Making haylage while the sun shines

What is haylage?

Figure 1: Quality Oxfordshire haylage

Traditionally, horses were fed hay as a supplementary feed. Hay is grass which is cut, dried to a dry matter content of 85-90% then baled and used as a feed stuff for horses and livestock. Given the nature of the UK summer weather (frequent rain showers), and the sensitivity of horses to mould in hay that is baled slightly damp, there has been a shift from hay to haylage.

Harvesting of haylage differs in two ways:

• it is baled at a higher moisture content (60-70% dry matter content for horses), and
• the bales are wrapped in layers of plastic to create anaerobic conditions in which fermentation will occur. Consequently, haylage has higher levels of digestible protein.

 Weather is still important for haylage harvesting

While the farmer doesn’t need as long a period of sunny weather to harvest haylage, the weather during harvest is still key: haylage baled when too wet can cause potentially fatal botulism.

• Spring weather dictates roughly when the grass matures, i.e. when the crop should be cut
• Once the farmer sees the grass is almost mature, a 3-4 day window of likely ‘harvesting weather’ is sought from the 15 day weather forecast
• ‘Harvesting weather’
  • is preferably dry, with good evaporation rates (clear sky, strong sun, low relative humidity, reasonable surface wind, warm temperatures)
  • but can include the odd light shower e.g. just after cutting, so long as a dry spell with good evaporation rates follow
• As the 3-4 day harvest window approaches, higher resolution, more accurate weather forecasts can be used to confirm (or otherwise) the suitability of the forthcoming window for harvesting, and take into account what the weather next week looks like (i.e. if we wait 3 days, would there be a more confident harvesting window, or is the weather about to turn)

 The role of a weather consultant

So where is the farmer to get such weather information from?

There are a number of sites with the maps of meteorological values out to 15 days, but these do not take known biases and errors of the underlying numerical weather prediction models into account.  Nor do they tell you the likely alternative scenario should the model prove wrong, the probability of the forecast being accurate, or give a local picture.

As a trial, Lake Street Consulting worked with a local Oxfordshire farmer, monitoring the weather from the end of May until harvesting was complete, highlighting potential harvest windows and commenting on harvest plans. The early summer pattern was anything but stable, with frequent (heavy) showers, making local forecasts and use of high resolution short-term forecasts key.

• At the end of May a short dry window was flagged, along with a better window likely early June. The end of May period was deemed not to be long enough/have high enough evaporation rates (though it was suitable for harvesting wetter silage).
• The window in early June did occur, starting 8th June, and this was used to harvest the first fields.  The quantity of fields harvested was limited by threat of thunderstorms in the early hours of Sat 14th (which actually arrived late on Friday 13th).
• Another longer window was identified from Monday 16th June and enabled the rest of the crop to be harvested.

It rained in the fields to be harvested on Jun 4th, 7th, the night of 13th and 26th- 28th.

In hindsight, the window from 14th- 25th June was long enough to harvest all the haylage but it would have been over ripe by this time as the Spring weather meant early ripening.   Identifying the early harvesting window allowed top quality haylage to be harvested.

“Evaporation data may be critical!”         “Your forecast was/is spot on!!!”

Whilst the weather here has been dry recently, sunshine and showers may well return to make the second cut an equally challenging forecast!

So the role of the middle (wo)man?

Helping farmers work with the weather!