, we previously focused on the long and medium-term guidelines which impact the quality of the silage made on Irish farms.

Leading on from that and with silage harvesting fast approaching, we concentrate on the shorter-term guidelines so you can optimise the quality of your silage for 2020. These centre around harvesting for optimum digestibility and successful preservation.

If a silage digestibility of 75% is required, then aim to harvest intermediate heading-date ryegrasses as seed-heads start to emerge from the grass plants. The digestibility of such crops can be expected to decrease by 2 to 3 percentage units per week once heading-out commences. Some flexibility in harvest date is usually necessary. Therefore, it is advisable to monitor the development of your crop and see if the heading date, the absence of lodging and the absence of the accumulation of dead herbage, etc., are progressing as expected.

Most years it is the weather that determines when silage will be harvested, however avoidance of mowing and harvesting under very wet conditions, particularly with leafy grass, is important. Giving the crop time to wilt will greatly assist preservation and reduce effluent output. The sward requires at least a half day and not more than 1½ days of good drying conditions. The best wilting occurs when the grass is mown after the dew has evaporated and is then placed in wide rows or is tedded. Attempting to wilt in large narrow rows or where weather conditions do not permit the crop to dry, are likely to produce herbage that will have undergone a loss in digestibility and that will make it more difficult to preserve.

Most crops do not require an additive to be applied at harvesting - with this being particularly evident with well wilted herbage, or herbage of adequate sugar content. If an additive is being applied to leafy, wet crops of low sugar content, it is important to know the ensilability of the crop (e.g. measure sugars with a refractometer), its yield (weigh strips of grass) or harvest rate, and the rate of additive to be applied. Additives such as beet pulp or citrus pulp, molasses or acid-based products, when evenly applied at appropriate rates, are most effective under ‘low sugar’ conditions.

To help achieve the air-free conditions that are necessary for good preservation and to prevent mould growth, fill the silo quickly, rolling the herbage throughout, and immediately seal it perfectly:

  • Seal immediately and properly beneath 2 sheets of black 0.125 mm polythene
  • Cover completely with a layer of car tyres, or similar, placed edge-to-edge
  • seal the edges with a layer of sandbags, silt, etc.
  • As the silage sinks somewhat in the silo during the following week or two, adjust the plastic seal to ensure no ingress of air occurs
  • Inspect the plastic cover frequently and immediately repair any visible damage

Some farmers consistently make good quality silage. Their repeated success does not indicate ‘good fortune’. They use a plan that works. It is essential to adhere to all components of a plan for successfully producing silage on your farm.

This plan is probably the single biggest contribution you can make to consistently producing silage that meets your needs.

Table 1. Silage digestibility effects on kg energy-corrected milk/cow/day, at a range of rates of concentrate input

Silage digestibility

Concentrate input (kg/cow/day)

























                                                     Source: Randby et al. (2012)

Table 2. Ensilability of grass in response to nitrogen fertiliser application               


Rate of N applied (kg/ha)




Dry matter %

Sugars (% in juice)

Buffering capacity (mEq/kg DM)







                                                                       Source: Teagasc, Grange