Making silage depends on science and good planning - and having a crystal ball to predict the weather doesn't hurt.
Farmers should always aim to produce high-quality silage, because many things may and often do occur, meaning quality can be lower than targeted. It is important to remember the last two to three springs with wet winters or long wet spells in mid-spring that occurred just when quality pastures were ready to be harvested for high-quality silage.
Before making any silage two things should be considered: cows should never be underfed just to ensure the pit is full or a certain number of bales of silage is made; and it costs nearly twice as much per tonne of dry matter (DM) to produce and feed back silage compared with direct grazing of that same pasture.
Many farmers, having attended a Dairy Australia/Department of Environment and Primary Industries (DEPI)-funded Feeding Pastures for Profit program, can now identify when surplus pasture starts to occur much earlier than in the past and have seen the importance of high-quality silage to produce milk. They are now achieving this by cutting early, notwithstanding the poor harvesting conditions mentioned above.
It is recommended to aim for the best possible scenario, acknowledging that pugged paddocks, inclement weather, machinery breakdowns, the late arrival of contractors, poor planning etc will occur, resulting in poorer quality silage to varying degrees, some of which can be avoided/minimised and some of which cannot.
The keys to getting and keeping high-quality silage include:
1. Cut early in the season when pastures are at or near canopy closure, which is the optimum stage of growth for grazing in spring. If conditions do suit - and this will depend on soil type - and if the entire harvesting job is done well, a pasture ensiled at or slightly past grazing height will produce only marginally less milk than if that same pasture had been grazed by the cows.
Yes, yields will be low and more paddocks may need to be harvested, but this is maintaining pasture quality in these cut areas and remaining areas of the farm. Yes, the contractors will squeal because crops will be much lighter than most contractors (and many farmers) will be used to, but the contractors will be in their rights to charge a bit more money to harvest light crops to cover their costs. However, farmers will win out because the high-quality silage will produce more milk than before and, if cut early enough when the surplus is being recognised, these paddocks should not miss a rotation and regrowth will be faster, thicker and of better quality.
2. Wilt and harvest as quickly as possible and have the forage in the pit or bale within 24-48 hours, if possible, though it isn't always possible. The longer a mown crop takes to reach its target dry matter content to ensure it undergoes the most efficient fermentation, the higher the quality and DM losses. Also, an extended wilting period increases the risk of the next rainfall occurring, resulting in even higher losses.
So, early in the season, when the ground is damp, there's little heat in the sun and it's necessary to reach the target DM content as quickly as possible, how can farmers do this? Often, this is not easily achieved, but with a few management tips and appropriate equipment it is worth the punt and can be achieved by: allowing the dew to lift before mowing; tedding (see Figure 1) -- that is, spreading the mown crop as soon as possible after mowing, probably re-tedding at least the next morning once the dew has lifted, and sometimes carrying out a third tedding for baling; or mowing pastures, clovers and young lucerne stands with a flail or tyned-type mower-conditioner (see Figure 2) and cutting crops such as cereals cut at soft-dough stage, summer forages and mature lucerne with a roller-type mower-conditioner and leaving the swath as wide as possible (75-90% of the mower width); and applying a fermentation-enhancing silage additive to encourage a desirable fermentation, as the forage will most likely be slightly wetter than ideal. Each dollar spent on additive should ensure at least a $3-$4 benefit - often more, occasionally less.
3. Compact stacks and bales as densely as possible. The poorer the compaction, the greater the amount of air trapped in the stack or bale and the greater the DM and quality losses. For bulk stacks, chop material short and spread it in layers no thicker than about 150 millimetres. Roll slowly to allow the tractor weight to compact the forage. Baling slightly slower will increase bale density so set bale density as dense as possible on the baler. Chopping balers will increase density by 8-15%.
4. Seal airtight as soon as possible after harvesting. Seal stacks, don't just cover them. Try to complete rolling immediately after harvest is finished. Avoid rolling the next morning as this just "pumps" more oxygen into the stack. Rolling should keep up with forage delivery from the paddock. The plastic sheets along the stack edges must be sealed airtight; not even a double row of tyres around the perimeter achieves this. Gravel bags filled with pea gravel or washed sand are ideal for this job along bunker walls and the stack surface (see Figure 3).
Another recent innovation for sealing stacks is the use of a see-through 45-micron-thick oxygen barrier (OB) film. It is not UV-heat-stabilised and is more than 20 times less susceptible to oxygen permeation than normal 125-micron black/white (B/W) plastic sheets. It can be incorporated (co-extruded) between the black and white layers of the B/W sheets (one-step system) or placed on the stack and covered by either a heavy UV-stabilised woven net or normal B/W film (two-step). Research has shown a saving of silage of at least 10% on the tops and shoulders of stacks compared with the normal B/W sheets, if sealed well. It does cost extra but after experiencing its benefits many farmers are swinging to the two-step system.
Individually stretch-wrapped bales must have at least four layers of film applied over all the bale and six layers if the forage or stubble on which it is sitting is stalky. Experience by many operators using most continuous in-line and large square bale wrappers has resulted in them now applying six layers to ensure a reliable and robust seal. If a white/grey mould is present in the silage, air has been or is present; this must be prevented in future.
5. Repair holes immediately using specific silage patching tape. Ensure the area to be patched is clean and dry and that repair tape of a similar colour to the holed plastic is used to minimise the difference in contracting and expanding in hot/cool conditions, resulting in the seal leaking.
*Frank Mickan is a pasture and fodder conservation specialist with the DEPI, Ellinbank Centre, Vic.