Growth stage at harvest
The optimum growth stage to harvest a perennial ryegrass pasture for silage is when the first seed heads start to appear.
A compromise has to be made between forage quality and DM yield. DM yield will be highest when seed heads are fully developed.
However, forage quality is dropping quickly at this stage and will only support low animal growth rates or milk production.
A short closure of four weeks in spring will ensure high-quality silage. A longer closure, while increasing DM yields, may lower feed quality (see Table 4.5).
Forage quality will usually decline by 0.25-0.6 MJ/ kg DM per week of delay in silage harvest. In most regions, perennial ryegrass silage should be harvested before mid-November.
Closure dates and lengths of closure
Optimum dates and period of closure will vary with location, seasonal conditions, varietal maturity, stocking rate and availability of surplus pasture.
When to close a pasture for silage is best judged by the growth stage of ryegrass and the amount of residue remaining in a paddock after grazing . If ryegrass has 3½ or more leaves before grazing and/or a residue of >1.5 t/ha DM remains after grazing, the pasture is being under-utilised and the surplus may be closed for conservation.
Early closure is more likely with well fertilised pastures, low stocking rates, early-maturing varieties or in northern NSW and Queensland. An early harvest allows more regrowth and a quick return to grazing or a second silage harvest. There is also potential for higher total forage production.
A later closure time often requires a shorter closure period due to faster plant growth rates and rapid maturing of the pasture, but total DM production is likely to be less.
It is worth considering staggering closure dates to spread workload and risk of weather damage at harvest.
Legumes in perennial ryegrass pasture
Legumes in the pasture have potential to increase digestibility and crude protein levels of silage. However, WSC levels of the ryegrass/clover mix will be lower, making a quick, effective wilt more important. Clover-dominated pasture mixes should be harvested at the clover’s mid-flowering growth stage.
Other temperate perennial grass/legume mixtures Phalaris, cocksfoot and tall fescue are important temperate grass species, usually sown with clovers (and sometimes lucerne). Grown specifically for grazing, they have potential to produce high-quality silage. They are grown for their persistence and adaptation to a wider range of soil types and growing conditions than perennial ryegrass (see Table 4.6).
A vigorous stand of these perennial grasses can dominate the pasture’s legume component if not managed correctly.
Silage production is a valuable management tool in helping maintain a strong legume component. Producers should aim for a pasture with at least 20% legume
