Tips on Mowing and Wilting for Quality Silage

Frank Mickan is the Pasture and Fodder Conservation Specialist with the Department Environment and Primary Industries (DEPI) at Elinbank in Victoria.

Key Aims:

  • To mow early to ensure high quality silage & plentiful regrowth.
  • To wilt the crop to the desired dry matter % ASAP after mowing.
  • To compact stacks tightly, sealed within 1 – 3 days of harvesting preferably.
  • To bale tightly, sealing within 0 – 3hours of baling, ideally at storage site.
  • Fix holes ASAP after being noticed with specific silage tapes.

KEEP IN THE BACK OF THE MIND

  • Cutting a crop when sunny will yield a higher quality crop than when shady.
  • The longer the mown crop is on the ground, greater are the losses of dry matter (DM) and quality (sugars and proteins) due to plant respiration, and increased risk of rain.
  • The fresher or wetter the material, the more it is “living” and the greater the losses of DM and quality.
  • The lighter the crop the quicker the wilt.
  • The lesser the density of the swath after mowing, the faster the wilt.
  • Crops mown early in the season and without further treatment dry very well on top, to about 3 - 5 leaves depth only, in the first 24 – 36 hours!
  • Dust, mud or manure + silage = foul silage (reduced palatability and quality)!

Assuming you are after high quality silage (>9.8 MJ ME/kg DM), then you will need to harvest perennial rye grass/white clover pastures 2 – 5 weeks before normally harvesting hay. This early in the season, the ground may be damp, air temperature cool to warm, and the skies often overcast. Try to harvest at the desired DM% but if rain is coming, into it!

To harvest high quality silage, where soil types allow, may require extra machinery and some management changes in fodder conservation. The rewards are worth it! Consider working in with neighbours who have machinery that you do not have, using contractors, buying a crucial piece of machinery, etc. Forward planning (machinery serviced, fences cut, holes filled, tracks graded, tree and holes marked, harrows moved out of paddock, plastic seal on site, etc.), and communicating with others involved assists greatly.

AM Vs PM mowing:

It is true that the plant sugars are highest in the plant by mid – afternoon. However I believe that the extra wilting gained by earlier mowing, albeit at a lower sugar content level in the plants, is more than offset by the disadvantages of mowing mid-afternoon. A crop cut in the afternoon will be higher in energy (sugars) but will undergo a much shorter wilt before nightfall. These plants with higher moisture content, fueled by the dew, will have increased quality losses overnight due to their greater respiration rates. It is also highly possible that an extra day’s wilting may be required to reach the desired dry matter content. Ensiling at lower dry matter contents than desirable will result in a less favourable fermentation with some loss of quality and reduced palatability.

MOWING and WILTING

Below are 3 scenarios of preparation of the crop up to the harvesting stage depending on the machinery on hand. In all cases the suggestion is to start mowing mid-late morning, after the dew has lifted, and finish if possible, by mid-afternoon. Dews can contain 2 – 3 tonne water/ha and dries much faster from a standing crop. Operations on Day 2 should also start after the dew has lifted. Harvest based on DM% if possible, starting a fraction early to avoid harvesting over dry material later in the day. Try to harvest 24 – 36 hrs. after mowing, and avoid delaying longer than 48 hrs. The timing suggested below are ideals. Weather, crop yields, machinery break downs, labour availability, contractor arrival, etc. will dictate the practical!

DAY I

  1. Mowing only: Mow the crop with a rotary disc mower. Consider using 2 mowers to get crop cut ASAP to allow a longer wilting period.
  2. Mow + spread: Mow the crop with a rotary mower. Spread/ted the mown crop with a tedder or tedder rake as soon as possible after mowing. Travel slowly to spread all material evenly. Set tedder so that tynes do not dig into the ground!
  3. Mower-conditioner: Mow with a mower-conditioner. The tyned types are best for pastures. Leave the windrow as wide and thin as possible. May need to talk to the mower-conditioner with a blow torch! If using a roller type mower-conditioner, travel slower rather than faster to allow the conditioning rollers to have full affect. If the crop is heavy, the inner portion of swath may not be crimped if travelling too fast or rollers set too far apart.

DAY 2

  1. Mow only: Consider “flipping” the windrow if you have a suitable rake. This is not ideal and not worthwhile doing if windrows become “ropey”. If long chopping (5 - 15cm, eg.loader wagon) or precision chopping (1 - 5cm) into a stack, start late morning. If fine weather is forecast, possibly precision chop later with increased DM%. Baling is unlikely.
  2. Mow + spread:Respread once the top few leaves show signs of wilting. This tedding can be at a faster speed. Depending on weather conditions you may not need to respread on DAY 2 if long chopping. Start harvesting about late morning. If precision chopping or baling, the second and possibly even a third tedding, may be necessary. The second tedding could be done mid - afternoon on DAY 1 sometimes. Start precision chopping orbaling about early - mid afternoon.
  3. Mower-conditioner: Harvest early - mid afternoon if long chopping. If precision chopping orbaling consider starting mid - late afternoon when pasture is drier. If confident of fine weather continuing, start mid - late morning on DAY 3.


DAY 3

  1. Mow only: Rake into windrows 1- 2 hrs. before harvesting to allow further wilting of bottom material. Harvest regardless of DM as losses are now escalating dramatically.

For information on testing dry matter of silage check out another of Frank Mickans articles A Guide to testing DM in silage.