With many livestock farms facing the prospect of a fodder shortage this winter, the arrival of settled weather this week has been welcome.
Ground conditions have seen varying degrees of improvement on the back of drier conditions, allowing farmers to catch-up with harvesting second, third and fourth-cut silage.
However, making silage in September is not straightforward. Grass tends to be lower in dry matter, which has implications on ensiling, fermentation and nutritional value when fed out.
On farms with silage to cut in September, outlined are some tips to get the most out of forage harvested late in the season.
1. Make sure nitrogen is used up
Nitrogen uptake in grass growing in late summer and autumn will be slower than crops grown in June. This increases the risk of harvesting grass with higher levels of residual nitrogen in the leaf.
A high nitrate content inhibits fermentation and causes mould to develop, with fodder turning black and heating once fed out.
Use the rule of thumb that grass will use up two units of nitrogen per day from applying fertiliser to harvesting.
Note that slurry applied in late summer has a lower nitrogen availability than a spring application, which will shave a few days off the potential cutting date.
Wilting grass to increase dry matter towards 30% will reduce the risk of a high nitrate residual in grass, thereby improving fermentation.
2. Mowing
Heavy dew is common in September and standing grass tends to be soaking wet in the morning, even during a dry spell.
Mowing wet grass results in greater losses of water soluble carbohydrates, which are crucial in the fermentation process of turning grass into silage.
Therefore, if possible, aim to mow grass from late morning onwards to limit the loss of sugars. As ground conditions are still on the soft side, leaving a higher residual when mowing has advantages.
The biggest being it reduces the risk of soil contaminating grass when mowing, raking and lifting the sward. If using a contractor or someone else is mowing your grass, tell them where the wet spots are to avoid fields being cut up, mowers being damaged and grass being contaminated with soil.
3. Wilting grass
Even if grass is mown in the afternoon, dry matter will be low. Therefore, it is important to wilt grass before lifting with a harvester or baling.
That is easier said than done, as weather windows can be limited in early autumn and contractors may need to push on with work for other customers.
Ideally, leave grass on the ground for 24 to 36 hours before lifting, to increase dry matter as much as possible.
Silage at 25% to 30% dry matter will have a better fermentation, leading to less waste and higher intakes, than forages at 20% to 25% dry matter.
By leaving a higher residual when mowing grass, airflow around the cut swathe will increase, helping the wilting process. When mowing, open the swathe boards as wide as possible to spread grass out over a greater surface area to improve wilting.
Similarly, if the weather is on your side, avoid using a grouper when mowing to increase the wilting effect.
4. Tedding and raking grass
Tedding grass is another option to increase the speed that grass wilts in autumn, as shorter days and less intense sun means grass is slower to dry when compared to earlier summer. It comes at a cost though and you need to guarantee there is a good window of weather. The one occasion to avoid tedding is in swards with red clover, as the process will cause the plant to shatter.
Once grass has had an opportunity to wilt, raking swards into larger swathes is recommended. Rowing up grass will increase the area of exposed ground getting air and sunlight, helping soils to dry. As soils dry, it reduces the risk of machinery breaking the ground surface, contaminating grass in the process.
5. Be wary of high potash silage
Potassium uptake is significantly higher in autumn grass compared to early summer, so be wary of feeding silage harvested late in the year to dry dairy cows as they approach calving date. A similar principle should be applied to suckler cows with a strong dairy breeding influence and cows carrying twins.
High levels of dietary potassium so close to calving will cause metabolic issues and impact the animal’s calcium balance, ultimately resulting in more cases of milk fever. These problems are exacerbated when autumn silage has a low fibre and dry matter content.
Therefore, during the dry period, offer cows with high levels of milking potential a forage with plenty of fibre and made without a slurry application, or high potash fertiliser, prior to closing up for silage.
6. Using an additive to improve fermentation
Depending on the farm situation and the type of harvester used to lift grass, it may be beneficial to use an additive when harvesting silage in autumn.
The cost of the treatment should be outweighed by the improved fermentation and less waste fodder in the clamp.
7. Opting for bales or clamp silage?
When it comes to baling grass or ensiling in a clamp, there are various pros and cons. It ultimately depends on the farm set up, ability to handle and store silage, as well as the area of grass to be harvested.
Grass yields tend to be lower in silage harvested in autumn, making the economics of baling much more viable.
With smaller acreages, it will be easier getting a baling contractor to come at short notice than a contractor operating a self-propelled harvester and trailer outfit. Bales may also be more practical than opening an existing, covered pit to ensile a new layer of wet, autumn grass.
If fodder quality will be an issue, bales can be stacked separately and targeted to certain lower priority cattle groups.
Use these bales as soon as possible after housing, having allowed four to five weeks for grass to ferment before feeding, as they will have preservation issues.
Bigger acreages and higher yields favour clamp silage, particularly if autumn grass will be ensiled in a separate pit.
8. Stacking bales to avoid sagging
When baling silage, increase the pressure or tension on the bale chamber to pack bales more densely.
That can stop bales from sagging when stacked. As bales sag, they become deformed and air pockets form, allowing mould to grow. Wilting grass to a higher dry matter also helps bales keep their shape when stacked. Always stack bales on an area where any effluent can be collected. Don’t stack bales in field headland that will be damaged by machinery during winter.
Stack bales upright on the round end and a single row is best to stop sagging. But if space is limited, then limit stacking height to two rows, as the weight of the top bales will compress the bottom row.
9. Avoid slippage in clamp silage
Where lower dry matter silage is being ensiled, increasing chop length can help prevent the risk of slippage in the clamp.
For silage below 25% dry matter, increase chop length to around 10cm to 12cm. At dry matter between 25% and 30%, chop length can be reduced to between 8cm and 10cm.
10. Get slurry on to aftermath
Silage removes a lot of phosphate and potash from the soil, so aim to get slurry onto grass aftermath as soon as possible after harvesting.
Slurry is a great source of soil nutrients, particularly potash, helping to replace the nutrient offtake in forage.